Abstract:
An inline transfer system and method are provided for the secure transport and efficient processing of substrates such as glass substrates or semiconductor devices. A rotary conveyor is provided that includes a plurality of air nozzles which inject air to move a substrate above the plurality of air nozzles without the plurality of air nozzles making contact with the substrate. At least two independent processing units are operably coupled to the rotary conveyor. Advantageously, because a plurality of substrates may be processed in parallel, greater efficiency and flexibility are provided. Because the substrate can be moved without physical contact between the structure of the air nozzles and the substrate, the transfer is secure, clean, and efficient.

Description:
BACKGROUND  
       [0001]     (a) Field of the Invention  
         [0002]     The present invention relates to an inline transfer system and method, and more particularly to an inline transfer system and method for processing glass substrates.  
         [0003]     (b) Description of Related Art  
         [0004]     In general, a transfer system operates to move a transfer body by placing the transfer body onto a conveyor and sliding the conveyor using an operating roller connected to an operating motor. The conventional conveyor system uses a motor for power to move a body and a chain, a gear, or a belt for the purpose of power transfer.  
         [0005]     The transfer system can be utilized to transfer glass substrates in manufacturing liquid crystal displays (“LCDs”) in one example. An LCD is one of the most popular flat panel displays, which includes two panels provided with two kinds of electrodes generating an electric field and a liquid crystal layer interposed therebetween. The LCD displays images by controlling light transmittance, and the control of the light transmittance is performed by applying voltages to the electrodes to generate electric fields which change the arrangement of liquid crystal molecules.  
         [0006]     The two panels of an LCD are transferred to the processing device of each manufacturing process using the transfer system to complete an LCD.  
         [0007]     Conventionally, a plurality of glass substrates is transferred to the processing device of each manufacturing process using a cassette, a stocker, and an indexer. In other words, the transfer system for a LCD manufacturing process receives a plurality of glass substrates to the cassette, stores them in the stocker, and carries them in and out to the processing device of each manufacturing process using a robot indexer.  
         [0008]     However, as glass substrates are increasing in size, a transfer system using the cassette, stocker, and indexer becomes more difficult to use because a typical cassette, stocker, or indexer transfers a plurality of glass substrates, and thus an existing cassette, stocker, or indexer must be made larger to transfer substrates of a larger size. Furthermore, several disadvantages occur in a typical transfer system with larger glass substrates, such as inefficiency, lower yield due to breaks and contamination, and lack of flexibility. Thus, there is a need in the art for an efficient and flexible system and method for processing substrates.  
       SUMMARY  
       [0009]     The present invention provides an advantageous system and method for transferring and processing fragile objects, such as glass substrates used in the manufacture of LCDs, in which cleanliness and secure transport are of high concern. A rotary conveyor utilizes a plurality of air nozzles to transport substrates without making direct contact between the air nozzle structure and the substrate, thereby allowing for clean and secure transport of the substrate. Coupled to the rotary conveyor are at least two independent processing units or at least two independent inspection devices.  
         [0010]     According to one embodiment of the present invention, an inline transfer system is provided, including a rotary conveyor including a panel, and a plurality of air nozzles operably coupled to the panel, wherein the plurality of air nozzles inject air to move a substrate above the plurality of air nozzles without the plurality of air nozzles making contact with the substrate. At least two processing units are operably coupled to the rotary conveyor, wherein the at least two processing units operate independently of each other providing operating flexibility and efficiency.  
         [0011]     According to another embodiment of the present invention, another inline transfer system is provided, including a rotary conveyor and at least two inspection devices operably coupled to the rotary conveyor, wherein the at least two inspection devices operate independently of each other. A substrate classifier for classifying the inspected substrates is operably coupled to the rotary conveyor.  
