Abstract:
A process for cutting glass sheets ( 10 ) includes the steps of: scoring each glass sheet on an automatic scoring table ( 12 ) having a scoring head ( 14 ) moveable on a bridge ( 16 ) and a track ( 18 ); transporting each scored glass sheet to a breaking table ( 22 ) via conveyor ( 20 ); floating each scored sheet on a fluid medium on the breaking table; and impacting each scored sheet from above the floated scored sheet to fracture the scored sheet along the score lines ( 40  and  44 ). An apparatus for cutting glass sheets includes mechanisms for performing the steps of this process. The fluid medium may be air with the impacting performed by a vacuum workholder ( 26 ) consisting of an arm ( 30 ) raised and lowered by pneumatic cylinders ( 32 ), the arm supporting a plurality of vacuum cups ( 28 ) engaging the workpiece ( 42 ) for subsequent transportation.

Description:
This application claims the benefit of Provisional application Ser. No. 60/111,544, filed Dec. 9, 1998. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to the scoring of glass and frangible workpieces, and particularly, to improvements in breaking the workpieces along the score lines and transporting resulting products. 
     2. Background Information 
     Frangible workpieces, such as glass products, are often scored to obtain the desired shape of the final product. Scoring entails cutting a groove, called a score line, partially through the thickness of the workpiece with the score lines defining the general shape of the final product. The scoring is generally performed with a sharp metal cutting wheel. Following the placement of scoring lines, the product is separated from the remaining sections of the workpiece along the score lines in a process commonly called breaking. The breaking of the scored workpiece entails generating a fracture through the thickness of the frangible workpiece within the score line which propagates along the score line. For the sake of clarification, “breaking” within the context of this application refers to this fracturing along the score lines as opposed to the destruction of the workpiece. The breaking represents a critical step in defining the resulting edge of the product. Without a clean breaking procedure the product edge will not be sharp and well defined and may require a significant amount of subsequent processing, such as grinding. A poor break may also result in an unusable workpiece (here the workpiece may be considered “broken” in the generic sense of the word) resulting in yield loss in the overall process. 
     The scoring may be performed manually using hand-held scoring implements. For products made from large sheets, the process is commonly automated by scoring, also referred to as cutting, the large sheet or workpiece on an automated cutting table having a movable scoring or cutting head. In such automated cutting tables the movable cutting head is often controlled by a CNC controller to score the workpiece according to the desired pattern. 
     In current automated systems, the breaking of the scored workpiece along the score lines is problematic. Often the process if performed manually, prior to moving the product to subsequent processing. The manual breaking of the scored workpiece is labor intensive and time-consuming. Additionally, none of the existing processes, such as thermal breaking, pressure wheels, templates or the like, for breaking the scored workpiece provide a consistently clean break or product edge. 
     An object of the present invention is to overcome the aforementioned difficulty with the prior art and to provide a process and apparatus for efficiently and accurately breaking scored workpieces, such as glass sheets, and transporting the resulting products. A further object of the present invention is to provide a process and apparatus for breaking scored workpieces which provides a consistent clean break or edge to the product. A further object of the present invention is to provide an automatic breaking process and apparatus which is both easy and economical to manufacture and to use and is easy to install in existing processing lines. 
     SUMMARY OF THE INVENTION 
     The above objects are achieved by a process for breaking scored sheets according to the present invention. The process includes at least the steps of floating a scored sheet on a fluid medium and impacting the scored sheet from above the floated scored sheet. A process for cutting glass sheets according to the present invention includes the steps of: scoring each glass sheet on an automatic scoring table having a movable scoring head; transporting each scored glass sheet to a breaking table; floating each scored sheet on a fluid medium on the breaking table; and impacting each scored sheet from above the floated scored sheet to fracture the scored sheet along the score lines. One modification of the present invention may provide that the scoring and breakout are performed at the same station. 
     One embodiment of the present invention includes scoring the workpiece on a scoring table and including vent lines within selected sections of the workpiece. The impact of the scored workpiece moves the impacted locations of the workpiece at least halfway into the floated air cushion in less than 0.25 seconds. Additionally, the impact may be performed by vacuum cups engaging the final product at a single or plurality of locations. Air cylinders may be used for controlling the vertical movement of the vacuum cups. After breaking, the vacuum cups may be used to transport the product in a conventional fashion. A single or plurality of flat pads may be used in place of the vacuum cups. The vacuum cups are useful for subsequent transporting of the workpiece. 
