Abstract:
A lock device for adding and removing containers to and from a vacuum treatment chamber, wherein the device comprises carrier plates for the containers, the plates being fastened to a revolving transport means and being transported through lock channels provided in straight sections of the transport means, achieving a sealing effect with said channels. The plates are moved past suction or ventilation openings in the lock channel. In this way, a differential pressure stage can be formed. The device can be flexibly dimensioned and cost-effectively produced.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    The present application claims the benefit of priority of International Patent Application No. PCT/EP2008/010848, filed Dec. 18, 2008, which application claims priority of German Application No. 102008007629.5, filed Feb. 4, 2008. The entire text of the priority application is incorporated herein by reference in its entirety. 
     
    
     FIELD OF THE DISCLOSURE 
       [0002]    The disclosure relates to a lock device for continuously adding and removing containers to and from a vacuum treatment chamber. 
       BACKGROUND 
       [0003]    Such lock devices are required e.g. for vacuum-supported coating processes, e.g. to increase gas-tightness of PET bottles which to this end are usually treated in a vacuum of about 10 to 40 mbar. For this, continuous locking in and out is indispensible for an economical manufacturing process. 
         [0004]    A generic lock device is known e.g. from EP 0943699 B1. This lock comprises a revolving housing with a lock chamber wheel rotatably mounted therein in which lock chambers with openings for loading and unloading containers to be locked are provided on the circumference. 
         [0005]    The revolving housing comprises suction pipes for evacuating the lock chambers which are atmospherically sealed from each other by circumferential seals on the lock wheel. The lock chambers between the charging and the discharging station, respectively, in the outer room and the evacuated treatment room form a differential pressure stage, the lock chamber pressure being reduced revolving in the direction of the treatment room, from the atmospheric pressure usually prevailing in the outer room to the pressure prevailing in the treatment room. 
         [0006]    However, due to the complicated manufacture of the revolving housing and the lock chamber wheel, a subsequent adaptation of the device to different container sizes and shapes is expensive or not possible at all. To be able to also for large containers provide sufficiently large lock chambers in a number sufficient for the differential pressure stage, it is moreover necessary to correspondingly increase the diameter of the lock wheel. This involves a wide structural shape which might be undesired. 
         [0007]    Another lock device known from DE 27 47 061 A is used to lock tapes into or out of a vacuum coating chamber through a pressure stage section. The lock device comprises several fixed lock chambers arranged one behind the other and separated from each other with slit-like diaphragms. The tape to be coated is transported through the slit diaphragms and the lock chambers on a backing tape. To be able to generate a drop of pressure between the chambers, the diaphragms must be adapted to the cross-section of the backing tape and the tape to be coated. Such a device, however, is not practicable for locking in and out containers, as these, in contrast to a tape, do not comprise a constant cross-section seen in the moving direction, or as gaps between the individual bottles are inevitable. 
       SUMMARY OF THE DISCLOSURE 
       [0008]    It is an aspect of the present disclosure to provide a generic lock device which permits continuous adding and removing of containers to and from a vacuum coating room into a room with atmospheric pressure, which, however, does not comprise the aforementioned disadvantageous restrictions. 
         [0009]    This aspect is achieved with the present lock device. Accordingly, the lock comprises a revolving transport means comprising straight sections with carrier plates arranged at the transport means at distances for holding the containers, with lock channels at least partially extending along the straight sections through which the containers are transported by transport means, the carrier plates being embodied so that they achieve such a sealing effect with the channel walls that a drop of pressure can be generated in the lock channels. 
         [0010]    The lock device can be flexibly and inexpensively adapted to changed demands by exchanging the carrier plates and/or changing the distance between the carrier plates. 
         [0011]    Advantageously, a suction opening or a ventilation opening is embodied in the channel wall. Thereby, the lock channel can be evacuated or ventilated without having to provide disturbing conduits in the channel. 
         [0012]    In one advantageous embodiment, the carrier plates are, at least in sections, thicker than the clearance of the suction opening or the ventilation opening at the side facing the suction opening or the ventilation opening, so that the opening can be closed by the carrier plates. Thus, pressure compensation in the lock channel can be timed. 
