Patent Abstract:
Disclosed is a workpiece conveyor and delivery device for a vacuum processing plant. Workpieces are delivered from one device to another, both devices being located opposite each other and moving in relation to each other. A controllable magnet arrangement is provided on one of the devices. A moveable armature element acts as a holding device for the workpiece on one of the two devices which move in relation to each other, namely the device provided with the magnet arrangement. Magnet arrangement is driven to activate the holding device which can be deactivated for delivery of workpiece.

Full Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a Continuation of PCT Application No. PCT/CH97/00344 filed on Sep. 17, 1997. 
    
    
     BACKGROUND AND SUMMARY OF THE INVENTION 
     The present invention relates to a transport and transfer device. 
     A device of this type is known from EP-0 591 706. A workpiece in the form of a disc is fixed in a star-shaped transport arrangement by clamping it between a permanent magnet on the device and an armature piece. 
     In a transfer area to an additional transport device the armature is lifted off its seat, against the force of the permanent magnet, under control of an electromagnet so that the disc-shaped workpiece is released for transfer by means of a mechanically actuated holder on the additional transport device. 
     Conversely, that is, for transfer in the opposite direction, the armature is released by the electromagnet and placed on the workpiece clamped by a mechanically actuated holder so that it is picked up at the receiving transport device by the force of the permanent magnet. The workpiece is then released to the receiving transport device by the mechanically actuated holder. 
     The disadvantage of this design is that there is a mechanically actuated and controlled arrangement on the one device. In addition to the complex design the mechanical movements are problematic under vacuum conditions: It promotes particle formation which leads to higher workpiece reject rates. The greater the number of mechanically moved parts in the vacuum atmosphere the greater the potential for faults in the process execution which consequently impairs the reliability of the equipment. In addition this mechanical holder increases the cycle time of the overall system which ultimately increases the manufacturing and operating costs of the system and thereby the costs for the processed workpieces. 
     The objective of this invention is to eliminate the disadvantages of a device of the aforementioned type. 
     This is achieved in accordance with the present invention by fitting both arrangements which are movable relative to each other with at least one magnet, each as part of the controllable magnet arrangement, and by having said magnet with the armature part forming a workpiece holder in both arrangements, and by controlling the magnet arrangement in the transfer area in such a way that the armature of one or the other arrangement becomes holding, a device without any mechanical joints, meshing parts, etc. is achieved. This significantly improves the reliability of the device. The transfer cycle time can be significantly reduced, preferably by more than 25%, for example, as in the case of the subsequently described device, from the usual 10 sec. to less than 7.5 sec. This results in significant cost reductions, on the one hand due to the simplicity of the design, in the manufacture of a corresponding system, as well as in the operating costs and consequently the production costs of the workpieces treated by the system. 
     If workpieces, and in particular disc-shaped workpieces such as mini-disks, compact disks, hard disks, MO disks or semiconductor wafers are to be surface-masked before treatment in the system with a device according to the invention, at least one of the armature parts is simultaneously used as a masking element so that the holder, transfer function and masking can be optimally combined. In this way the aforementioned advantages can be even better realized. 
     The preferred designs of the device according to the invention, their implementation on a vacuum chamber or a vacuum treatment system as well as the basic transport and transfer techniques according to the invention, and the preferred utilization, are described below. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention is subsequently explained by means of illustrations. Illustrated are: 
     FIG. 1 is a schematic representation of the basic operating principle of the device according to the invention; 
     FIG. 2 is a schematic longitudinal cross-section of a preferred design version of the device according to the invention; 
     FIG. 3 Another design of the invention based on the representation in FIG. 2; 
     FIG. 4 Exploded view of a preferred armature design for handling a disc-shaped workpiece with center hole. 
