Abstract:
A conveyor system includes a transfer section conveyor arrangement for quickly transporting glass sheets from a furnace conveyor to a glass processing apparatus and accurately positioning the glass sheet for further processing. The conveyor system includes specially designed locator pads, which are designed to engage the glass sheet, upon the glass sheet exiting the furnace. The locator pads are designed to engage and properly align the glass sheet for the bending process. The pads are driven by a gearing apparatus, which allows conveyance in two substantially perpendicular directions of motion so that the glass sheet can be properly aligned in the press bending molds.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention relates generally to transporting glass sheets, and more particularly, to an improved system for aligning glass after exit from a heating furnace in preparation for subsequent processing such as a press bending.  
           [0002]    Glass sheets are commonly used for vehicle windows such as side windows, rear windows and windshields. The glass sheets are bent to precisely defined shapes as dictated by the configuration and size of the openings and the overall styling of the vehicles in which the windows are to be installed. The invention would typically be used in conjunction with windshields, which are typically laminated subsequent to the pressing operation. In addition, the windows may be tempered to increase their resistance to damage resulting from impact and, in the event of breakage, to fragment into relatively small harmless particles as opposed to the large, jagged, potentially dangerous pieces otherwise resulting from untempered glass sheets when broken. The bent and tempered windows must meet stringent optical requirements whereby they are free of surface defects and optical distortions that would interfere with clear vision therethrough.  
           [0003]    One process that has been successful in producing bent, tempered vehicle windows from glass sheets is the horizontal press bending technique. This technique generally includes heating pretrimmed flat sheets of glass to their softening or bending temperatures by advancing them on a roll conveyor through a heating furnace, bending the heated glass sheets to a desired curvature or shape between a pair of complementary mold members and then tempering the same by chilling the bent glass sheets in a controlled manner to a temperature below the annealing range of glass.  
           [0004]    Glass sheet heating furnaces generally have an elongated refractory chamber through which the glass sheets are conveyed in succession upon a furnace conveyor. Heat is provided by suitable gas or electric heating elements positioned in the roof and side walls to heat the interior of the furnace. The furnace walls and roof are stationary members built up of refractory blocks. The furnace conveyor includes a series of spaced rolls extending across the furnace transverse to the direction of motion of the glass sheets. Each of the conveyor rolls includes a circumferentially outer surface which cooperates with the outer surfaces of the adjacent conveyor rolls to form a conveying surface for supporting the glass sheets and moving them through the furnace.  
           [0005]    Once the glass sheet has been heated to the optimum temperature, the heated glass sheet is transported out of the furnace to the press bending apparatus on a transfer section conveyor. It is important that the glass sheet be at the optimum temperature when it reaches the bending apparatus. If the temperature of the glass sheet is too cool, it will not be sufficiently soft for expedient and proper bending. On the other hand, if the glass sheet is overheated, it will be too pliable and will tend to sag out of the desired shape beyond the prescribed tolerances after bending. However, after the glass sheet exits the furnace it begins to cool. It is desirable to transport the heated glass sheet to the press bending apparatus quickly to minimize the cooling.  
           [0006]    When the glass sheet reaches the press bending apparatus, it is received by the mold members for bending. The glass sheet must be precisely aligned with the mold members to bend the sheet within acceptable tolerances. Therefore, it is desirable to accurately position the glass sheet with respect to the mold member for proper alignment. It is known to use stops which stop the moving sheet when it has reached a predetermined location in alignment with the mold members as disclosed by Herrington, et al (U.S. Pat. No. 4,952,227). However, aligning the glass sheet with stops may cause the moving sheet to rebound off of the stops and out of alignment before it is received by the mold members.  
           [0007]    U.S. Pat. No. 5,403,369 to McMaster et al. discloses an apparatus for positioning heated glass sheets. A positioner is mounted longitudinally and laterally movable with respect to a mold. Engagement members of the positioner engage the periphery of the glass sheet upstream of the mold and transport the glass sheet downstream to the mold.  
           [0008]    U.S. Pat. No. 5,066,321 to Kramer et al. discloses a positioning device for catching a hot glass sheet in a glass sheet heating furnace. The positioning device catches and the decelerates the glass sheet.  
           [0009]    U.S. Pat. No. 5,411,128 to Vild et al. discloses an apparatus and method for positioning a heated glass sheet on rolls. A positioner positions the glass sheet while out of contact with the rolls.  