         [0013]    In the moving direction of the transport means, further suction openings or ventilation openings are preferably arranged at a distance. This permits suction or ventilation with different pressures section by section. 
         [0014]    It is particularly advantageous to be able to generate step-like pressure differences between the front and rear sides of the carrier plates. This permits to displace regions of different pressures within the lock channel with the carrier plates. 
         [0015]    Favorably, the lock channel is embodied as differential pressure stage in which the pressure is reduced towards the vacuum treatment chamber. Thereby, the bottles can be stepwise adapted to the vacuum in the treatment chamber. 
         [0016]    In a particularly advantageous embodiment, the carrier plates each comprise at least one seal surrounding the edge and lying against the channel wall. Thereby, the sealing effect of the carrier plates can be improved. 
         [0017]    It is furthermore advantageous to embody the transport means in the form of two chains, toothed racks, tension bars or belts arranged one upon the other. This permits uniform power transmission to the carrier plates and prevents the plates from being inclined in the lock channel. 
         [0018]    In a particularly advantageous embodiment, the carrier plates comprise rollers which support the plates at the channel wall. It is thereby prevented that the plates are tilted or get jammed. Moreover, the rollers take care that the plates maintain an essentially constant distance to the channel wall over the complete circumference and a uniform sealing effect is thus achieved. 
         [0019]    Favorably, the carrier plates are centrically fixed to the transport means. Thereby, a moment on the support rollers can be prevented. 
         [0020]    Advantageously, the channel wall comprises plate-like lateral segments which are connected by half bowls. This permits a good sealing effect as well as an inexpensive manufacture and adaptation to different bottle sizes. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]    The disclosure will be described more in detail below with reference to a preferred embodiment represented in the figures. In the drawings: 
           [0022]      FIG. 1  shows a plan view of a preferred lock device according to the disclosure; 
           [0023]      FIG. 2  shows a diagonal view of the lock device of  FIG. 1  with an adjacent treatment chamber; 
           [0024]      FIG. 3  shows a detailed view of the lock device of  FIG. 1 ; 
           [0025]      FIG. 4  shows a diagonal view of a carrier plate with chain segments and bottles; 
           [0026]      FIG. 5  shows a schematic section in the plan view through a differential pressure lock according to the disclosure. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0027]    The lock device according to the disclosure represented in  FIG. 1  comprises a transport means in the form of two chains  3 ,  5  arranged one upon the other (in  FIG. 1 , only the upper chain  3  is represented), which move around two chain wheels  7 ,  9  in the direction of the arrow A and at which carrier plates  11  for holding bottles  13  to be treated are provided at regular distances B in an essentially orthogonal position to the moving direction. Most of the straight sections of the chains  3 ,  5  extend through lock channels  15 ,  17 . 
         [0028]    According to  FIG. 2 , the chain wheel  7  is located in an outer room  19  at normal atmospheric pressure, while the chain wheel  9  (not represented in  FIG. 2 ) is arranged in an evacuated treatment chamber  21 . The bottles  13  are supplied in a charging region  23  and removed again in a discharging region  25  (charging and discharging are not represented). 
         [0029]    In the wall  27  of the lock channel  15 , suction openings  29  are provided at a distance B to which suited pumps, e.g. vacuum pumps (not represented) are connected, so that the respective applied pressure p is reduced in the moving direction A. 
         [0030]    According to  FIG. 1 , also at a distance B, ventilation openings  31  are provided in the wall  27  of the lock channel  17 . Suited pumps can be connected to these, so that the respective applied pressure p is increased in the moving direction A. However, it is also possible to passively ventilate the lock channel  17  through the ventilation openings  31 , e.g. via suitably dimensioned connections (not represented) to the outer room  19  or via a short circuit o the inlet channel  15  to recycle the vacuum. 