         [0012]     According to yet another embodiment of the present invention, an inline transfer method is provided, including providing a first rotary conveyor operably coupled to a first set of processing units and a second set of processing units, and providing a second rotary conveyor operably coupled to the first set of processing units and the second set of processing units. The second rotary conveyor is operably coupled to the first rotary conveyor by at least one elevator. The method further includes providing a substrate on the first rotary conveyor for processing in one of the first set of processing units and one of the second set of processing units. A determination is made whether the substrate is allowed to be processed in one of the first set of processing units, and the substrate is processed in one of the first set of processing units when allowed. The substrate is transferred to one of the second set of processing units via the first rotary conveyor or the second rotary conveyor. A determination is made as to whether the substrate is allowed to be subsequently processed in one of the second set of processing units, and the substrate is processed in one of the second set of processing units when allowed.  
         [0013]     Advantageously, the present invention allows for the secure and clean transport and processing of glass substrates and other fragile objects, resulting in higher yields with less damage and contamination. The present invention is also advantageous for providing flexibility and efficiency such that processing may occur in parallel and not be delayed when one line has a malfunction.  
         [0014]     These and other features and advantages of the present invention will be more readily apparent from the detailed description of the embodiments set forth below taken in conjunction with the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]      FIG. 1  is a schematic diagram of an inline transfer system according to an embodiment of the present invention;  
         [0016]      FIG. 2  is a layout view of an inline transfer system according to an embodiment of the present invention;  
         [0017]      FIG. 3  shows a detailed structure of a conveyor;  
         [0018]      FIG. 4  is a sectional view of  FIG. 3  taken along the line IV-IV′;  
         [0019]      FIG. 5  is a perspective view of a part of an inline transfer system according to an embodiment of the present invention;  
         [0020]      FIG. 6  is a flowchart describing the control process of an inline transfer system according to an embodiment of the present invention; and  
         [0021]      FIG. 7  is a schematic diagram of an inline transfer system according to another embodiment of the present invention. 
     
    
       [0022]     Use of the same reference symbols in different figures indicates similar or identical items. It is further noted that the drawings may not be drawn to scale.  
       DETAILED DESCRIPTION  
       [0023]     The present invention is directed to an inline transfer system and method which minimizes transfer time by controlling and transferring glass substrates one by one for processing.  
         [0024]     The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.  
         [0025]     In the drawings, the thickness of layers and regions are exaggerated for clarity. Like numerals refer to like elements throughout. It will be understood that when an element such as a layer, region, or substrate is referred to as being “on” another element, the element can be directly on the other element or intervening elements may also be present. In contrast, when an element is referred to as being “directly on” another element, there are no intervening elements present.  
         [0026]     Now, an inline transfer system according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.  
         [0027]      FIG. 1  is a schematic diagram of an inline transfer system according to an embodiment of the present invention,  FIG. 2  is a layout view of an inline transfer system according to an embodiment of the present invention, and  FIG. 3  shows a detailed structure of a conveyor.  
         [0028]     Referring to  FIGS. 1-3 , an inline transfer system according to an embodiment of the present invention includes a plurality of processing devices  100  and  200  and a plurality of rotary conveyors  300  and  400  located between the plurality of processing devices  100  and  200 . Two or more rotary conveyors are preferred.  
         [0029]     When it is supposed that N is a positive integer and the manufacturing process of an LCD is performed by (N+3) processes, a plurality of Nth processing devices and a plurality of (N+1)th processing devices are arranged on a first floor 1 and a plurality of (N+2)th processing devices and a plurality of (N+3)th processing devices are arranged on a second floor 2.  
         [0030]     For example, a CVD process and a photolithography process as the first and the second processes, respectively, are performed on first floor 1, and a sputtering process and an etching process as the third and the fourth processes, respectively, are performed on second floor 2.  
         [0031]     A first inter-floor elevator  101  that transfers a plurality of substrates  30 , e.g. a glass substrate, on which a CVD and a photolithography process are performed on first floor 1, to second floor 2 one by one is installed between first floor 1 and second floor 2.  
         [0032]     A second inter-floor elevator that transfers a substrate  30  that is placed on second floor 2 to first floor 1 one by one is also installed between first floor 1 and second floor 2.  