     FIG. 5 is a schematic diagram of a treatment system with implementation of the device according to the invention and the functional units of the system; 
     FIG. 6 is a simplified perspective view showing the primary functional process elements of the system illustrated in FIG. 5; 
     FIG. 7 a  is a chamber according to the invention on the system according to FIG. 5 or  6 , with the device according to the invention shown in the receiving/transfer position; 
     FIG. 7 b  is a Chamber according to  7   a  with the device in the transport position; 
     FIG. 8 is a schematic enlarged view of the device according to the invention in the transfer/receiving position according to FIG. 7 a;    
     FIGS. 9 a  and  9   b  are a schematic view and top view of a part of the system according to FIG. 6 in the transport position (a) and in the treatment or receiving/transfer position (b). 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 schematically shows a transport arrangement  1  which, as indicated by the double arrow T, is driven inside a vacuum chamber (not illustrated). 
     Along its movement path a holder  3  for workpiece  5  is positioned in transfer area B opposite another arrangement  7  with a holder  9 . The arrangement  7  can either be stationary or also a transport device. 
     Both arrangements  1  and  7  have at least one magnet element  11  or  13  respectively. In addition a follower armature  15  is provided as a separate part for a workpiece  5  which is schematically represented as a disc with a center hole. The follower armature consists at least partially of magnetic material. When the workpiece  5  and the follower armature  15  rest on the transport arrangement  1  as shown by the dashed line at  15   a , workpiece  5  is held in place by follower armature  15  due to the interaction of magnet arrangement  13  with the follower armature  15 . If (not shown) workpiece  5  and the follower armature rest on the transport arrangement  7 , the follower armature  15  also holds the workpiece  5  in place due to the interaction between the magnet arrangement  11  and the follower armature  15 . 
     In transfer area B the magnet arrangements  11  and  13  are at least part of a controllable magnet arrangement. Under the most general aspect of the present invention the controllable magnet arrangement can be implemented by designing one and/or the other magnet arrangement  11  or  13  as an electromagnet; in an especially preferred design version the magnet arrangements  11  and  13  are designed as permanent magnets. The entire device according to the invention is then based on the utilization of permanent magnets according to FIG.  1 . However, the magnets can also be attached to armature  15  with the stationary parts of the device consequently being made of magnetic material. 
     For transferring workpiece  5  away from arrangement  1  to arrangement  7 , the permanent magnet arrangement  11  must overcome the retention force of the permanent magnet arrangement  13 . According to this invention this is solved in such a way that magnet arrangement  11  is designed with a stronger magnetic force than magnet arrangement  13 . With the follower armature  15  in position  15   a  the permanent magnet arrangement  11  represented by dash-dotted lines in position  11   a , is advanced by drive  12  toward the receiving element  3  and picks up the follower armature  15  against the retention force of magnet arrangement  13 . Preferred on the armature are detachable fixing elements  17 , for example, springy clips, detents such as spring-loaded balls that fix workpiece  5  to the follower armature  15 . Together with the follower armature  15  also workpiece  5  is picked up by magnet arrangement  11  and returned to receiving holder  9 . 
     For returning workpiece  5  and the follower armature  15  from arrangement  7  to arrangement  1 , magnet arrangement  11  is basically retracted to position  11   b  shown with dashed lines, or magnet arrangement  13  is pushed forward against the follower armature  15  (not shown) until the retention force of magnet arrangement  13  again dominates. 
     The described principle is consequently based on connecting the workpiece separably with the follower armature and to shuttle the latter between a permanent magnet on the one arrangement and a permanent magnet on the other arrangement where the magnetic force is controlled by varying the distance of the receiving magnet relative to the transferring magnet. 
     An additional, very important advantage of the procedure according to this invention is that no additional transport vehicle needs to be provided for the workpiece, neither for the transfer nor for the transport at one or both arrangements  7  or  1 . 
     FIG. 2 schematically shows a preferred design version of the present invention. This arrangement is designed for handling disc-shaped workpieces with a center hole which before treatment in the vacuum system, such as in a coating application, need to be masked in their center area as well as the peripheral area. 
