Patent Publication Number: US-2006018737-A1

Title: Automated material handling system

Description:
BACKGROUND OF THE INVENTION  
      (1) Field of the Invention  
      The invention relates to an automated material handling system, and particularly to an automated material handling system that transports materials through a conveyer.  
      (2) Description of the Prior Art  
      With continuous advances of manufacturing technologies, the size of materials (such as wafers and glass substrates) produced in the semiconductor or photoelectric industry also increases constantly. Those materials generally are grouped in lots, and each of the lots contains 25 pieces that are loaded in a cassette for transporting. Its weight is too heavy for human to carry. Hence nowadays most plants adopt automated material handling system (AMHS) as the main facility to transport the cassettes.  
      Refer to  FIG. 1  for a conventional single loop AMHS  10 . It includes an overhead single loop track  11 . Bays  12  of various functions are setup around the tracks  11  according to manufacturing process requirement planning. The track  11  carries a plurality of overhead shutters (OHS)  13 , and each holds a cassette. The overhead shutters  13  move in and out of each bay  12  to transport materials. As the materials are transported between the bays  12 , it is generally called an Interbay transport system.  
      Each bay  12  has a stocker  14  and a plurality of tools  15 . The tools  15  in the same bay  12  are usually interrelated in the manufacturing process. Hence in the manufacturing process planning, one bay  12  may be seen as a manufacturing unit.  
      The stocker  14  mainly functions as a transfer station and a buffer zone of material handling between the overhead shutters  13  and the tool  15 . The conventional stocker  14  is a rectangular solid having two opposing long sides, and each equips with a plurality of transferring ports  141 . It has one short side connecting to the track  11 , and a crane in the center to transport materials among the transferring ports  141 . The stocker  14  has one or two transferring ports  141   a  and  141   b  close to the track  11  to serve as the material transport input and output ports to the overhead shutters  13 . The rest transferring ports  141  are connected to the tools  15  and serve as the material transport input and output ports between the tools  15  and the stocker  14 .  
      The conventional single loop automated material handling system provides only one way transport track. Control of vehicles and transport planning are simpler. Thus it is widely used in the industry. However, in practice, there are still many drawbacks, notably: 
          a. Poor transport efficiency: Due to the conventional technique transports only one way, in the event of rework is required in the manufacturing process, the materials have to be moved back to the original bay for processing. But the vehicle cannot be moved backwards directly. It has to continuously travel forwards and finish the entire journey of the track before returning to the original bay to process rework. Hence transport efficiency is undesirable.     b. When the conventional technique is adopted for one way interbay transportation of a long distance, the problem of empty vehicles occurs. This problem happens in the plant configuration that requires to set up the bays at a long distance one way. Hence vehicle dispatching has to take into account of the time required to transport the empty vehicles.     c. When the conventional technique is adopted for sectional interbay transportation, the system cost is higher. Referring to  FIG. 2 , for the sectional interbay transportation, the entire transport system is divided into several independent bay areas. Between the independent bay areas, there is no need for material transport. But to facilitate identification, different bays  12  have their numbers suffixed by different English characters. As the conventional single loop handling system  10  has to be a complete system, waste of system investment happens between the independent bay areas (as the areas shown by the broken line).     d. The conventional techniques is constrained by the number of the vehicles and cannot provide buffer zones for the working in process (WIP).     e. The transport direction of the conventional techniques is fixed, and cannot be altered or provide two-way transport function.        

      Therefore, it is desirable to provide a smoother and more efficient material handling system that can overcome the disadvantages associated with the conventional automated material handling system.  
     SUMMARY OF THE INVENTION  
      Accordingly, it is an object of the present invention to provide an automated material handling system to improve material handling efficiency.  
      It is another object of the present invention to provide an automated material handling system to prevent transport of empty vehicles.  
      It is yet another object of the present invention to provide an automated material handling system to reduce waste of system investment between independent bay areas when sectional interbay transport is adopted.  
      It is still another object of the present invention to provide an automated material handling system that provides more buffer zones to hold the materials for WIP.  
      It is a further object of the present invention to provide an automated material handling system that provides a two-way transport function to make material handling more flexible.  
      To achieve the foregoing objects, the automated material handling system according to the invention includes a plurality of bays, a continuous conveyer and a plurality of vehicles.  