         [0033]     For purposes of description, the processing devices on second floor 2 in  FIG. 1  are referred to as first processing devices  100  and second processing devices  200 , respectively.  
         [0034]     As shown in  FIG. 1 , a plurality of first processing devices  110 ,  120 ,  130 ,  140 , and  150  and a plurality of second processing devices  210 ,  220 ,  230 ,  240 , and  250  are arranged opposite to one another, respectively.  
         [0035]     A first rotary conveyor  300  shaped similar to a rotary route is placed between a plurality of the first processing devices  110 ,  120 ,  130 ,  140 , and  150  and a plurality of the second processing devices  210 ,  220 ,  230 ,  240 , and  250 . The first rotary conveyor  300  is connected to entrances  110   a ,  120   a ,  130   a ,  140   a , and  150   a  and exits  110   b ,  120   b ,  130   b ,  140   b , and  150   b  of each of the first processing devices and to entrances  210   a ,  220   a ,  230   a ,  240   a , and  250   a  and exits  210   b ,  220   b ,  230   b ,  240   b , and  250   b  of each of the second processing devices and moves a plurality of the substrates  30  one by one.  
         [0036]     A first inline buffer  510  is arranged between the first rotary conveyor  300  and the entrances  110   a ,  120   a ,  130   a ,  140   a , and  150   a  of each of the first processing devices, and a first transfer body elevator  610  is arranged between the first rotary conveyor  300  and the exits  110   b ,  120   b ,  130   b ,  140   b , and  150   b  of each of the first processing devices. The first transfer body elevator  610  is also connected to the second rotary conveyor  400 . Therefore, the substrate  30  in which the first process is completed can be transferred to the first rotary conveyor  300  or to the second rotary conveyor  400  by taking first transfer body elevator  610  depending on the conditions set during manufacturing.  
         [0037]     A second transfer body elevator  620  and a second inline buffer  520  are arranged between the first rotary conveyor  300  and the entrances  210   a ,  220   a ,  230   a ,  240   a , and  250   a  of each of the second processing devices. The second transfer body elevator  620  is also connected to the second rotary conveyor  400 . Consequently, the substrate  30  being moved on the first rotary conveyor  300  can be carried into the entrances  210   a ,  220   a ,  230   a ,  240   a , and  250   a  of the second processing devices after going through the second transfer body elevator  620  and the second inline buffer  520  depending on the conditions set during manufacturing. Substrate  30  being moved on the second rotary conveyor  400  can also be carried into the entrances  210   a ,  220   a ,  230   a ,  240   a , and  250   a  of the second processing devices after going down via the second transfer body elevator  620  and going through the second inline buffer  520  depending on the conditions set during manufacturing.  
         [0038]     As shown in  FIGS. 1 and 2 , first rotary conveyor  300  includes first and second transferring units  310  and  320 , each of which is shaped as a long line opposing each other. Third and fourth transferring units  330  and  340 , each of which is shaped as a short line, connect both end portions of first and second transferring units  310  and  320 . Together, transferring units  310 ,  320 ,  330 , and  340  form a shape similar to a rotary route.  
         [0039]     A plurality of first direct transfer conveyors  350  are formed inside first rotary conveyor  300  to shorten the path that substrate  30  must travel during processing as substrate  30  moves on first rotary conveyor  300 . In other words, a plurality of the first direct transfer conveyors  350  are formed or arranged between and parallel to the third and fourth transferring units  330  and  340  to connect the first and second transferring units  310  and  320  with each other.  
         [0040]     A plurality of the first processing devices  110 ,  120 ,  130 ,  140 , and  150  and a plurality of the second processing devices  210 ,  220 ,  230 ,  240 , and  250  are arranged in a line along the first and second transferring units  310  and  320  of the first rotary conveyor  300 .  