     On the one arrangement  20 , as shown with the double arrow T corresponding to a transport arrangement, a holding surface  23  for workpiece  25  is provided. In the center of holding surface  23  a blind hole  27  is provided on the base on which a permanent magnet  29  is installed. Workpiece  25  is deposited on holding surface  23  where it is clamped by the magnetic follower armature  31  designed as a central mask. The periphery of workpiece  25  is clamped to transport arrangement  20  by masking ring  33  equipped with peripheral magnets  35  that also functions as an armature. 
     The central follower armature  31  holds the workpiece  25  by means of spring clips  37 . Spring-loaded balls can be used in place of spring clips. 
     The second arrangement  40  comprises a cylinder  42  with a termination plate  43  that forms a holding surface  44 . A piston  46  glides within the cylinder space of cylinder  42 . Permanent magnets  50  and  52  are installed at a central protrusion  48  and a peripheral ring protrusion  49 . Through the movement s of piston  46  and appropriate recesses in termination plate  43  of cylinder  42  the magnets  50  and  52  are positioned immediately into the area of surface  44  or retracted from the latter as illustrated. Arrangement  40  is also a transport arrangement in which cylinder  42  is the end of a transport plunger arrangement, T 40 . A plunger piston  54  glides inside cylinder space  56  which is installed together with a drive cylinder space  57  for a piston  58  and piston  46  in housing  60 . 
     Magnets  52  and  50  are preferably stronger than magnets  35  and  29 . 
     For transferring workpiece  25  from the illustrated position on arrangement  20  to arrangement  40 , the entire cylinder  42  is moved forward against workpiece  25  and armature  33  or  31  by means of the piston/cylinder arrangement  54 / 60  with piston  46  in the illustrated forward position, until the force of magnets  50 ,  52  is sufficient to draw the armatures  33 ,  31  together with workpiece  25  to surface  44 . The workpiece, held by armatures  31 / 33  can then be transported by arrangement  40 . 
     Conversely, for returning workpiece  25  with armatures  33 / 31  to the arrangement  20 , piston  46  and magnets  50 ,  52  are retracted from the position shown in FIG. 2 by means of the piston/cylinder arrangement until the force of magnets  35 / 29  overcomes the retention force of the retracted magnets  50 / 52 . After the transfer the transport can continue with arrangement  20 . 
     In this way a very simple transport and transfer device is created that is based solely of the effect of preferably permanent magnets whose interaction with the magnetic follower and fixing armature for the workpiece is controlled by the corresponding effective distances. 
     Of course, it is also possible to design one of the two arrangements  40  or  20  illustrated in FIG. 2, preferably arrangement  20 , as a stationary device, for example, as a feeding-opening area for a treatment chamber. In this case the holding and masking armatures  33  or  31  are, of course, reversed, as shown schematically at  31   a  with dashed lines, and in particular the central area of surface  44  and piston  46  are designed to accommodate the central prolongation of central mask  31 . This constellation is schematically illustrated in FIG.  3 . In view of what has been said so far, no further information is needed. The processing effect is schematically shown with Q. 
     When several armature elements are used as shown, for example, in FIG. 1,  2 , or  3 , one and/or the other armature can be fitted with holding devices in the form of spring clips or ball detents illustrated at  17  in FIG. 1, depending on the design. 
     The procedure according to the invention achieves not only an elegant transport and transfer technique as described further above, but as has been demonstrated additional masking steps in the system are avoided and as has been mentioned eliminates the need for an additional transport vehicle that “accompanies” a workpiece such as the aforementioned disks through the system. This increases the reliability of the system, and the cycle times are shortened by at least 25% in comparison with systems in which a separate masking step is necessary. 
     FIG. 4 is an exploded view of a preferred design of the follower armatures  41  and  43  with respect to a workpiece  45 . On the central follower armature  43  at least one ball detent  47  is provided as a holder for workpiece  45 . A permanent magnet  49  that is part arranged on the follower armature  43  is part of the magnetically active material. 
