Abstract:
A vacuum coating unit having a pair of side by side transport devices for transporting substrates in a transport direction. Each transport device includes at least one first endless conveyor running in the transport direction and having a conveying element guided around at least two guide rollers or pulleys. The conveying element is located at a distance from a guide device extending in the transport direction parallel to the conveying element in such a way that the ends of the substrates can be introduced into the gap between the conveying element and the guide device of the transport devices and can be moved in the transport direction by the displacement of the conveying elements.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a national stage filing under section 371 of International Application No. PCT/EP2007/056990, filed on Jul. 9, 2007, and published in German on Jan. 10, 2008 as WO 2008/003792 and claims priority of German application No. 10 2006 031 826.9 filed on Jul. 7, 2006, the entire disclosure of these applications being hereby incorporated herein by reference 
     BACKGROUND ART 
     A vacuum coating unit with a transport device for transport of substrates in a transport direction is described below. 
     The described transport device is suitable for moving substrates through a vacuum coating unit in order to coat them, etch them or treat them in vacuum in some other way. Such vacuum coating units typically have lock chambers as well as a vacuum chamber arranged between the lock chambers, which can be divided into compartments with different functions, for example, pump compartments and process compartments. 
     During transport through the vacuum chamber, the substrates can be rotated in one embodiment of the described transport device around their own respective axis. In another embodiment, the rotation speed of the substrates can be chosen independently of the transport speed of the substrates in the transport direction. Several transport devices of the described type can be arranged one behind the other in the transport direction so that the substrates being transported are transferred without interruption from one transport device to the transport device arranged behind it. Transport devices of the described type can be arranged next to each other, viewed in the transport direction, so that elongated substrates, for example, tubes, can be brought into effective connection with each of the ends of the tubes connecting with one of the two transport devices. 
     Substrates can be fed in batches into the transport device. Conventional, temperature-sensitive bearings can be dispensed with so that the transport device can also be used for transport of substrates through high-temperature areas of a vacuum coating unit. In another embodiment defects of the transport device can be automatically recognized. An embodiment with substrate holders permits transport of different types of substrates without modification of the transport device. 
     BRIEF SUMMARY OF THE INVENTION 
     A vacuum coating unit with a transport device for transport of substrates in a transport direction includes at least one first endless conveyor arranged running in the transport direction with an endless conveying element guided around at least two guide pulleys, the endless conveying element is arranged with a spacing to a guide device running parallel to the conveying element of the first endless conveyor in the transport direction so that the substrates can be introduced into the spacing between the conveying element of the first endless conveyor and the guide device and moved by movement of the conveying element of the first endless conveyor in the transport direction. 
     Endless conveyor according to the present teaching is to be understood to mean a device that has an endless conveying element extending around at least two return pulleys. The conveying element of the endless conveyor can be an endless cable, for example, an endless belt with any cross section (circle, trapezoid, etc.), an endless belt (belt with a flat rectangular cross section) or an endless chain. The conveying element can be designed as a stainless steel cable for use in high-temperature areas of the vacuum coating unit. An endless conveyor of the mentioned type can include several conveying elements, for example, two endless stainless steel cables guided over the same guide pulleys. The stability of the endless conveyor can thus be increased, on the one hand, and its reliability improved, on the other hand, since the conveying element is designed redundant and on failure of one conveying element the second conveying element is still available. 
     In one embodiment, two of the described transport devices are arranged parallel and side-by-side, as viewed in the transport direction, in the vacuum chamber of a vacuum coating unit. The conveying elements of the endless conveyors of the two transport devices, in this variant, are each an endless steel cable and the guide devices are each a rail arranged parallel to the steel cable of the corresponding endless conveyor with a spacing between the rail and the cable. The distance between the steel cable and the rail being chosen so that the substrates being transported or the substrate holding devices provided to hold the substrates can be introduced in this spacing. 