     An apparatus according to the present invention includes at least a workpiece receiving, or breaking, table with a mechanism for floating a workpiece thereon on a fluid medium, and a workpiece impacting mechanism. The apparatus for cutting glass sheets according to the present invention includes: a mechanism for scoring each glass sheet, such as an automatic scoring table having a movable scoring head; a breaking table adjacent the automatic cutting table; a mechanism for transporting each scored glass sheet to the breaking table; a mechanism for floating each scored sheet on a fluid medium on the breaking table; and a mechanism for impacting each scored sheet from above the floated scored sheet to fracture the scored sheet along the score lines. A separate loading table and a separate table with a separate cutter for cutting score lines and/or vent lines may also be incorporated into the system for faster processing. 
     In one embodiment of the present invention the receiving table provides an air cushion for floating the glass at least {fraction (3/16)} of an inch. The impacting mechanism may move the impacted locations of the workpiece at least halfway into the floated air cushion in less than 0.25 seconds, with the impact mechanism formed by vacuum cups which engage the product at a plurality of locations, and with air cylinders used for controlling the vertical movement of the vacuum cups. After breaking, the vacuum cups may be used to transport the product in a conventional fashion. 
     These and other advantages of the present invention will be clarified in the description of the preferred embodiments taken together with the attached drawings wherein like reference numerals represent like elements throughout. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 schematically illustrates an apparatus according to one embodiment of the present invention; 
     FIGS. 2 a - 2   d  schematically illustrate the process according to the present invention shown in FIG.  1 . 
     FIG. 3 schematically illustrates an air float table construction for the apparatus shown in FIG. 1; 
     FIG. 4 a  is a schematic plan view of an apparatus according to a second embodiment of the present invention; 
     FIG. 4 b  is a schematic plan view of a portion of the apparatus shown in FIG. 4 a;    
     FIG. 4 c  is a schematic plan view of an apparatus according to a third embodiment of the present invention; 
     FIG. 5 is an end view of a portion of the apparatus shown in FIGS. 4 a - 4   c.    
     FIGS. 6 a  and  6   b  illustrate movable pads of the apparatus shown in FIGS. 4 a - 4   c;    
     FIG. 7 is a plan view of an air float table of the apparatus in FIGS. 4 a - 4   c;  and 
     FIG. 8 schematically illustrates a glass workpiece configuration according to the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 schematically illustrates an apparatus for cutting frangible workpieces, particularly glass sheets  10 , also known as brackets in the automotive industry. However, the present invention is not limited to brackets or glass sheets  10  The apparatus includes a conventional automatic scoring table  12  which is also known as a glass cutting table. The scoring table  12  includes a movable scoring head  14 . The scoring head  14  is mounted for movement along a bridge  16  extending across the scoring table  12 . The bridge is mounted for movement along a track  18  extending the length of the scoring table  12 . In this manner, the scoring head  14 , the bridge  16  and the track  18  form an X-Y positioning system for moving the cutting element of the scoring head  14  across the sheet  10 . The movements of the cutting head  14  are controlled by a CNC controller (not shown) to automate the process. 
     The scoring table  12  additionally includes a conventional conveyor  20  shown schematically in FIG. 1 for moving the sheet  12  onto and off of the scoring table  12 . The conveyor  20  may be formed as a belt conveyor, as shown, or any conventional sheet conveying system. The scoring table  12  and the conveyor  20  are conventional elements known in the art and the specific construction of these elements does not form the details of the present invention. Examples of typical scoring tables are manufactured by Billco and others in the industry. Additionally, examples are found in U.S. Pat. No. 5,398,579 to Bando; U.S. Pat. No. 4,171,657 to Halberschmidt et al.; U.S. Pat. No. 4,709,483 to Hembree; U.S. Pat. No. 3,424,357 to Curtze et al.; U.S. Pat. No. 4,667,555 to Lisec and U.S. Pat. No. 3,151,794 to Brand, which are incorporated herein by reference. 