         [0031]    As can be taken from  FIGS. 3 and 4 , the chains  3 ,  5  consist of chain segments  3   a ,  5   a , of which the ends are each centrically attached to the carrier plates  11 . To this end, one chain connection link  33  each is provided at the front sides (facing the moving direction A) and rear sides of the carrier plates  11 . 
         [0032]    Each carrier plate  11  comprises one clamp  35  each for holding the bottles  11  on the plate front side and on the plate rear side, as well as rollers  37  that support the carrier plates at the walls  27  of the lock channels  15 ,  17 . The carrier plate  11  furthermore comprises two surrounding grooves  39  which, as shown in  FIG. 5 , receive each one seal  41  lying against the channel wall. The distance between the grooves  41  is enlarged on the side of the carrier plate  11  facing the suction openings  29  or ventilation openings  31 , respectively. Thereby, a sealing region  43  is provided at the carrier plate  11  of which the length C (in the moving direction A) is larger than the clearance D of the suction opening  29  or the ventilation opening  31  (in  FIG. 5 , suction openings are shown by way of example). 
         [0033]    The chain segments  3   a ,  5   a  are preferably embodied as roller chains. Chain segments  3   a ,  5   a  of a uniform length can be easily manufactured with them and fixed by means of the chain connection links  33 . However, it is just as well possible to embody a transport means according to the disclosure on the basis of toothed racks, tension bars or belts. 
         [0034]    The chain wheel  7  is preferably mounted to be movable. In this manner, the tension of the chains  3 ,  5  can be adjusted. Grooves  44  into which the carrier plates  11  engage are provided at the circumference of the chain wheels  7 ,  9 , at a distance B. The chain wheels  7 ,  9  can moreover engage in the links of the chains  3 ,  5 . If toothed racks are used instead of the chains  3 ,  5 , they can be driven by means of toothed wheels. 
         [0035]    The lock channels  15 ,  17  each comprise two rectangular plates  45  which are bolted with two half bowls  47  with a semicircular cross-section. This permits a flexible, modular assembly. The resulting channel cross-section moreover permits a good sealing effect of the carrier plates  11 . The lock channels  15 ,  17 , however, could also have a different cross-section and/or be composed of a different number of individual parts or made of one piece, respectively. The lock channels  15 ,  17  are preferably made of metal, in particular of hardenable steel. 
         [0036]    The suction openings  29  of the lock channel  17  are preferably embodied as borings, but they can also have another, e.g. rectangular cross-section. In  FIG. 2 , five suction openings  29  each are arranged one upon the other. However, a different number is also possible. It is decisive that all suction openings  29  can be simultaneously closed by the sealing region  43  of the carrier plate  11 . This is also true for the ventilation openings  31  of the lock channel  19 , i.e. the suction openings  29  and the ventilation openings  31  are arranged and shaped such that the carrier plates  11  drive over them simultaneously and close them in the process. 
         [0037]    In  FIG. 2 , two groups of five suction openings  29  each are represented in the moving direction A. As is illustrated in detail in the functional description, these groups correspond to two differential pressure stages, like the two ventilation openings  31  shown in  FIG. 1 . The number of differential pressure stages, however, can be different, as is shown in  FIG. 5 . Equally, the number of pressure stages on the suction side and on the ventilation side can differ. 
         [0038]    In the embodiment represented in the figures, the pressure stages are based on the suction or ventilation through the openings  29 ,  31  in the channel wall  27 . As an alternative, however, it is also conceivable to replace the openings  29 ,  31  by an internal suction or ventilation in the lock channels  15 ,  17 , e.g. by suited conduits in the lock channels  15 ,  17  and/or in the channel wall  27 . 
         [0039]    The carrier plates  11  are preferably made of metal, such as special steel or aluminum, or of plastics, and their shape is adapted to the cross-section of the lock channels  15 ,  17 , such that a uniform sealing effect is achieved by the seals  41  or a sealing gap (not represented). 
         [0040]    The seals  41  are embodied as lip seals. The number of seals, however, can deviate from the shown embodiment upwards or downwards. As an alternative, other sealing means could be also used, or the carrier plates  11  could be adapted to the cross-section of the lock channels  15 ,  17  so precisely, that a sufficient sealing effect, including the sealing region  43 , is also achieved without the seals  41 , e.g. with a sealing gap. 