     The substrates can be tubes to be coated. Each of these tubes is arranged transversely to the transport direction, specifically so that each end of a tube lies in the spacing between the steel cable and the rail of one of the two endless conveyors. In an illustrative embodiment, the distance between the two transport devices arranged side-by-side, i.e., their relative spacing transverse to the transport direction, is adjustable, making it possible to transport elongated substrates of different length through the vacuum chamber of the vacuum coating unit. 
     If the endless conveyors are put in operation, the sections of the steel cables of the two transport devices facing the rails are moved relative to the corresponding rails. Because of this cable movement, the two ends of the tubes that are clamped between a steel cable and a rail are caused to rotate so that the tube rolls on the two rails and in this way the tube is transported in the transport device through the vacuum coating unit. The tubular substrate is rotated around its longitudinal axis while, at the same time, being transported through the vacuum chamber so that uniform coating on all sides can be achieved. Instead of a rail or similar static guide device, the guide device of each transport device can also be a second endless conveyor arranged with a spacing to the first endless conveyor so that the transport device includes at least one pair of endless conveyors. 
     In one embodiment the distance between the conveying element and the guide device is adjustable so that the transport device can be adapted for use with different substrates. In another embodiment, substrate holding devices to accommodate the substrate are provided. Such substrate holding devices can have, for example, a first, conveyor-specific cylindrical end whose diameter is chosen so that it can be introduced into the spacing between the conveying element and the guide device, and a second substrate-specific end, configured so that it can be connected to a special substrate. For the case just mentioned, in which the substrates are tubes, the substrate-specific end could be cylindrical, the diameter being chosen so that it corresponds to the inside diameter of the tube. The substrate-specific end could also be noncylindrical, for example, have a square cross section or be provided with a clamping device. 
     Another embodiment provides that the guide device is also an endless conveyor so that each transport device includes at least one pair of endless conveyors. In this case, a first endless conveyor and a second endless conveyor are arranged running parallel to each other at a spacing in which the spacing between them corresponds to the diameter of the substrates being transported or to the conveyor-specific cylindrical end of a substrate holding device or in which the spacing between the first endless conveyor and the second endless conveyor of a transport device is adjustable. It can also be provided that the two first and second endless conveyors arranged at a spacing to each other of a transport device be controllable independently of each other. Through this embodiment, the rotational speed of the substrate can be chosen independently of the translatory transport speed through the vacuum chamber. 
     For example, depending on the speed difference of the two endless conveyors it is possible to have the substrates rotate forward or backward. In the same manner, it is possible in this embodiment to transport the substrates without rotation by operating the two endless conveyors at the same speed. It is also possible to cause the substrates to rotate without moving them in the transport direction. Moreover, the ratio of rotatory and translatory movement of the substrates along the transport path can be dynamically varied, by driving the first and second endless conveyors of a transport device accordingly. 
     For example, it is therefore possible to move substrates through the lock areas or so-called pump compartments that serve to maintain the process vacuum and vacuum separation between adjacent process compartments in purely translatory fashion, i.e., without a rotatory component, while the substrates are moved in the process compartment stationary with purely rotatory movement, i.e., without a translatory component in order to achieve uniform coating on all sides. By arranging several equivalent transport devices one behind the other, it is possible to temporarily store subsequent substrates by stopping a first transport device in a buffer zone, while the substrates situated ahead in a second transport device are coated in a process compartment, etched or treated in some other way. After completion of treatment, the substrates can be removed from the process compartment and the following substrates moved from the buffer zone and into the process compartment. 
     It can also be provided that the conveying elements of the two endless conveyors or transport device are deflected at several sites so that the substrates on their path through the vacuum chamber are moved up and down along the transport device. With this embodiment, good frictional engagement between the conveying elements and the substrates is ensured over the entire length of the endless conveyors. Deflection of the conveying elements can be produced, for example, by firmly arranged or elastically mounted pressure rollers, which are arranged along the transport direction in alternating arrangement so that they deflect the conveying element of an endless conveyor in a direction toward the conveying element of the other endless conveyor. Because of this the conveying elements of the two endless conveyors of a transport device initially run with a spacing that is less than the diameter of the substrates or the substrate holding devices. If the substrate or the substrate holding devices are introduced into the spacing and transported between the conveying elements, the distance between the two conveying elements is widened by the substrate or substrate holding devices to the necessary spacing. The pressure rollers arranged on both sides in alternation force a deflection of the substrate or substrate holding device so that the substrate or receiving device is moved back and forth, across the transport direction, in alternation during movement along the transport direction. 