      In one aspect, the bays may be arranged in a linear fashion or an annular loop according to manufacturing process planning. Each bay may be a manufacturing unit consisting of a plurality of tools and a stocker. The tools in the same bay generally are interrelated in the manufacturing process of the same manufacturing unit.  
      In another aspect, the stocker is a rectangular solid having a first long side and a second long side opposing each other that have respectively a plurality of transferring ports. A crane is located between the two sides. The transferring ports on the first long side are connected to the tools to transport materials therebetween. The second long side has at least one transferring port connecting to the conveyer to transport the materials between the vehicles and the transferring port. The crane transports the materials among the transferring ports in the stocker. Hence the stocker may serve as a material transfer station of each bay or a buffer zone.  
      In yet another aspect of the present invention, the continuous conveyer may be configured in a linear layout or a single loop layout, and adopt an overhead structure to be braced by a ceiling and the second side of the stocker. When the cassettes are carried by the vehicles, each cassette may hold one lot of materials. The vehicles are traveled on the route provided by the continuous conveyer, and the materials are transferred in the stocker of each bay.  
      The automated material handling system according to the invention includes a first bay and a second bay. The first bay has a first two-way transferring port on a second side of a stocker thereof, and the second bay also has a second two-way transferring port on a second side of a stocker thereof. A continuous conveyer is provided to perform two-way transport between the first and the second two-way transferring ports.  
      When the manufacturing process of the two bays are identical, the two bays can backup each other during the manufacturing process, and provide buffer zones. In the event that the first bay provides a upstream process and the second bay provides a downstream process, if the materials in the second bay require rework, they may be transported back through the conveyer to the first bay for rework. In addition, to prevent the conveyer from creating errors during the two-way transport, the handling system of the invention further includes a programmable logic controller and an interlock circuit equipment to link the signals of the first bay and the second bay and control the transport direction between the first bay and the second bay.  
      Another embodiment of the present invention is adopted on sectional interbay material transport. It includes a plurality of independent bay areas, a plurality of sectional conveyers and a plurality of vehicles.  
      The bay areas in the embodiment set forth above are independent from one another. Each bay area includes at least one bay and one sectional conveyer. Each bay includes a plurality of tools and a stocker. The sectional conveyer is connected to at least one transferring port located on a second side of the stocker to transport materials between the stocker and the vehicles along the travel route of the conveyer.  
      During material transport in the sectional interbay process, fabrication of the materials is finished in the bat area without the need of transporting to other bay area for processing. Hence the sectional conveyers are independent without connecting to one another. There is no need to set up transport system between the bay areas, thus waste of investment may be avoided. Moreover, since the sectional conveyers are independent, transport direction may be designed individually, either one way or two-way, without the concern of interfering with one another. Hence this embodiment is more flexible in material transport planning.  
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The present invention will now be specified with reference to its preferred embodiment illustrated in the drawings, in which:  
       FIG. 1  is a schematic view of a single loop automated material handling system according to the prior art;  
       FIG. 2  is a schematic view of a sectional Interbay transport according to the prior art;  
       FIG. 3  is a schematic view of an automated material handling system according to the first embodiment of the present invention;  
       FIG. 4  is a side view of a stocker according to the first embodiment of the present invention;  
       FIG. 5  is a schematic view of a conveyer supported by the ceiling and stocker according to the first embodiment of the present invention;  
       FIG. 6  is a schematic view of the second embodiment of the present invention; and  
       FIG. 7  is a schematic view of the third embodiment of the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      Refer to  FIG. 3  for a first embodiment of the automated material handling system  30  of the present invention. It includes a plurality of bays  31 , a continuous conveyer  32  and a plurality of vehicles  33 .  
      In an automated manufacturing process plant, the bays  31  are arranged according to the manufacturing process planning. To facilitate material transport, the bays  31  are generally configured linearly or in an annular loop. Each bay  31  may be seen as a manufacturing unit consisting of a plurality of a plurality of tools  34  and a stocker  35 . The tools  34  generally are interrelated in the manufacturing process of the manufacturing unit.  
      The stocker  35  is a rectangular solid which has a first long side  351  and a second long side  352  that have respectively a plurality of transferring ports  353 . The transferring ports  353  may be one way or two-way transferring ports. A crane  36  is located between the two sides. The transferring ports  353  on the first side  351  are connected to the tools  34  for transferring material therebetween. At least one of the transferring ports  353  on the second side  352  is connected to the continuous conveyer  32  to transfer materials between the transferring port  353  and the vehicles  33 . The crane  36  transfers the materials among the transferring ports  353 . Hence the stocker  35  may serve as a material transfer station in the bay  31 . In addition, each transferring port  353  has a plurality of buffer zones  37  laid vertically (referring to  FIG. 4 ) for transferring materials between the transferring ports  353  and the buffer zones  37 . Thus the stocker  35  may serve as the material buffer zone of the bay  31  during manufacturing process.  
