Abstract:
The aim of the invention is to make it as easy as possible to change a spindle in a lifting device ( 2 ) for substrates, which device comprises a support ( 10 ). To this end the support is configured such that it can be made to engage the substrate holder ( 25 ) by rotation or by pivoting.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a lifting device for substrates and has a holder. 
     Such lifting devices are used, for example, during the manufacture of disc-shaped substrates, such as CDs or DVDs, in order to guide the substrates on a spindle relative to their height. With such devices, generally a plurality of spindles are provided for receiving the substrates on a rotary table. Each of the spindles is provided with a so-called spacer that surrounds the spindle and upon which are placed the respective disc-shaped substrates. In an operating position of the spindle, the support of the lifting device is brought into engagement with the spacer by a lateral movement of the entire lifting device. In this position of engagement, the spacer can be raised and/or lowered by the lifting device, and in particular as a function of whether the substrates are to be stacked upon the spindle and the spacer or are to be removed therefrom. 
     In order to bring a new spindle into the operating position for the receipt or removal of substrates, the lifting device must first be moved away from the spindle or spacer that is in engagement with the support. A new spindle is subsequently moved into the operating position, and the lifting device is brought back into the engagement position. In this connection, not only is a device for the lateral movement of the lifting device necessary, but sensors that sense the lateral position of the lifting device are also necessary, thereby increasing the susceptibility of the lifting device to breaking down. Furthermore, due to the lateral movement of the lifting device, a larger installation space is required. 
     U.S. Pat. No. 2,919,010 discloses a lifting device where an arm that carries a support is moved by a drive into contact with a substrate that is to be received, for example by means of a piston. In so doing, the support directly engages the substrate, whereby in particular with sensitive substrates damage can occur to the substrate. In order to bring the substrates into the region of the lifting device, in addition to the drive for the pivoting movement a separate drive is provided for moving the substrates. 
     DE-A-196 06 763 discloses a transport mechanism having a grasping device for holding and transporting substrates, with the grasping device being rotatable about an axis of rotation. In order to come into engagement with substrates, the grasping device is first rotated over a substrate and is subsequently moved linearly. In so doing, the grasping device is actively not only rotatable but also is driven linearly. 
     DE-A-36 28 544 discloses a magnetic holding device having magnetizable elements that are displaceable relative to one another and that are in the position due to relative displacement to adapt to the surface of the work piece. To receive the work piece, the magnetizable elements are magnetized and are secured relative to one another in order, when a magnetic force is applied, to prevent a relative displacement of the elements relative to one another. 
     Proceeding from the above mentioned state of the art, it is an object of the present invention to provide an economical apparatus that enables a spindle change in a simple and reliable manner. 
     SUMMARY OF THE INVENTION 
     Pursuant to the present invention this object is realized in that the substrate support can be brought into engagement with the substrate or a substrate holder by rotating or pivoting the substrate support, whereby the rotation or pivoting of the support is effected by a movement of the substrate holder. In this way, a simple spindle exchange is made possible without a lateral movement of the lifting device. This eliminates the drive for the lateral movement of the lifting device, as well as the sensors for sensing the lateral position, thereby eliminating the cost for these devices. The device overall requires fewer parts, thereby increasing the reliability of the device. By means of the passive rotation or pivoting of the support, there results a particularly simple control of the device, since only the movement of the substrate holder has to be precisely controlled. 
     Pursuant to one preferred specific embodiment of the present invention, the support is rotatable about a central axis. 
     To ensure that the support is disposed in a predetermined position when it is not in engagement with a substrate holder, the support is biased in a rest position. In this way, a respectively uniform engagement is achieved between the support on the one hand and the substrate holder on the other hand. 
     The biasing is preferably achieved by at least one magnet. By using as least one magnet, a biasing is achieved in a simple and reliable manner, whereby the drawbacks of mechanical devices, such as fatigue and/or failure of the mechanical parts, are avoided. Pursuant to one preferred specific embodiment of the present invention, at least one magnet is provided on a supporting arm of the lifting device and/or a plurality of magnets, especially four magnets, are provided on the support. 
     In order to provide a good engagement between the support and the substrate holder, and to thereby effect the rotation or pivoting of the support, the support is provided with preferably essentially radially projecting legs. 
     Pursuant to the presently preferred specific embodiment of the present invention, the support has a star shape with four or five legs. 
     The lifting device is advantageously furthermore provided with sensor means for sensing the lifting height of the substrate holder. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will be subsequently further explained with the aid of a preferred specific embodiment of the invention with reference to the figures, in which: 
     FIG. 1 is a schematic side view of the lifting device of the present invention; 
     FIG. 2 is a plan view of the inventive lifting device in a position of engagement; 
     FIG. 3 is a plan view of the inventive lifting device in an intermediate position. 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     FIG. 1 is a side view of a substrate handling apparatus that has a lifting device  2  and a substrate receiving device  3 . 