     In the example just described, in which two pairs of endless conveyors are arranged so that one end of a substrate can be introduced into the spacing of each pair of endless conveyors of the transport device, this embodiment produces an improvement in frictional engagement between the substrate and the two conveying elements and at the same time alternating up and down movement of the substrate during transport through the vacuum chamber along the transport device. 
     When two or more transport devices are arranged one behind the other in the transport direction, it can be provided that the conveying elements of adjacent endless conveyors overlap so that one guide pulley of each of the two endless conveyors are mounted to rotate so that they have a common axis of rotation. In a modification, a common guide pulley can be provided, designed so that it simultaneously acts as guide pulley for two endless conveyors. Substrates can thus be transferred from a first transport device to a second transport device arranged behind it. 
     To recognize emergencies, a monitoring device can be arranged on at least one guide pulley. Such a monitoring device can include two contact elements, one of which is mounted on the guide pulley. The other contact element is fixedly arranged in the vicinity of the guide pulley so that during each revolution of the guide pulley contact between the two contact elements occurs. As soon as the guide pulley no longer rotates, for example, because the conveying element is torn, the absence of contact between the two contact elements can be recognized. 
     In another embodiment, a transport cart, having a number of receptacles, is provided to accommodate the substrates. Such a transport cart can have a frame, for example, in which upward open recesses are provided in two opposite cross arms of the frame at uniform spacings, in which one end of a substrate or substrate holding device can be inserted. The transport cart can have wheels in order to facilitate its transport through the vacuum chamber. The transport cart can also have its own drive device. 
     The transport cart can be designed so that the substrate receptacles are arranged at the same height level as the spacing between the conveying element and the guide device of a transport device arranged in the interior of the vacuum chamber of the vacuum coating unit. Because of this arrangement, the substrates or the substrate holding devices can be introduced without additional expedients into the spacing between the conveying element and the guide device, and, in this way, brought into effective connection with the transport device when the transport cart equipped with the substrates is introduced into the vacuum chamber. 
     The transport cart can be moved in the transport direction by the translatory movement produced by the transport device on the substrates or substrate holding devices received in the substrate receptacles of the transport cart. When the transport cart has its own drive device, this drive device can be operated so that the transport cart is moved by the action of the drive device synchronously with the movement of the substrates in the transport device through the vacuum chamber. 
    
    
     
       BRIEF DESCRIPTION OF DRAWING FIGURES 
       The described transport device is further explained below by means of practical examples and corresponding drawings. In the drawings 
         FIG. 1  shows a transport device with a static guide device, 
         FIG. 2  shows a transport device with two endless conveyors, 
         FIG. 3  shows a transport device with rigidly mounted pressure rollers, 
         FIG. 4  shows a transport device with elastically mounted pressure rollers, 
         FIG. 5  shows two transport devices arranged one behind the other in the transport direction, 
         FIG. 6  shows a transport cart, 
         FIG. 7  shows a substrate holding device for a tubular substrate, and 
         FIG. 8  shows a monitoring device. 
     
    
    
     DETAILED DESCRIPTION 
     The practical example in  FIG. 1  is a transport device with an endless conveyor and a static guide device arranged at a spacing  41  to it. The endless conveyor includes two guide pulleys  11 ,  12 , one guide pulley of which is a drivable drive roller  11 , as well as a conveying element  2  in the form of an endless stainless steel cable. The static guide device is a rail  3  fixedly installed within the vacuum chamber of the vacuum coating unit. In this practical example, tubular substrates  51 , which are arranged transversely to the transport direction  42 , are transported through the vacuum chamber. For this purpose, the tubular substrates  51  are initially introduced into the spacing  41  between the stainless steel cable  2  and rail  3 . 