         [0041]     Second rotary conveyor  400  is arranged apart from first rotary conveyor  300  by a specified distance. The structure of second rotary conveyor  400  is identical with that of first rotary conveyor  300 . That is, second rotary conveyor  400  includes first and second transferring units  410  and  420 , each of which is shaped in a long line opposite to each other, and third and fourth transferring units  430  and  440 , each of which is shaped in a short line connecting both end portions of the first and second transferring units  410  and  420 . Together, transferring units  410 ,  420 ,  430 , and  440  form a shape similar to that of a rotary route.  
         [0042]     A plurality of second direct transfer conveyors  450  are formed inside second rotary conveyor  400  to shorten the path that substrate  30  must travel during processing as substrate  30  is moved along second rotary conveyor  400 . In other words, a plurality of second direct transfer conveyors  450  are formed or arranged between and parallel to the third and the fourth transferring units  430  and  440  to connect the first and second transferring units  410  and  420  with each other.  
         [0043]     A plurality of rotary conveyors (not shown) may be arranged apart from second rotary conveyor  400  by a specified distance. It is preferable that the structure of each rotary conveyor is identical with that of the first rotary conveyor  300 . However, it will be apparent that rotary conveyors  300  and  400  may be shaped to follow not only a rotary route but a rectangular, square, circular, oval, or other shaped path.  
         [0044]     Referring now to  FIGS. 3 and 4 , the detailed structure of first rotary conveyor  300 , second rotary conveyor  400 , first direct transfer conveyor  350 , or second direct transfer conveyor  450 , along with the moving status of substrate  30 , are shown.  FIG. 4  is a sectional view of the conveyor shown in  FIG. 3  taken along the line IV-IV′. An example of an applicable transfer apparatus is disclosed in co-pending U.S. patent application Ser. No. ______ {Attorney Docket No. AB-1343 US}, filed on Apr. ______,  2004 , which is incorporated by reference herein for all purposes.  
         [0045]     As shown in  FIGS. 3 and 4 , first rotary conveyor  300 , second rotary conveyor  400 , first direct transfer conveyor  350 , and second direct transfer conveyor  450  each includes a support panel  10  and a plurality of air nozzles  20  that are formed on the support panel  10  and transfer the transfer body by injecting or sucking air.  
         [0046]     The support panel  10  is arranged along the transfer direction of the transfer body, e.g., a substrate  30 . In other words, support panel  10  is installed along the direct transfer direction A of substrate  30  and also along the branch direction B along which substrate  30  is carried after being branched off at the branch point. A plurality of air nozzles  20  formed on support panel  10  are arranged along direct transfer direction A and branch direction B as well. When substrate  30  is carried, air nozzles  20  are placed under substrate  30 .  
         [0047]     The plurality of air nozzles  20  and substrate  30  do not contact one another but the plurality of air nozzles  20  are placed to maintain a prescribed distance from substrate  30 . In order to do that, air nozzles  20  fix the position of substrate  30  by injecting air and forming a vacuum status inside air nozzles  20  to prevent substrate  30  from straying by the injection of air. In other words, at each air nozzle, there is simultaneous air injection impinging on the surface of the transfer object and a vacuum or suction effect, similar to a whirlpool&#39;s center, and thus the air injection “sticks” to the transfer object, thereby stabilizing the position of the transfer object.  
         [0048]     An air transfer groove can be formed inside an air nozzle  20  to form a vacuum status inside each of the plurality of air nozzles  20 . The air transfer groove can be formed to have various forms for creating simultaneous air injection and suction and in one example can be formed to be slanted or spiral in shape.  
         [0049]     The plurality of air nozzles  20  injects air from a prescribed angle (θ) in up and down directions with respect to direct transfer direction A. Accordingly, substrate  30  is moved along direct transfer direction A. In this case, since air nozzles  20  and substrate  30  do not contact one another, there is no power loss due to friction, which enhances the transfer speed while reducing noise. Furthermore, since there is no contact between substrate  30  and air nozzles  20  while transferring substrate  30 , yield is enhanced by preventing breaks and cracks due to contact during transport and by preventing contamination from particles or chemicals.  
