Patent Publication Number: US-2005115773-A1

Title: Lift for substrate

Description:
BACKGROUND OF THE INVENTION  
      (a) Field of the Invention  
      The present invention relates to a lift for a substrate.  
      (b) Description of the Related Art  
      Generally, a semiconductor substrate used for a semiconductor device or a glass substrate for a flat panel display such as a liquid crystal display (LCD) and an organic light emitting display (OLED) is transferred by a conveyor system during the fabrication of the semiconductor device or the display panel. The conveyor system includes a conveyor mounting the substrate, a driving roller moving the conveyor, and a driving motor for driving the driving roller.  
      An LCD generally includes two panels made of glass substrates and a liquid crystal layer, while an OLED includes a signal panel made of glass substrates. The LCD displays images by applying voltages to field-generating electrodes disposed on the panels to generate electric fields, which determine the orientations of liquid crystal molecules in the liquid crystal layer. The OLED displays images by applying currents or voltages to light emitting diodes that emits light depending on the currents or voltages.  
      A conventional substrate transfer system for LCDs transfers glass substrates to several process equipments. In particular, the substrates are transferred up and down with being contained in cassettes that in turn are contained in a cage of a lift.  
      Since such a batch lifting system may not be suitable for large glass substrates and an in-line system, a single-substrate lifting system that lifts one glass substrate in a lifting cycle of a lift is suggested. However, the single-substrate lifting system increases the tact time taken by the lift.  
     SUMMARY OF THE INVENTION  
      A lift for substrates is provided, which includes: a plurality of pallets for mounting the substrates and having first and second edges; a first pair of cables connected to the first edges of the pallets; a second pair of cables connected to the second edges of the pallets; and a drive unit moving the first and the second pair of cables to move the pallets upward and downward.  
      The pallets may be flexible and each of the pallets may include a plurality rolls tied in parallel.  
      The drive unit may include a drive motor and a plurality of pulleys coupled to the drive motor.  
      The pulleys may include a drive pulley directly coupled to the drive motor to be driven by the drive motor and a plurality of idle pulleys coupled to the first and the second pairs of cables.  
      The idle pulleys may include a first pulley arranged substantially horizontal to the drive pulley, second and third pulleys arranged substantially vertical to the drive pulley, and fourth and fifth pulleys arranged substantially vertical to the first pulley and substantially horizontal to the second and the third pulleys.  
      Each of (a) a first pulley, (b) one of the second and the third pulleys, and (c) one of the fourth and the fifth pulleys may include a pair of separated bodies disposed in a straight line.  
      At least one of the pulleys may include a single body.  
      The pallets may be curved with contacting circumferences of the at least one of the pulleys.  
      The pallets may move upward with being horizontally aligned and it may move downward with being vertically aligned.  
      Alternatively, the pallets may move downward with being horizontally aligned and it may move upward with being vertically aligned.  
      The lift may further include a frame containing the pallets, a fan filter provided at walls of the frame, or an exhaust disposed at a bottom of the frame.  
      The lift may further include a pair of conveyors for feeding the substrates to the pallets and for taking off the substrates from the pallets. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The present invention will become more apparent by describing embodiments thereof in detail with reference to the accompanying drawings in which:  
       FIG. 1  is a lifting system for substrates according to an embodiment of the present invention; and  
       FIGS. 2 and 3  are schematic perspective view illustrating the movement of pallets in the lifting system shown in  FIG. 1 . 
    