     The spacing  41  is chosen so that the tubular substrates  51  are securely held between the stainless steel cable  2  and the rail  3 . The drivable guide pulley  11  is driven in the direction of rotation shown by arrow  13 . Because of the coupling between the two guide pulleys  11 ,  12  caused by the stainless steel cable  2 , the second guide pulley  12  is also rotated in the direction of rotation shown by arrow  13 . Because of friction between the stainless steel cable  2  and the tubular substrates  51 , the substrates are rotated in the direction of rotation shown by arrow  52 . The tubular substrates  51  therefore roll on rail  3  so that they are moved in a linear movement through the vacuum chamber in the transport direction  42 . 
     As shown in  FIG. 2 , the transport device with a first endless conveyor has a second endless conveyor arranged parallel to the first endless conveyor with a spacing  41  therebetween, which acts as a guide device. Both endless conveyors include two guide pulleys  11 ,  12 , one guide pulley  11  of which is drivable. The driven guide pulleys  11  of the two endless conveyors are controllable separately, independent of each other. In the illustrated example, the upper endless conveyor is driven more quickly than the lower endless conveyor, as indicated by the arrows  13  of different length, which show the direction of rotation at rotational speed of the guide pulleys  11 ,  12 . 
     The tubular substrates  51  arranged between the two endless conveyors are moved by the movements of conveying element  2  of both endless conveyors in the transport direction indicated by arrow  42 . At the same time, the tubular substrates  51  because of the speed difference between the two endless conveyors are placed in rotation indicated by arrow  52 . If the upper endless conveyor would be driven more slowly than the lower endless conveyor, the tubular substrates  51  would rotate in the opposite direction of rotation. In the practical example, both endless conveyors are driven so that the part of the corresponding conveying element  2  in contact with the tubular substrates  51  is moved in the transport direction  42 . However, it should be mentioned that operational types are also possible in which one of the endless conveyors is driven in the opposite direction. The substrates  51  are moved in the transport direction  42  as long as the speed of this endless conveyor is lower than the speed of the other endless conveyor. 
     In the transport device illustrated in  FIG. 3 , two endless conveyors are arranged with a spacing  41  between them, which corresponds to the diameter of the tubular substrates  51 . The spacing between the conveying elements  2  between the guide pulleys  11 ,  12  of the endless conveyors is reduced by several pressure rollers  61  which are installed fixed, i.e., rigidly. The pressure rollers  61  are arranged in alternation on the conveying elements  2  of both endless conveyors so that the substrates  51  are moved upward and downward during movement through the gap  41  existing between conveying elements  2  when they pass by the pressure roller  61 . 
     The frictional engagement of the tubular substrates  51  with the two conveying elements  2  is reinforced by the pressure roller  61  and the reduced spacing  41  of the two conveying elements  2  relative to each other. The rotational speed indicated by arrow  13  of the guide pulleys  11 ,  12  is equally large in the endless conveyors so that the tubular substrates  51  are not placed in rotation. In order to keep the tension of the conveying elements  2  of both endless conveyors constant, it is useful in this practical example to mount at least one of the guide pulleys  11 ,  12  of each endless conveyor elastically. 
     The practical example in  FIG. 4  differs from the one just described in that the pressure rollers  61  are elastically mounted on spring  62  so that the tension of the conveying elements  2  of both endless conveyors is kept constant. The rotational speed of guide pulleys  11 ,  12  of both endless conveyors indicated by arrows  13  is different so that the tubular substrates  51  are placed in rotation as indicated by arrow  52 . 