     A breaking table  22  is adjacent the scoring table  12  and is adapted to receive the sheet  10  therefrom by conveyor  20 . The breaking table  22  is formed as an air table and is adapted to float each scored sheet  10  on a fluid medium, particularly air, above the breaking table  22 . As schematically shown in FIG. 2 b,  the breaking table  22  includes a plurality of air ports  24  extending therethrough into an air channel  25  with the air ports  24  connected to a source (not shown) of pressurized fluid, particularly air. The air ports  24  may be ¼″ holes at 4″ to 6″ spacing. Vent channels  23  are provided between air channels  25 . Additionally, as shown in FIG. 3, the belt of conveyor  20  includes slots  29  therein to allow the air to flow through to support the sheet  10  on the belt. The vent channels  23  allow air to escape, either by an air pump or to atmosphere, such that the pressure is lower within vent channel  23  than between the belt of conveyor  20  and the sheet  10  such that the belt is held against the table top. The slots  29 , rather than holes, improve the airflow through the belt to further help the sheet  10  to be floated rather than the belt. 
     The breaking table  22  additionally includes a movable vacuum work holder  26 . The work holder  26  includes a series of vacuum chucks or cups  28  attached to an arm  30 . The vacuum cups  28  are spaced from each other and adapted to engage the sheet  10  as described below. The vacuum cups  28  are controlled in a conventional manner, as known in the art. The arm  30  is preferably movable in a conventional fashion for transportation of a sheet  10  attached to the vacuum cups  28 . The vacuum cups  28  are used to impact the scored sheet  10  which floats on the air cushion supplied by breaking table  22  to fracture the scored sheet along the score lines. Pneumatic cylinders  32  may be used to control the quick movement of the vacuum cups  28  and the arm  30  needs to quickly impact the glass sheet  10  to fracture the glass sheet  10  along the score lines. This will be further detailed in the following description of the process of cutting glass sheets  10  according to the present invention. 
     The process of cutting glass sheets  10  according to the present invention is schematically illustrated in FIGS. 2 a - 2   d.  FIG. 2 a  is a schematic plan view of a glass sheet  10  that has been scored on the scoring table  12 . The glass sheet  10  includes a score line  40  around the periphery of a final product  42  which may be, for illustrative example, a windshield. Additionally, the glass sheet  10  includes vent lines  44  extending from selected portions of the score lines  40  to the periphery of the glass sheet  10 . Each vent line  44  is also a score line, but unlike score line  40 , each vent line  44  is not along the periphery of the product  42 . During the breaking procedure, fractures through the glass sheet  10  propagate along the score line  40  and the vent lines  44 . The vent lines  44  are provided to ensure a clean break along the score line  40  and the edge of the final product  42 . Without the vent lines  44  at selected portions of the score line  40 , the break along the score line  40  may be irregular or even incomplete. The specific number of vent lines  44  will depend upon the shape of the final product  42 . However, with a conventional windshield shape, four vent lines  44  have been found to be sufficient. With regard to the positioning of the vent lines  44  during breakout, the cullet, or scrap pieces, each want to move outwardly away from the score line  40  in a straight line. The vent lines  44  are positioned to facilitate this straight line movement of each individual cullet piece. 
     Following the scoring of the glass sheet  10  as shown in FIG. 2 a,  the glass sheet is transported from the scoring table  12  to the breaking table  22  by conveyor  20 . Stops (not shown) may be provided on the breaking table  22  for proper positioning of the glass sheet  10 . Manual positioning or other known positioning methods may also be used. When the scored glass sheet  10  is received on the breaking table  22 , the glass sheet  10  is floated on a fluid medium, specifically, an air cushion, through air ports  24  in breaking table  22 , as shown in FIG. 2 b.  The height of the air cushion will depend on the size and grade of the glass sheet  10 . However, an air cushion of at least {fraction (3/16)} of an inch has been found to be sufficient for a single strength glass sheet  10 . The thicker the air cushion, the greater the amount of pressure needed from the air ports  24  and air channels  25 . 
     Following the floating of the scored glass sheet  10  on the breaking table  22  and in the proper position, the pneumatic cylinders  32  are activated to impact the vacuum cups  28  against the glass sheet  10  in a rapid single stroke. Specifically, the vacuum cups  28  engage the glass sheet  10  and force the glass sheet  10  rapidly down generally at least one-half of the thickness of the air cushion in less than about 0.25 seconds. This rapid impact causes a fracture to propagate through the glass sheet  10  along the score line  40  and vent lines  44  to complete the breaking process. During this impacting, the vacuum cups  28  engage and attach to the final product  42  in a conventional fashion. The separation of the final product  42  from the remaining sections of the glass sheet  10  is schematically illustrated in FIG. 2 d.  As shown in FIG. 2 d,  the vacuum cups  28  are positioned on the arm  30  to engage only the final product  42  at a plurality of spaced locations. The use of a plurality of vacuum cups  28  to impact the glass sheet  10  has the advantage of distributing the forces over the area of the vacuum cups  28 . Additionally, a single large vacuum cup may be used. 