           [0010]    U.S. Pat. No. 4,802,904 to Boutier et al. discloses a process for bending glass plates into convex shapes. Side engaging positioning devices engage the glass sheet to position it for press bending.  
           [0011]    U.S. Pat. No. 5,902,366 to Schnabel Jr. et al. discloses a glass locating system including a locating assembly that receives a glass sheet. The device includes arms entering the conveyor area from the opposing sides, each arm including first and second locators. The locators are rotatively driven to control the location of the glass sheet.  
           [0012]    High levels of precision are required for locating the glass with respect to the pressing operation. Glass oriented improperly results in wastage and therefore lowered economic efficiency. Recent developments in automotive glass lead to the use of thinner glass and more complex designs. Both of these factors increase the need for the precise locating of glass entering the forming operation, as allowable tolerances continue to decrease.  
         SUMMARY OF THE INVENTION  
         [0013]    The present invention relates to an improved conveyor system including a transfer section conveyor arrangement for quickly transporting glass sheets from a furnace conveyor to a glass processing apparatus and accurately positioning the glass sheet for further processing.  
           [0014]    In accordance with the present invention, there is provided a glass sheet transport and locating system for proper positioning of a glass sheet exiting the furnace conveyor and entering the forming operation. The forming operation preferably utilizes known press bending molds and techniques for forming the glass. The locating system includes a transfer section conveyor arrangement to convey the glass sheet from the furnace to the press bending molds. The transfer section conveyor preferably utilizes a known hot air flotation process to convey the glass to the press bending molds. Flotation systems are preferred for the transfer section because this minimizes the frictional contact with the glass sheet, thus allowing the glass to be positioned extremely accurately with minimal force required along the glass edge. Additionally, however, the system can operate with known roller systems to convey the glass from the furnace to the forming operation. The conveyor includes a first axial control located adjacent and sequentially after the furnace conveyor and a second axial control operating in conjunction with the first axial control. Each of the axial controls includes a driving system with gearing to orient the glass sheet in the desired position for press bending. The system utilizes at least two locator pads to orient the glass sheet for entering the pressing operation. Thus the conveyor system preferentially engages the glass sheet subsequent to the exit of the glass sheet from the furnace conveyor.  
           [0015]    The invention also relates to an improved method of transporting glass sheets from a furnace conveyor to a processing apparatus for further processing. The glass sheets are moved from the furnace and engaged by a locating system including first and second axial controls. Sensing means, e.g. a photoelectric eye, senses the exit of the glass sheet from the furnace and engages the locating system. The locating system includes drives and gearing for controlling orientation of the glass sheet in two axes within a plane. The locating system uses a pair of locator pads to control the positioning and motion of the glass sheet with respect to the conveyor. The glass is engaged by the locating system and properly oriented for the processing apparatus. The preferred processing apparatus is a press bending apparatus including a female ring member and male mold member having opposed complementary shaping surfaces conforming in curvature to the desired shape of the glass sheets when bent  
           [0016]    Various objects and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiment, when read in light of the accompanying drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]    [0017]FIG. 1 is a plan view of a glass processing apparatus in accordance with the invention.  
         [0018]    [0018]FIG. 2 is a sectional view taken along line  2 - 2  in FIG. 1.  
         [0019]    [0019]FIG. 3 is a plan view of one of the tracks of the transfer section in accordance with the invention.  
         [0020]    [0020]FIG. 4 is an elevational view of the track of the transfer section shown in FIG. 3.  
         [0021]    [0021]FIG. 5 is a plan view of a locator pad and the associated mechanism in accordance with a preferred embodiment of the invention.  
         [0022]    [0022]FIG. 6 is a sectional view taken along line  6 - 6  in FIG. 3.  
         [0023]    [0023]FIG. 7 is a sectional view taken along line  7 - 7  of FIG. 3.  
         [0024]    [0024]FIG. 8 is a plan view of an alternate embodiment of the glass locator pads.  
         [0025]    [0025]FIG. 9 is a plan view of another alternative embodiment of the glass locator pads. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0026]    There is shown in FIG. 1 a locating system  10  for a glass processing system. The locating system  10  is designed to engage a sheet of glass  12  upon its exit from a furnace  14 . The glass sheet  12  is conveyed from the furnace  14  to an air flotation system  18  by prepress rollers  16 . The air flotation system  18  carries the glass sheet  12  to a pressing system  20 , wherein the glass is formed into its desired shape. Upon exiting the pressing system  20 , a shuttle  60  is provided to remove the pressed glass sheet from the pressing system  20 .  