     FIG. 5 shows a system with transport and transfer device according to the invention. Illustrated are: 
       51 : Belt conveyor for the workpiece discs  52 ; 
       53 : Transport robot; 
       55 : Two-armed transport arrangement in a vacuum chamber (not shown), pivotable around its axis as shown in S 55 , where parts of the transport and transfer device according to the invention are mounted on both arms designed as plungers; 
       57 : A loading station for the follower armatures according to the invention which are inserted into the transport arms of transport arrangement  55  through a corresponding opening in the vacuum chamber (not illustrated); 
       59 : A load lock chamber; 
       61 : A main transport chamber of the system with several process chambers  63 . 
     FIG. 6 shows process chambers  63 , one of which is open. They are flanged to a main transport chamber  61 . In the main transport chamber  61  a rotary transport star  65  is provided with a number of plungers, each of which is equipped with elements for transport and transfer in accordance with the invention. Through an opening the workpiece discs are shuttled by the two-armed transport arrangement  55  in the direction of the arrow as shown in FIG. 4 by means of the armatures  41  or  43  which function as masks. arrows as shown in FIG. 4 by means of the armatures  41  or  43  which function as masks. 
     FIG. 7 a  shows the two-armed transport arrangement  55  in the corresponding transport chamber  71  as it interacts with the main transport chamber  61 . At the transfer opening  73  a load lock  59  is integrated, possibly also one on opening  74 . In accordance with the position of FIG. 7 a  and with respect to FIG. 2 the transport plungers  42  are extended and together with the corresponding openings in chamber  71  constitute a seal. Pistons  46  are also extended and together with the corresponding magnets  50 ,  52  (not shown in FIG. 7) fix the workpiece discs and their follower armatures (not shown here). In this position the transport arrangement cannot be pivoted but is locked in the transfer/receiving position. With the one illustrated plunger of transport arrangement  65  in the main transport chamber  61  a workpiece with the corresponding follower armatures is picked up from or returned to transport arrangement  55 . 
     The same applies with respect to the pick-up or transfer of a workpiece at the second chamber opening  74 . As can be seen in the transfer area to the main transport chamber  61 , both plungers acting on this opening with the corresponding opening edge function as a seal in such a way that the opening itself, through the thickness of its wall, functions as a lock chamber. The lock valves are implemented through the corresponding plungers. 
     When pistons  46  are still extended as shown in FIG. 7 b , plungers  42  are retracted so that arrangement  55  is in the pivotable transport position. 
     In FIG. 8 the two plungers on transport arrangement  55  according to FIG. 7 are shown in more detail. Both plungers are extended and seal at the corresponding opening edges. As indicated by arrow S 461  the left-hand piston is retracted momentarily in conjunction with a plunger of the main transport arrangement  61  which means that workpiece  52  with the corresponding follower and masking armatures  41 ,  43  shown in FIG. 4 are transferred to the plunger on the main chamber side. At the same time piston  46  on the right-hand plunger is extended as shown by arrow S 462  and picks up a workpiece  52  with the corresponding follower armatures  41  or  43  functioning as masks. 
     As can be seen from FIGS. 7 and 8, the forward movements of pistons  46  provided at several plungers of a transport arrangement, can be controlled independently of each other which may be desirable also for the movement of plungers  42 . 
     FIG. 9 schematically shows the transport position (a) of the plungers on the main transport arrangement  65  according to FIG. 6 as well as in the treatment position or transfer position according to diagram (b). By observing FIG. 9 b  the flow-through cycle for workpieces becomes apparent: 
     In A an untreated workpiece is picked up from  55 ; 
     In B a treated workpiece is transferred from  61  to  55 ; 
       55  is pivoted; 
     Said treated workpiece is output at A and at B the treated workpiece is transferred to  61 ,  61  is pivoted further. 
     As can be seen on the right-hand side of FIG. 8 the workpiece discs in position A can be further transported without being accompanied by the masking and follower armatures. Looking back at FIG. 9 these pass through the treatment cycles of the workpieces several times and are replaced at arrangement  91  only as required and after relatively many treatment cycles for which A purpose transport arrangement  55  is pivoted into the intermediate position shown in FIG. 9 b  with dash-dotted lines.

Technology Classification (CPC): 8