         [0050]     As shown in  FIGS. 1-3 , first transfer body elevator  610  is arranged between exits  110   b ,  120   b ,  130   b ,  140   b , and  150   b  of the first processing devices and second rotary conveyor  400 , thereby coupling exits  110   b ,  120   b ,  130   b ,  140   b , and  150   b  of the first processing devices to second rotary conveyor  400 . In other words, first transfer body elevator  610  moves substrate  30  on which the first process is completed in first processing device  110 ,  120 ,  130 ,  140 , or  150  to second rotary conveyor  400 .  
         [0051]     The second transfer body elevator  620  is arranged between the entrances  210   a ,  220   a ,  230   a ,  240   a , and  250   a  of the second processing devices and second rotary conveyor  400 , thereby coupling entrances  210   a ;  220   a ,  230   a ,  240   a , and  250   a  of the second processing devices to second rotary conveyor  400 . In other words, second transfer body elevator  620  moves substrate  30  from second rotary conveyor  400  to second processing device  210 ,  220 ,  230 ,  240 , or  250 .  
         [0052]     First inline buffer  510  is arranged between first rotary conveyor  300  and entrances  110   a ,  120   a ,  130   a ,  140   a , and  150   a  of the first processing devices. First inline buffer  510  controls the number and therefore the amount of substrates  30  carried in to first processing device  110 ,  120 ,  130 ,  140 , or  150  by performing a buffer operation when the amount of substrates  30  carried in to first processing device  110 ,  120 ,  130 ,  140 , or  150  gets too large. In other words, buffer  510  allows substrates to be left idle for a short time before substrates are carried in to a processing device. In addition, first inline buffer  410  may inspect and remove substrates with defects.  
         [0053]     Also, second inline buffer  520  is arranged between second transfer body elevator  620  and entrances  210   a ,  220   a ,  230   a ,  240   a , and  250   a  of the second processing devices, which controls the amount of substrates  30  carried into second processing device  210 ,  220 ,  230 ,  240 , or  250  by performing a buffer operation when the number or amount of substrate  30  carried into the second processing device  210 ,  220 ,  230 ,  240  or  250  gets too large.  
         [0054]      FIG. 5  is a perspective view of a part of the inline transfer system according to an embodiment of the present invention, and  FIG. 6  is a flow chart describing the control process of the inline transfer system according to an embodiment of the present invention. The operation of the inline transfer system according to an embodiment of the present invention having a structure as described above will now be described with reference to  FIGS. 1-6 .  
         [0055]     Substrate  30  that moves to second floor 2 riding on first inter-floor elevator  101  moves riding on first rotary conveyor  300  (S 110 ).  
         [0056]     While substrate  30  moves riding on first rotary conveyor  300 , it is determined whether substrate  30  satisfies the condition that substrate  30  may be carried in to one of a plurality of the first processing devices  110 ,  120 ,  130 ,  140 , and  150  (S 120 ).  
         [0057]     If it does not satisfy the condition that substrate  30  is to be carried in to first processing device  110 ,  120 ,  130 ,  140 , or  150 , substrate  30  keeps moving on first rotary conveyor  300  (S 110 ).  
         [0058]     In the case that substrate  30  satisfies the condition that it is to be carried in to one of the first processing devices, substrate  30  is carried in to one of the first processing devices  110 ,  120 ,  130 ,  140 , and  150  (S 130 ).  
         [0059]     For example, five (5) of the first processing devices  110 ,  120 ,  130 ,  140 , and  150  are drawn in  FIG. 1 , and the first processing devices are defined as 1-1 line  110 , 1-2 line  120 , 1-3 line  130 , 1-4 line  140 , and 1-5 line  150 , respectively. As shown in  FIG. 5 , if the condition that substrate  30  is carried in to the 1-1 line  110  is satisfied while substrate  30  moves on first rotary conveyor  300 , substrate  30  is carried in to the 1-1 line  110 .  