         [0027]    More detail of the pressing system  20  is shown in FIG. 2. In a conventional pressing system, a vacuum male mold  52  is located above a female ring mold  54 . In a preferred embodiment of the present invention, the female mold  54  is made primarily of a steel or stainless steel material. The female mold can also be made of a ceramic material. The male mold  52  is driven by a motor  56 , with an associated gear system  58 , toward the female mold  54 , and the glass sheet  12  is thus pressed between the molds  52 ,  54 . The gear system  58  is preferably a rack and pinion system. Alternative pressing devices are possible within the scope of the present invention. Subsequent to the pressing operation, a shuttle  60  can be used to remove the pressed glass sheet from the pressing area.  
         [0028]    The total processing system can include further processing steps (e.g. chilling), which are not germane to the present invention and are not further discussed herein.  
         [0029]    The locating system  10  includes 2 tracks  22  which are substantially mirror images of one another. The tracks  22  control the position of locator pads  24 , which control the position and orientation of the glass sheet  12  as it progresses along the air flotation system  18 . The locating system  10  engages the glass sheet  12  upon its exit from the furnace  14 , and preferably as the leading edge of the glass sheet  12  exits the prepress rollers  16 . The locating system  10  conveys the glass sheet  12  to the pressing system  20  where the locator pads  24  disengage from the glass sheet  12 , so that the glass sheet can be pressed. It is significant that these pads disengage from the glass sheet  12  during the pressing process in order to minimize breaking of the glass sheets  12 . Upon disengagement, the locator pads  24  are then moved along the tracks  22  to their original position for engaging another sheet  12  exiting the furnace  14 .  
         [0030]    The locating system  10  works by simultaneous motion of the locator pads  24  in two directions of motion. First, the pads are moving along rails  22  in direction D 1 , which is also the direction of the glass sheet  12  as it exits the furnace  14 . A sensing system, e.g. a photoelectric eye (not shown) detects the glass sheet  12  exiting the furnace  14  and, through a computerized control system (not shown), causes the locator system  10  to rapidly accelerate in the direction of travel D 1 . The computer control system also directs the locator system  10  to move arm  34  transverse to the rails  22  to thus move the locator pad  24  in the direction D 2 . It should be noted that the pads  24  move in toward the glass sheet  12 , thus the direction of travel D 2  will be reversed 180 degrees for the pad  24  on the opposing side of the glass sheet  12 . This movement in direction D 2  causes the pads to engage the glass sheet  12 , and through the unique contact surface, orient the glass sheet in the proper position for press bending. Preferably, upon contact between the locator pads  24  and the glass sheet  12 , the locators are moving at a slightly faster speed in direction D 1  than the glass sheet  12 , and catch up to the sheet after it exits the furnace. Alternatively, it can be designed so that the locator system  10  moves at the same speed as the glass sheet or slower than the glass sheet, allowing the glass sheet to catch up to the locator system for positioning.  
         [0031]    [0031]FIGS. 3 and 4 illustrate one of the rails or tracks  22  upon which the locator pads  24  move. In order to allow movement in both direction D 1  and direction D 2 , the system employs two drive assemblies  36 ,  38 . It has been found that the system preferably incorporates two essentially separate drive mechanisms, in order to allow the entire carriage assembly to move toward the pressing device, while simultaneously moving the pads into contact with the glass sheet to properly orient the glass sheet. Therefore, drive system  36  utilizes a first servomotor  40  and to drive the locator pad in direction D 2  (and also 180 degrees from direction D 2  to return the locator to its starting position.) In a preferred embodiment (see FIG. 5) the drive assembly  36  utilizes motor  41  to drive a rack  44  and pinion  46  gear system (see FIG. 5) to drive the pads  24 . While a rack and pinion system is illustrated herein, other known types of gearing or linkage systems may be utilized to drive the pad with arm  34  in direction D 2  and in the opposite direction of direction D 2 .  