         [0041]    The carrier plates  11  are supported in the lock channels  15 ,  17  by the rollers  37 , such that the plates  11  do not tilt or get jammed and the plates  11  maintain an essentially uniform distance to the channel wall  27  over the complete circumference to achieve a uniform sealing effect e.g. with a uniform sealing gap in this manner. The represented number and position of the rollers  37  is given by way of example and depend, among other things, on the position of the suction openings  29 . Outside the lock channels  15 ,  17 , the carrier plates  11  do not have to be guided at the rollers  37 . 
         [0042]    The chain connection links  33  are arranged centrically on the carrier plates  11 . Thus, the chains  3 ,  5  centrically act at the carrier plate  11  at the top and bottom to avoid a moment on the support rollers  37 . If other drive means are employed, such as e.g. toothed racks, tension bars or belts, the connection links  33  are embodied to match these. 
         [0043]    The clamps  35  are arranged such that the bottles  13  are held between the upper chain  3  and the lower chain  5 . 
         [0044]    Below, the functioning of the lock device shown in the embodiment will be illustrated with reference to the adjacent bottles  13   a ,  13   b  shown in  FIG. 5 . Here, “adjacent” bottles means that these are subjected to essentially the same pressure in the lock channel and are separated from “non-adjacent” bottles with the carrier plates  11   a ,  11   b  by a drop of pressure. 
         [0045]    The chains  3 ,  5  are driven continuously, e.g. by a motor acting on the chain wheel  7  (not represented). At each of the suction openings  29   a ,  29   b ,  29   c , a vacuum p 1 , p 2 , p 3  is continuously applied, where p 1 &gt;p 2 &gt;p 3 . 
         [0046]    The bottles  13   a ,  13   b  to be treated are handed over to the clamps  35  of the carrier plates  11   a ,  11   b  with a suited charging station (e.g. a common star wheel) in the region  23  and transferred into the lock channel  15  on the inlet side. There, the bottles  13   a ,  13   b  are first under normal atmospheric pressure. As soon as the front plate  11   b  passes the first suction opening  29   a , the region between the plates  11   a  and  11   b  is in communication with the suction opening  29   a  and is evacuated maximally to a suction pressure p 1 , while the chain transport is simultaneously continued. This evacuation step is continued until the rear plate  11   a  drives over the first suction opening  29   a  and closes the same thereby. As the carrier plates  11  and the suction openings  29  are essentially arranged at the same distance B with respect to each other, the front plate  11   b  simultaneously drives over the second suction opening  29   b.    
         [0047]    As soon as the front plate  11   b  now passes the second suction opening  29   b , the region between the plates  11   a  and  11   b  is in communication with the suction opening  29   b  and will be evacuated maximally to the suction pressure p 2 , until the rear plate  11   a  drives over the second suction opening  29   b  and closes the same thereby. Thus, the region between the plates  11   a  and  11   b  is evacuated in two stages to this point in time, and thus a differential pressure stage is realized. 
         [0048]    This procedure can be repeated by driving over further suction openings  29  at a lower pressure, e.g. the third suction opening  29   c  shown in  FIG. 5 , until the pressure in the region between the plates  11   a  and  11   b  is lowered to the desired pressure level, e.g. that of the treatment chamber  21 . 
         [0049]    Subsequently, the bottles enter the vacuum chamber  21 , are treated there (e.g. coated while plasma is generated) and then reach the lock channel  17  on the exit side. There, the pressure between the plates  11   a  and  11   b  is gradually increased again by driving over the ventilation openings  31 . This procedure is analogue to the above-described stepwise evacuation, however with opposite signs. 
         [0050]    In contrast to the known revolving lock, the lock according to the disclosure does without any expensive components, such as a chamber rotor complicated to manufacture or the rotor housing. Instead, different differential pressure stages with essentially uniform or standardized components, such as e.g. the carrier plates  11 , can be realized and modified, if required, with the disclosure.