         [0060]     The condition that a substrate  30  is carried in is the case that another substrate  30  is not carried in to the 1-1 line  110  beforehand and the 1-1 line is ready to perform the first process with a new substrate  30 . However, if another substrate  30  was carried in to the 1-1 line  110  beforehand and is in the middle of the first process, or if the 1-1 line is not ready to carry in a new substrate  30  in such cases as when the 1-1 line is under inspection, substrate  30  keeps moving as riding on the first rotary conveyor  300 . While moving, if any of the 1-1 line  110 , 1-2 line  120 , 1-3 line  130 , 1-4 line  140 , or 1-5 line  150  satisfies the condition that substrate  30  is to be carried in, substrate  30  is carried in to the line and the first process is performed. Accordingly, process flexibility is ensured, which means that even though a specific manufacturing processing device line is malfunctioning, under inspection, in use, or otherwise unavailable, it does not affect the other processing device lines and production can be continued.  
         [0061]     Then, it is determined whether the condition that substrate  30  that finishes the first process in the first processing device is to be carried in to one of the second processing devices (S 140 ).  
         [0062]     If any of the second processing devices satisfies the condition that substrate  30  is directly carried in, it is carried in to the second processing device while riding on first direct transfer conveyor  350  (S 150 ).  
         [0063]     However, if substrate  30  in which the first process is completed in one of the first processing devices  110 ,  120 ,  130 ,  140 , or  150  does not satisfy the condition to be carried in to any of the second processing devices  210 ,  220 ,  230 ,  240 , or  250 , substrate  30  is moved on second rotary conveyor  400  after being elevated to second rotary conveyor  400  by riding on first transfer body elevator  610  (S 160 ).  
         [0064]     Then, while substrate  30  is moved on second rotary conveyor  400 , it is determined whether the condition that a substrate is to be carried in to any of the second processing devices  210 ,  220 ,  230 ,  240 , and  250  is satisfied (S 170 ).  
         [0065]     If the condition that the substrate is to be carried in to any of the second processing devices  210 ,  220 ,  230 ,  240 , or  250  is not satisfied, the substrate  30  keeps moving while riding on the second rotary conveyor  400  (S 160 ).  
         [0066]     However, if the condition that the substrate is to be carried in to any of the second processing devices  210 ,  220 ,  230 ,  240 , and  250  is satisfied, substrate  30  is carried in to one of the second processing devices  210 ,  220 ,  230 ,  240 , and  250  riding on second transfer body elevator  620  (S 180 ).  
         [0067]     Then, for the substrate  30  that was carried in to the second processing device riding on first direct transfer conveyor  350  or second transfer body elevator  620 , the second process is performed in the second processing device (S 150  and S 180190 ).  
         [0068]     For example, five (5) of the second processing devices  210 ,  220 ,  230 ,  240 , and  250  are drawn in  FIG. 1  and these five first processing devices are defined as 2-1 line  210 , 2-2 line  220 , 2-3 line  230 , 2-4 line  240 , and 2-5 line  250 , respectively. The substrate  30  in which the first process is completed in the first processing device  110 ,  120 ,  130 ,  140 , or  150  is carried in to any of the 2-1 line  210 , 2-2 line  220 , 2-3 line  230 , 2-4 line  240 , and 2-5 line  250 . For example, if the condition that the substrate is carried in to the 2-1 line  210 , the substrate is carried in to the 2-1 line  210  riding on first direct transfer conveyor  350 . As shown in  FIG. 5 , it is preferable that the substrate is carried in to the 2-1 line  210  riding on first direct transfer conveyor  351 , which is located closest to the path between the 1-1 line  110  where the first process was completed and the 2-1 line  210 , among a plurality of the first direct transfer conveyors  350 .  