      The continuous conveyer  32  may be configured in a linear layout or a single loop layout and connect to the second side  352  of the stocker  35 . As the second side  352  is the longer side of the stocker  35 , when the continuous conveyer  32  adopts an overhead structure to be braced by a ceiling  4 , it can receive more support from the second side  352  (referring to  FIG. 5 ) and has a higher stability. By contrast, if the conveyer  32  is connected to the stocker  35  on the shorter side that provides less bracing area, it receives less bracing support, and the stability of the conveyer  32  also decreases.  
      When the vehicles  33  are used to carry cassettes, each cassette may hold one lot of materials. The vehicles  33  are traveled on the route provided by the continuous conveyer  32 , and the materials are transferred in each bay  31 .  
      Refer to  FIG. 6  for a second embodiment of the invention. The automated material handling system  60  includes a first bay  61  and a second bay  62 . The first bay  61  has a plurality of first tools  611  and a first stocker  63 . The first stocker  63  has a first side  631  and a second side  632  equipping with a first two-way transferring port  64 . The second bay  62  also has a plurality of second tools  621  and a second stocker  68 . The second stocker  68  has a third side  681  and a fourth side  682  equipping with a second two-way transferring port  69 . A continuous conveyer  65  is provided to do two-way transport between the first two-way transferring port  64  and the second two-way transferring ports  69 . When the manufacturing process of the two bays  61  and  62  are identical, they can backup each other and provide a buffer zone.  
      Detailed implementation of the second embodiment is depicted as follow: when production of the first bay  61  reaches its full capacity but the second bay  62  still is idle, the buffered materials in the first bay  61  may be transported through the conveyer  65  between the two bays  61  and  62  to the second bay  62  for processing so that both bays  61  and  62  can achieve optimum production to increase the production efficiency of the whole system. On the contrary, if the second bay  62  reaches full production capacity but the first bay  61  is idle, materials may be transported through the conveyer  65  to the first bay  61  for processing.  
      The embodiment mentioned above may also be adopted to bays of different manufacturing processes as depicted below. If the first bay  61  provides a upstream process and the second bay  62  provides a downstream process, when the material in the second bay  62  requires rework, the material may be transported by the conveyer  65  to the first bay  61  to do rework. To prevent the conveyer  65  from creating errors during the two-way transport, the handling system of the invention further includes a programmable logic controller (PLC)  66  and an interlock circuit equipment  67  to link the signals of the first bay  61  and the second bay  62  and control the transport direction of the conveyer  65  between the first bay  61  and the second bay  62 .  
      Refer to  FIG. 7  for a third embodiment of the invention. It is adopted to a sectional interbay material handling system  70 . It includes a plurality of independent bay areas  71   a  and  71   b , a plurality of sectional conveyers  72   a  and  72   b  and a plurality of vehicles  73   a  and  73   b.    
      In the third embodiment, the bay areas  71   a  and  71   b  are independent from one another. Each bay area includes at least one bay  71  and a sectional conveyer  72 . Each bay  71  includes a plurality of tools  74  and a stocker  75 . The sectional conveyer  72  is connected to at least one transferring port  753  located on a second side  752  of the stocker  75 . Vehicles  73  are located on the sectional conveyer  72  which provides a travel route to transport materials between the stocker  75  and the vehicles  73 .  
      During material transport of the sectional interbay process, fabrication of the materials is finished in the bat area  71  without the need of transporting to other bay area for processing. The sectional conveyers  72  are independent without connecting to one another. Thus there is no waste of transport system between the bay areas  71 . Moreover, since the sectional conveyers  72  are independent, transport direction may be designed individually, either one way or two-way. Hence this embodiment is more flexible in material transport planning than the conventional techniques do.  
      While the preferred embodiments of the present invention have been set forth for the purpose of disclosure, modifications of the disclosed embodiments of the present invention as well as other embodiments thereof may occur to those skilled in the art. Accordingly, the appended claims are intended to cover all embodiments which do not depart from the spirit and scope of the present invention.