     Following the breaking procedure, the final product  42  may be moved by arm  30  (as shown in phantom in FIG. 2 d ) to the next station for subsequent processing. After transportation of the final product  42 , the remaining cullet pieces or scrap can be removed from the breaking table  22  and the process repeated for another glass sheet  10 . The removal of the scrap from the breaking table  22  may be automated, such as a reciprocating sweep member (not shown), to guide the scrap to a recycle bin (not shown), or it may be manual. Additionally, the scoring table  12  may begin operation on the next glass sheet  10  as soon as the preceding glass sheet  10  is transported to the breaking table  22 . A single conveyor may be provided to run through the entire system. 
     The apparatus and process of the present invention provide for efficient and accurate breaking of the scored glass sheets  10 . Additionally, the present invention provides improved consistent breaks for the edge of the final product  42 , minimizing the subsequent processing of the final product  42 . The present system improves the speed of the current processes and automates subsequent transportation. The present invention is easy to operate, manufacture and install in existing processing lines. 
     FIGS. 4 a  and  4   b  schematically illustrate an apparatus for scoring and breaking out glass sheets  10  according to a second embodiment of the present invention. This system includes a loading station  50 , a cutting or scoring station  52  with controllable cutter  54  and a breakout station  56  with a plurality of vertically movable pads  58 . A wide slot type belt  60  extends through the loading station  50 , scoring station  52  and breaking station  56 . As shown in FIG. 4 b,  air cylinders  62  can control movement of the vertically movable pads  58  and a brush  64  can engage and clean the belt  60 . Additionally, the system includes a cullet bin  66  and a subsequent conveyor  68  which is spaced from the belt  60  over the cullet bin  66  by a distance less than the final product as discussed below. FIGS. 5-7 show details of the breakout station  56 . The pads  58  are attached to cylinders  62  which are secured to mounting bracket  70  for attachment to a frame  72  extending across the air float table  74  of breakout station  56 . The brackets  70  allow for easy adjustment of pads  58  along the frame  72 . FIG. 7 is a plan view of the air float table  74  showing the construction of air channels  25 , air vents  23  and air ports  24 . 
     In operation, the workpiece is loaded at the loading station  50  and moved to the scoring station  52  in which the appropriate score lines  40  and vents  44  will be placed on the glass sheet  10 . The scored glass sheet  10  is then moved to the breakout station  56  which is constructed as an air table as discussed above in connection with breaking table  22 . The vertically movable pads  58  are used to impact and break out the final product  42  in the same manner as vacuum cups  28  discussed above except that the pads  58  do not attach to the glass sheet  10  or final product  42 . After breakout, the belt  60  is activated moving the cullet into the cullet bin  66 . During this movement, the final product  42  will bridge the gap between the belt  60  and the conveyor  68  with the conveyor  68  transporting the final product to the subsequent processing. The movable pads  58  may be positioned to further prevent the final product from being directed towards the cullet bin  66 . The system illustrated in FIGS. 4 a  and  4   b  is intended to illustrate the apparatus of the present invention which does not require vacuum chucks for operation. The use of vacuum chucks is preferred if after impacting the glass, the vacuum chucks pick the lite out of the cullet. Such that the cullet is allowed to more effectively float away from the lite. With the vacuum chucks, the lite may then be transferred to some other location as discussed above or lowered back into its original location. FIG. 4 c  schematically illustrates a layout similar to FIG. 4 a  except for the inclusion of a vent cutting station  80  which would include its own controllable cutter  54 . The provision of a scoring station  52  and a vent cutting station  80  each with its own controllable cutter  54  is believed to improve the speed of the overall system. 
     In the absence of vent lines  44 , it is possible with appropriate scoring of the score line  40  to breakout an interior portion while remaining the entire exterior portion of the glass sheet intact. FIG. 8 schematically illustrates a glass sheet  10  with a score line  40  in which the outer portion remains intact after breakout and forms the final product  82  while the interior cullet  84  represents the scrap material. The interior cullet  84  may be removed by vacuum cups  28  or by falling into a cullet bin  66  in the manner described above. FIG. 8 is intended to illustrate the processing opportunities available with the system of the present invention. 
     The present invention is not intended to be limited by the specific examples discussed herein. Various modifications may be made to the present invention without departing from the spirit and scope thereof.