         [0069]     However, if substrate  30  in which the first process is completed in the first processing device  110 ,  120 ,  130 ,  140 , or  150  is not in the case that any of the 2-1 line  210 , 2-2 line  220 , 2-3 line  230 , 2-4 line  240 , and 2-5 line  250  satisfies the condition that the substrate is carried in, it moves riding on second rotary conveyor  400  after being transferred to second rotary conveyor  400  riding on the first transfer body elevator  610 . Then, if the condition that any of the 2-1 line  210 , 2-2 line  220 , 2-3 line  230 , 2-4 line  240 , and 2-5 line  250 , for example, the 2-3 line  230  satisfies the condition that the substrate is carried in, substrate  30  is carried in to the 2-3 line  230  after going down by riding on the second transfer body elevator  620 .  
         [0070]     Then, substrate  30  in which the second process is completed in second processing device  210 ,  220 ,  230 ,  240 , or  250  moves to the next process riding on second inter-floor elevator  201  or other inter-floor elevator (S 190 ).  
         [0071]     On the other hand, as shown in  FIG. 1 , in case that substrate  30  is not carried in to any of the first processing devices  110 ,  120 ,  130 ,  140 , and  150  or the second processing devices  210 ,  220 ,  230 ,  240 , and  250  and moves for a long time riding on first rotary conveyor  300  and second rotary conveyor  400  because the carry-in condition is not satisfied, it is preferable that substrate  30  is temporarily stored in an off-line buffer  900 . This off-line buffer  900  is arranged to be connected to a part of the first rotary conveyor  300  and a part of the second rotary conveyor  400 .  
         [0072]     Consequently, the present invention provides advantages in process flexibility. Although a specific manufacturing processing device line is malfunctioning or otherwise unavailable, it does not affect other processing device lines and production can be continued. Transfer time is also reduced due to the direct connection between the manufacturing processes.  
         [0073]     Furthermore, the number of substrates “in process” is dramatically reduced since the substrates are managed and transferred one by one but processed in parallel. The “work in process” is a metric used in the manufacturing field since there is continual “work in process” because the same objects are continually manufactured in a factory. Since the “work in process” held in each manufacturing process are calculated in terms of monetary amount and included in the inventory, it is advantageous that the amount of the “work in process” be reduced as in the present invention. Advantageously, the present invention provides a highly efficient transfer system in which process lines are not affected even though a specific manufacturing process is malfunctioning or in use.  
         [0074]     An inline transfer system according to another embodiment of the present invention is shown in  FIG. 7 . Same or similar reference numerals as in the drawings mentioned above indicate the same or similar parts for performing the same or similar function.  
         [0075]     As shown in  FIG. 7 , an inline transfer system according to another embodiment of the present invention is illustrated. The inline transfer system includes a plurality of first inspection devices  71 ,  72 ,  73 , and  74  and a plurality of second inspection devices  81 ,  82 ,  83 , and  84  which are arranged in two lines opposite each other.  
         [0076]     A rotary conveyor  90  shaped in a rotary route is placed between the plurality of first inspection devices  71 ,  72 ,  73 , and  74  and the plurality of second inspection devices  81 ,  82 ,  83 , and  84 . The rotary conveyor  90  is connected to the entrances  71   a ,  72   a ,  73   a , and  74   a  of each of the first inspection devices and to the entrances (not shown) of each of the second inspection devices and carries a plurality of the substrates  30  one by one. It will be apparent that rotary conveyor  90  may be shaped to follow not only a rotary route but a rectangular, square, circular, oval, or other shaped path.  
         [0077]     Rotary conveyor  90  is branched off in front of the entrances  71   a ,  72   a ,  73   a , and  74   a  of the first inspection devices in order to be connected to the entrances  71   a ,  72   a ,  73   a , and  74   a  and is branched off in front of the entrances (not shown) of the second inspection devices in order to be connected to the entrances (not shown) of the second inspection devices.  
         [0078]     Rotary conveyor  90  includes first and second transferring units  91  and  92 , each of which is shaped in a long line opposite to each other, and third and fourth transferring units  93  and  94 , each of which is shaped in a short line connecting both end portions of the first and second transferring units  91  and  92 , to form a shape similar to that of a rotary route. The plurality of first inspection devices  71 ,  72 ,  73 , and  74  and the plurality of second inspection devices  81 ,  82 ,  83 , and  84  are arranged in one line each along the first and second transferring units  91  and  92  of rotary conveyor  90 .  