     Two equivalent transport devices are arranged one behind the other in  FIG. 5 . Each transport device again consists of an upper and lower endless conveyor. The areas of effect of the endless conveyors arranged one behind the other overlap in the area of the transition between them. For this purpose the conveying elements  2  of the consecutive endless conveyors are passed over a common guide pulley  14 . As an alternative, separate guide pulleys could be provided in this area. The separate guide pulleys, however, could have a common axis of rotation. The separate guide pulleys could thus be mounted on the same axle. 
     The conveying element  2  of each endless conveyor in the practical example of  FIG. 5  is passed over a total of six guide pulleys, two guide pulleys  12  ensuring that contact of the conveying element with the tubular substrates  51  or substrate holding devices for substrates  51  is produced, one guide pulley of which is a common guide pulley  14  above the endless conveyors, two tension rollers  15  to maintain the tension in the conveying element and two other guide pulleys  11 ,  12 , one guide pulley  11  of which is drivable, which are responsible for reversal of the conveying element  2 . 
     A transport cart is shown in  FIG. 6  which is designed to accommodate a number of substrates  51 . For this purpose, the transport cart has a frame with two longitudinal cross arms  71 , each of which is provided with a number of substrate receptacles  72  which are designed as upward open recesses. The recesses  72  are designed so that substrate holding devices can be inserted into the recesses  72  to receive elongated substrates  51 . Additional supports for the substrate holding devices are not provided. 
     The transport cart may have four wheels  73 . The transport cart can be equipped outside of the vacuum coating unit with the substrates  51  to be treated in the vacuum and then introduced to the interior of the vacuum chamber through a lock. For this purpose, ten elongated substrates  51  are either directly inserted with each end into one of two oppositely arranged substrate receptacles  72  corresponding to the number of substrates receptacles  72  arranged in pairs or connected on each end to a substrate holding device and then inserted into the transport cart so that each substrate holding device is supported on a substrate receptacle  72 . 
     A receiving device suitable for this purpose is shown as an example in  FIG. 7 . In the illustrated example, the substrate holding device is a rotationally symmetric part having several sections. The conveyor-specific end  81  is cylindrical and provided to extend beyond the longitudinal cross arm  71  of a transport cart and to enter into effective connection with the conveying element  2  of an endless conveyor and a guide device. The substrate-specific end  84  is also cylindrical and designed to be inserted into the end of a tubular substrate  51 . 
     Between the conveyor-specific end  81  and the substrate-specific end  84  there is a support section  82  with which the substrate holding device can be inserted into the substrate receptacle  72  of the transport cart. Between the support section  82  and the substrate-specific end  84 , a stop  83  is arranged, which bounds the support section  82  on the one side and ensures a defined spacing between the end of the tubular substrate  51  and the support section  82 , on the other side. 
       FIG. 8  shows a monitoring device for recognition of defects of an endless conveyor. A guide pulley  12  is mounted to rotate on a bearing block  91 . The guide pulley  12  has a first contact element  92  on its side facing bearing block  91 , which in the illustrated example is a spring steel sheet mounted on guide pulley  12 . Electrically insulated from the bearing block  91  and therefore from the guide pulley  12 , a second contact element  93  is fixed on the bearing block  91 . The second contact element  93  is designed as a flexible steel pin in the illustrated example. The flexibility is achieved by the fact that this steel pin  93  is a piece of stainless steel cable pressed into a mount. 
     When the endless conveyor is placed in operation, the guide pulley  12  begins to rotate. During each revolution the spring steel plate  92  passes by the flexible steel pin  93  once. Contact between the spring steel plate  92  and the flexible steel pin  93  then occurs. In this way, the two contact elements  92 ,  93  form a simple mechanical switch which closes a circuit on contact of the contact elements  92 ,  93 . If no switching process is recorded, despite the endless conveyor being engaged, this means that the guide pulley  12  is no longer rotating, from which it can be concluded that the conveying element  2  of the endless conveyor is defective. The described monitoring device is robust, can withstand high surrounding temperatures and is insensitive to possibly undesired coating of the contact elements  92 ,  93 , since these automatically mutually clean each other on each revolution.