    
     DETAILED DESCRITPION OF THE PREFERRED EMBODIMENTS  
      The present invention now will 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.  
      Now, a lifting system according to an embodiment of the present invention will be described in detail with reference to  FIGS. 1-3 .  
       FIG. 1  is a lifting system for substrates according to an embodiment of the present invention and  FIGS. 2 and 3  are schematic perspective view illustrating the movement of pallets in the lifting system shown in  FIG. 1 .  
      Referring to  FIG. 1 , a lifting system according to this embodiment includes a lift  100  for elevating/lowering substrates  1  and a pair of lower and upper conveyors  200  and  300  for feeding on/taking off the substrates  1 .  
      As shown in  FIGS. 1-3 , the lift  100  includes a cuboidal frame  10 , a plurality of flexible pallets  40  disposed in the frame  10 , first and second pairs of cables  51  and  52  coupled to the pallets  40 , and a drive unit  60  and  70  for driving the first and the second cables  51  and  52 .  
      The frame  10  has a pair of lower and upper entrances/exits  11  and  12  disposed near its bottom and top, respectively, for receiving and discharging substrates  1 . A plurality of fan filter units (FFU)  80  for introducing clean air into the interior of the frame  10  are disposed at a sidewall of the frame  10 , and an exhaust  13  for discharging the air in the frame  10  is disposed at a bottom of the frame  10 .  
      The drive unit  60  and  70  includes a drive motor  70  and a plurality of pulleys  60  coupled to the drive motor  70 . The motor  70  is disposed out of the frame  10  for preventing the contamination of substrates  1 .  
      The pulleys  60  include a drive pulley  61  directly coupled to the drive motor  70  preferably through chains or belts (not shown) to be driven by the drive motor  70  and a plurality of idle pulleys  62 - 66  coupled to the cables  51  and  52 . The pulleys  60  are placed at the transitions of moving direction of the cables  51  and  52  or the pallets  40 . The drive pulley  61  is disposed at an upper left side of the frame  10  and the idle pulleys  62 - 66  include an upper right pulley  66 , first and second lower left pulleys  64  and  62 , and first and second lower right pulleys  65  and  63 . Each of the upper right pulley  66 , the second lower left pulley  62 , and the first lower right pulley  65  include a single body, while each of the upper right pulley  66 , the first lower left pulley  64 , and the second lower right pulley  63  includes a pair of bodies  66   a  and  66   b,    64   a  and  64   b,  or  63   a  and  63   b  disposed in a straight line and separated from each other with a distance larger than the width of the pallet  40 .  
      The cables  51  and  52  contact the drive pulley  61  to move in accordance with the rotation of the drive pulley  61 . The first pair of cables  51  contact the idle pulleys  62 ,  64  and  65  and the second pair of cables  52  contact the idle pulleys  62 ,  63  and  66 . When viewed from the axis of the pulleys  61 - 66  as shown in  FIG. 1 , the first pair of cables  51  approximately form a double-lined character “L,” while the second pair of cables  52  form a rectangle. In detail, the cables  51  and  52  approximately coincide with each other in a vertical direction between the drive pulley  61  and the idle pulley  62  and in a horizontal direction between the second lower left idle pulley  62  and the lower right idle pulleys  63  and  65 . The first and the second pairs of cables  51  and  52  then get away from each other. In detail, the first pair of cables  51  turn back around the first lower right pulley  65  to reach the first lower left pulley  64  and turn around the first lower left pulley  64  to run upward to the drive pulley  61 , while the second pair of cables  52  turn around the second lower right pulley  65  to go upward to the upper right pulley  66  and turn around the upper right pulley  66  to run to the drive pulley  61 .  
      Each pallet  40  includes a plurality of rolls  41  that are tied in parallel to be flexible. In addition, each pallet  40  has two opposite edges  42  and  43  extending perpendicular to its moving direction and coupled to the first pair of cables  51  and the second pair of cables  52 , respectively. The two opposite edges  42  and  43  include respective rolls and each of the edge rolls  42  and  43  has two end portions  42   a  and  42   b  or  43   a  and  43   b  coupled to respective cables  51  or  52  via connections.  
      The distance between the first pair of cables  51  and between the second pair of cables  52  is larger than the length of the edge rolls  42  and  43 , and the distance between the second pair of cables  52  is larger than the distance between the first pair of cables  51 . In addition, the distance between the first pair of cables  51  and the second pair of cables  52  The lower feed-on/take-off conveyor  200  is disposed near the lower entrance/exit  11  of the frame  10  and includes a support  210  and a plurality of rolls  220 . Likewise, the upper feed-on/take-off conveyor  300  is disposed near the upper entrance/exit  12  of the frame  10  and includes a support  310  and a plurality of rolls  320 .  
      The lift  100  can elevate or lower the substrates  1  by adjusting the rotating direction of the drive pulley  61 . For example, the pallets  40  elevate the substrates  1  upward when the drive pulley  61  rotates counterclockwise denoted by a reference character D in  FIG. 2 . On the contrary, the pallets  40  lower the substrates  1  downward when the drive pulley  61  rotates clockwise.  
      During the elevation of the lift  100 , the drive unit  60  and  70  moves the pallets  40  at the bottom of the lift  100  in a horizontal direction away from the lower conveyor  200  by aligning the pallets  40  to be substantially horizontal and making one edge  42  of each pallet  40  in advance of the other edge  43 . The lower conveyor  200  carries the substrates  1  on its surface and loads the substrates  1  on the horizontally-moving pallets  40  through the lower entrance/exit  11  and the feed-on process of the lower conveyor  200  is performed in a sequential manner. After loading the substrates  1 , the drive unit  60  and  70  moves the pallets  40  mounting the substrates  1  in an upward direction A from the bottom to the top by maintaining the pallets  40  to be horizontal and simultaneously moving the edges  42  and  43  of each pallet  40 . After reaching the top, the drive unit  60  and  70  moves the pallets  40  in a horizontal direction toward the upper conveyor  300  to take off the substrates  1  to the upper conveyor  300  through the upper exit/entrance  12  by maintaining the pallets  40  to be horizontal, making the edges  42  of the pallets  40  turn down around the drive pulley  61 , and making the edges  43  of the pallets  40  follow the fore edges  42 . The upper conveyor  300  loads the substrates  1  on its surface and takes away the substrates  1  from the lift  100 .  
      After taking off the substrates  1 , the drive unit  60  and  70  moves the pallets  40  downward in a vertical direction B from the top to the bottom by making the pallets  40  to be vertical and making the edges  42  of the pallets  40  in advance of the edges  43  of the pallets  40 . The drive unit  60  and  70  make the pallets  40  turn around the second lower left pulley  62  at the bottom to move in a horizontal direction C toward the lower conveyor  200  by aligning the pallets  40  to be substantially horizontal and making the edges  42  of the pallet  40  in advance of the other edges  43 .  
      The flexible pallets  40  can be curved at the transitions of their moving directions with contacting the circumferences of the pulleys  61 - 66 . Referring to  FIG. 1 , the pallets  40  are curved along the circumferences of the drive pulleys  60  when they turn their moving directions from the upward direction A to the downward direction B, from the downward direction B to the horizontal direction C at a bottom of the frame  10 , and from the horizontal direction C to the upward direction A.  
      The lowering operations of the conveyors  200  and  300 , the pulleys  61 - 66 , and the pallets  40  are performed in a reversed manner to the elevating operations thereof.  
      In the above-described lift  100 , since several pallets  40 , which are aligned parallel to a ground to mount the substrates  1 , are disposed in a height of the frame  10 , the tact time for elevating/lowering the substrates  1  is short. In addition, since the number of the parallel-aligned pallets  40  can be determined regardless of the height of the frame  10 , the tact time for elevating/lowering the substrates  1  may be hardly affected by the height of the frame  10 .  
      In addition, the sequential elevation/lowering of the substrates  1  can be adapted to an in-line system.  
      While the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art will appreciate that various modifications and substitutions can be made thereto without departing from the spirit and scope of the present invention as set forth in the appended claims.