         [0079]     A plurality of direct transfer conveyors  95  are formed inside rotary conveyor  90  to shorten the path that substrate  30  must travel as substrate  30  is moved along rotary conveyor  90 . In other words, a plurality of direct transfer conveyors  95  are formed between and parallel to the third and fourth transferring units  93  and  94  to couple first and second transferring units  91  and  92  with each other.  
         [0080]     A classifying conveyor  60  is connected to the entrances (not shown) of the first inspection devices and exits  81   b ,  82   b ,  83   b , and  84   b  of the second inspection devices and is also connected to entrances of a plurality of substrate classifiers  170  for classifying the substrates  30  in which inspection is completed.  
         [0081]     Referring to  FIG. 7 , an operation of the inline transfer system according to the present invention will now be described in detail.  
         [0082]     The substrate  30 , during a manufacturing process such as an LCD manufacturing process, is moved along rotary conveyor  90  connected to the plurality of inspection devices  70  and  80  in order to enter the inspection process in inspection device  70  or  80 .  
         [0083]     While moving along rotary conveyor  90  located between the plurality of inspection devices  70  and  80 , it is determined whether a condition for the substrate to be carried in to any of the first and second inspection devices  70  and  80  is satisfied. The condition that substrate  30  is carried in to one of the inspection devices  70  and  80  is the case that another substrate  30  is not carried in beforehand and, thus, the inspection process is not already in progress, or that inspection devices  70  and  80  are ready to perform the inspection process with a new substrate  30 .  
         [0084]     Substrate  30  is carried in to the inspection device that satisfies the above-referenced condition among the plurality of first inspection devices  71 ,  72 ,  73 , and  74  and the plurality of second inspection devices  81 ,  82 ,  83  and  84 , and the inspection is performed therein.  
         [0085]     Meanwhile, the substrate  30  that moves riding on the first and the second transfer units  91  and  92  of the rotary conveyor  90  is carried in to the inspection device that satisfies the carry in condition riding on the rotary conveyor  90  that is extended to the entrances of the first inspection devices  71   a ,  72   a ,  73   a , and  74   a  and the entrances of the second inspection devices.  
         [0086]     The substrate  30  in which the inspection process is completed in one of the plurality of first and second inspection devices  70  and  80  moves to the substrate classifier  170  riding on classifying conveyor  60  that is connected to the exits of the first inspection devices and exits  81   b ,  82   b ,  83   b , and  84   b  of the second inspection devices.  
         [0087]     The substrate is classified after being carried in to one of the glass substrate classifiers  170  according to the inspection grade determined in the inspection process.  
         [0088]     Advantageously, the present invention provides great process flexibility. Although a specific inspection device may be malfunctioning, it does not affect other inspection devices and the inspection process can be continued. Furthermore, transfer time is reduced since the inspection process is performed one by one and in parallel with and the inline transfer system using the rotary conveyor  90  and classification conveyor  60 .  
         [0089]     The inline transfer system according to the present invention has advantages of dramatically reducing the amount of “work in process” by controlling and transferring the substrates one by one and by reducing the transfer time by direct connection between the manufacturing processes.  
         [0090]     In addition, there is an advantage that the investment cost to the initial manufacturing processing device is reduced because it does not use a stocker, a cassette, or an indexer.  
         [0091]     Moreover, the present invention provides enhanced yield by minimizing the environmental problems due to contaminating material and quality problems due to contact because of the air floating method used for conveyance.  
         [0092]     Although preferred embodiments of the present invention have been described in detail hereinabove, it should be clearly understood that many variations and/or modifications of the basic inventive concepts herein taught which may appear to those skilled in the present art will still fall within the spirit and scope of the present invention, as defined in the appended claims.