     The lifting device  2  is provided with an essentially vertically disposed guide bar  5 , as well as a slide carriage  80  that is linearly moveable on the guide bar and is provided with a supporting arm  7 . The slide carriage  80 , along with the arm  7 , is displaceable in a defined and known manner along the guide bar via an appropriate drive unit  6 . 
     As can be best seen in the top views of FIGS. 2 and 3, a rotatable support in the form of a star  10  is provided on an end of the supporting arm that is spaced from the slide carriage  80 . It can furthermore be seen from these plan views that the star  10  has four legs  12 . Respective curved engagement surfaces  13  are defined between the legs  12 . Magnets  15  are provided at or in the vicinity of the ends of the legs  12 . The star  10  is freely rotatably mounted about a central axis. All of the magnets  15  have the same spacing relative to the central axis. 
     Disposed on the supporting arm  7  of the slide carriage  80  is a magnet  16  that has the same spacing relative to the central axis of the star  10  as do the magnets  15 . The magnet  16  is oriented in such a way that it exerts a magnetic force of attraction upon the magnets  15 . Due to the magnetic force of attraction between magnet  16  and the magnets  15 , the star  10 , to the extent it is not rotated by an external force, is moved into the position shown in FIG.  3  and is held in this position. 
     The substrate receiving device  3  is disposed next to the lifting device  2 . The substrate receiving device  3  is provided with a rotary table  20  that is rotatable about a central axis A. Disposed on the rotary table  20  are a plurality (here  4 ) of substrate receiving units  22 , each of which has a base  23 , an elongated, rod-shaped spindle  24 , and a spacer  25  that surrounds the spindle  24 . 
     The base  23  of each substrate receiving unit  22  is seated on a surface of the rotary table  20  and is positively connected therewith. The spindle  24  of each substrate receiving unit  22  is held by the base  23  perpendicular to the surface of the rotary table  20 . 
     The spacer  25  of each substrate receiving unit  22  is provided with an essentially cylindrical body  26  having a central opening. The cylindrical body  26  surrounds the respective spindle  24  and can be displaced in height along the spindle  24 . The outer periphery of the cylindrical body has a stepped configuration, and in particular such that it is recessed between an upper and lower end. In this way, a respective circumferential flange  27  is formed at the upper and at the lower end. 
     The substrate receiving units  22  are uniformly disposed on a circular line about the central axis A of the rotary table  20 . 
     During rotation of the rotary table  20  the substrate receiving units  22  are also rotated along with the table  20 . Due to this rotation, the recessed outer periphery of a spacer  25  of one of the substrate receiving units  22  comes into contact with a leg  12  of the star  10 . Upon further rotation, the star  10 , due to the contact with the spacer  25 , is rotated into the position shown in FIG.  2 . In this position, the engagement surface  13  is in contact with the recessed outer periphery of the spacer  25 . By means of a vertical movement of the slide carriage  80  along the guide bar  5 , the star comes into contact, from below, with the upper flange  27  of the spacer. During a further upwardly directed vertical movement, the spacer  25  is raised along the spindle  24 . A raised position of the spacer  25  is indicated in FIG. 1 by dashed lines. In this raised position, a substrate, such as a CD or a DVD, can be placed upon the spacer  25 . The slide carriage  80  is thereupon lowered by the thickness of the deposited CD, so that a new CD can be stacked thereupon. This process continues until the spacer is disposed in the lowermost position, which indicates that the spindle is full. 
     In order to receive further substrates upon the substrate receiving units  22 , the rotary table  20  is rotated in order to bring a new substrate receiving unit  22  into contact with the rotary star  10 , and the process in repeated. 
     The apparatus can also be used in the reverse sequence for the removal of substrates from the spindle  24 . In this case, the spacer of a full spindle  24  is brought into contact with the star  10 . A spacer  25  is subsequently raised in steps along the spindle  24  in order to enable removal of the substrates. After the last substrate has been removed, the lifting device moves the spacer  25  down. The now empty spindle  24  is subsequently advanced and a new, full spindle is brought into engagement with the star  10 . 
     Although the present invention has been described with the aid of a preferred embodiment, it is to be understood that the invention is not limited to the specifically illustrated embodiment. In particular, other forms of the rotary star are possible. Instead of the rotary star, it would also be possible to provide a pivotable element that, via a movement of a spindle, is pivoted out of a rest position into an engagement position. After a further movement of the spindle, the engagement is released and the pivotable element is returned to the rest position, for example by means of a spring. 
     “The specification incorporates by reference the disclosure of German priority document 199 02 338.7 FILED 21 Jan. 1999 as well as European Patent Application priority document PCT/EP00/00190 filed 13 Jan. 2000. 
     The present invention is, of course, in no way restricted to the specific disclosure of the specification and drawings, but also encompasses any modifications within the scope of the appended claims.”