         [0032]    The second drive assembly  38  uses carriage motor  40  in conjunction with a right angle gearbox  42  to drive a rack  48  and pinion  50  (see FIG. 7) to thus drive the carriage (and the pads) in direction D 1  (and in the opposite direction of direction D 1 .) Again, the nature of the gearing system is not essential to the invention. The rack and pinion system utilized herein describes a preferred embodiment. Any gearing system allowing transport of the pads  24  in the proper direction is acceptable.  
         [0033]    Thus the two drive assemblies  36 ,  38  in combination provide for motion of the pads in both directions D 1  and D 2 . This allows the pads  24  to both travel with the glass sheet  12  in direction D 1 , and to also travel transverse to the glass sheet  12  in direction D 2  (or opposite direction D 2  for the opposing pad).  
         [0034]    [0034]FIG. 5 illustrates an embodiment of the pad  24  and part of the support mechanism, in conjunction with the present invention. The present invention operates by choosing a uniquely shaped portion of the periphery of the glass sheet  12 , and designing a locator pad  24  to specifically engage with this uniquely shaped portion and thus orient the glass sheet  12  for entry into the glass pressing operation.  
         [0035]    As shown in this embodiment, pad  24  includes a first section  26  substantially parallel to the rail  22 . This section  26  does not engage the glass sheet  12 . The locator then includes a substantially straight section  28 , proceeding at an acute angle from the section  26  toward the rail  22 . Another substantially straight section  30  then proceeds from section  28  at a less acute angle toward the rail  22 . A final section  32  then projects away from the rail  22 . The shape of this locating surface, as discussed above, is preferably chosen based upon the shape of the glass sheet  12  to be press bent. Other shapes of pressing surfaces are suitable for different glass sheets.  
         [0036]    This Figure and FIG. 6 also depict additional detail of an embodiment of the gearing system. Connecting the motor  40  and the rack  44  and pinion  46  system is the square drive shaft  62 . Pinion support rollers  64  support the rack and pinion system, and guide rollers  66  provide support for the gearing system and the arm  34 . A shaft bearing  70  provides additional support for the shaft, as do bottom support rollers  68 .  
         [0037]    [0037]FIG. 8 discloses an alternative embodiment of locator pads  124 , designed for use with a differently shaped glass sheet  112 . The locator pads  124  include a first contact face  125 , which engages a side of the glass sheet  112 , and a second contact face  127 , which engages the rear of the sheet  112 . As with the previously described embodiment, the pads  124  move toward the glass sheet  112 , until contact is made to engage the sheet  112  on the contact faces  125 ,  127 . As opposed to the embodiment shown in FIG. 1, this embodiment engages the sides and the trailing edge of the glass sheet  112  instead of the sides and leading edge of the sheet  112 . Since the pads  124  do not engage the leading edge of the glass sheet  112 , deceleration of the sheet  112  by the pads  124  can be preferably initiated by frictional contact between the side contact faces  125  and the sheet  112 .  
         [0038]    In order to hold the sheet  112 , the contact faces  125 ,  127  of the locator  124  form an obtuse angle, to fit the trailing edge of the glass sheet. Again, the surfaces  125 ,  127  of these pads are designed to uniquely fit a specified area of the sheet  112 , in order to properly orient the glass sheet  112  for alignment in the press bending molds.  
         [0039]    An additional embodiment of the locator pads  224  is shown in FIG. 9. In this embodiment, the pads  224  again engage the sides and the leading edge of the glass sheet  212  by contact faces  225  and  227  of the pads  224 . In this embodiment, face  225  of the pad  224  engages the side of the glass sheet  212 , while face  227  of the pad  224  engages the leading edge of the glass sheet  212 . Again, the faces  225 ,  227  form an obtuse angle with respect to one another. It should be noted in this embodiment that surface  227  makes contact only over a relatively small part of its surface with glass sheet  212 . This is because the pads  224  engage the glass sheet  212  from the sides, while simultaneously traveling in direction D 1 . This provides clearance for the contact surfaces  227  to clear the sides of the glass sheet  212  and then to contact the leading edge of the glass sheet  212 , for control of the glass sheet  212  as it enters the pressing molds. It has generally been found that the best results for the invention have been attained where the contact between the glass sheet and the locator pads has been limited to as small a surface area as possible.  
         [0040]    In accordance with the provisions of the patent statutes, the principles and mode of operation of this invention have been described and illustrated in its preferred embodiment. However, it must be understood that the invention may be practiced otherwise than specifically explained and illustrated without departing from its spirit or scope.