Patent Publication Number: US-2019169063-A1

Title: Apparatus and method for severing a glass sheet

Description:
This application is a continuation of U.S. application Ser. No. 15/101,122, filed on Jun. 2, 2016, which claims the benefit of priority under 35 U.S.C. § 371 of International Application No. PCT/US2014/067604, filed on Nov. 26, 2014, which claims the benefit of priority under 35 U.S.C. § 119 to U.S. Provisional Application No. 61/911,111, filed on Dec. 3, 2013, the content of each of which is relied upon and incorporated herein by reference in its entirety. 
    
    
     BACKGROUND 
     1. Field 
     This disclosure relates to glass sheets, and more particularly to an apparatus and method for severing a glass sheet. 
     2. Technical Background 
     A glass sheet may be formed using a variety of different processes. During or after formation, the glass sheet may be cut to a particular size and shape as part of forming a glass article from the cut glass sheet. 
     SUMMARY 
     In one embodiment, a method for severing a glass sheet comprises preferentially heating a region of the glass sheet to form a softened region. A slit is formed in the softened region of the glass sheet to form a slit region. The slit extends at least partially into a thickness of the glass sheet. Heat is preferentially applied to the slit region of the glass sheet. 
     In another embodiment, an apparatus comprises a first heating unit advanceable along a path on a glass sheet to form a softened region. The apparatus further comprises a shearing unit positioned adjacent to the first heating unit and advanceable along the path to form a slit in the softened region to form a slit region. The apparatus further comprises a second heating unit positioned adjacent to the shearing unit and advanceable along the path to apply heat to the slit region. 
     In another embodiment, a system comprises a laminated glass sheet comprising a core layer disposed between a first cladding layer and a second cladding layer. A first heating unit is configured to heat a region of the glass sheet preferentially to form a softened region. A shearing unit is configured to form a slit in the softened region. At least a portion of the first cladding layer is urged toward the second cladding layer. A second heating unit is configured to apply heat preferentially to the slit formed in the softened region. 
     Additional features and advantages will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the embodiments as described herein, including the detailed description which follows, the claims, as well as the appended drawings. 
     It is to be understood that both the foregoing general description and the following detailed description are merely exemplary, and are intended to provide an overview or framework to understanding the nature and character of the claims. The accompanying drawings are included to provide a further understanding, and are incorporated in and constitute a part of this specification. The drawings illustrate one or more embodiment(s), and together with the description serve to explain principles and operation of the various embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of one exemplary embodiment of an apparatus for severing a glass sheet. 
         FIG. 2  is a cross sectional view of one exemplary embodiment of a laminated glass sheet. 
         FIG. 3  is a cross sectional view of one exemplary embodiment of a laminate overflow distributor apparatus for producing a laminated glass sheet. 
         FIG. 4  is an elevation view of one exemplary embodiment of a shearing unit. 
         FIG. 5  is an elevation view of another exemplary embodiment of a shearing unit. 
         FIG. 6  is a close-up view of one exemplary embodiment of a tip configuration of a shearing unit. 
         FIG. 7  is a close-up view of another exemplary embodiment of a tip configuration of a shearing unit. 
         FIG. 8  is a close-up view of another exemplary embodiment of a tip configuration of a shearing unit. 
         FIG. 9  is an elevation view of another exemplary embodiment of an apparatus for severing a glass sheet. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to exemplary embodiments which are illustrated in the accompanying drawings. Whenever possible, the same reference numerals will be used throughout the drawings to refer to the same or like parts. The components in the drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the exemplary embodiments. 
       FIG. 1  shows one exemplary embodiment of an apparatus  100  for severing a glass sheet. The apparatus  100  comprises a first heating unit  120 , a shearing unit  140 , and a second heating unit  160 . In some embodiments, the first heating unit  120 , the shearing unit  140 , and the second heating unit  160  are structured and arranged to sever the glass sheet along a determined path extending along the glass sheet as further described below. The glass sheet can have any suitable configuration and can be formed using any suitable process (e.g., fusion-draw, down-draw, slot-draw, up-draw, or float). In some embodiments, the glass sheet is formed using a fusion-draw process, for example, as described below with reference to  FIGS. 2-3 . In any of the embodiments described herein, the glass sheet can be substantially planar (e.g., a flat glass sheet) or non-planar (e.g., a curved or formed glass sheet). 
       FIG. 2  is a cross sectional view of one exemplary embodiment of a laminated glass sheet  200 . The apparatus  100  can be used to sever a glass sheet such as, for example, the laminated glass sheet  200  as further described below. In some embodiments, the laminated glass sheet  200  comprises a core layer  202  disposed between a first cladding layer  204  and a second cladding layer  206 . The first cladding layer  204  and the second cladding layer  206  are exterior layers as shown in  FIG. 2 . The core layer  202  comprises a first major surface and a second major surface opposite the first major surface. In some embodiments, the first cladding layer  204  is fused to the first major surface of the core layer  202 . Additionally, or alternatively, the second cladding layer  206  is fused to the second major surface of the core layer  202 . In some of such embodiments, the interface between the first cladding layer  204  and the core layer  202  and/or between the second cladding layer  206  and the core layer  202  is free of any bonding material such as, for example, an adhesive, a coating layer, or any other material added or configured to adhere the respective cladding layer to the core layer. In this manner, one or both of the cladding layers  204  and  206  is fused directly to the core layer  202 . The first cladding layer  204  and the second cladding layer  206  are directly adjacent to the core layer  202 . 
     Although the laminated glass sheet  200  is shown as having three layers, other embodiments are included in this disclosure. In other embodiments, a laminated glass sheet can have any suitable number of layers, such as two, four, or more layers. In embodiments in which the laminated glass sheet has more than three layers, one or more intermediate layers are disposed between the core layer and one of the cladding layers. Thus, the cladding layers are exterior layers regardless of the total number of layers included in the laminated glass sheet. 
     In some embodiments, the laminated glass sheet  200  is configured as a strengthened glass sheet. In some embodiments, for example, the cladding layers  204  and  206  are formed from a glass composition having a different average coefficient of thermal expansion (CTE) than the core layer  202 . For example, in some of such embodiments, the cladding layers  204  and  206  are formed from a glass composition having a lower CTE than the core layer  202 . The mismatched CTE (i.e., the difference between the CTE of the cladding layers  204  and  206  and the CTE of the core layer  202 ) results in formation of compressive stress in the cladding layers and/or tensile stress in the core layer upon cooling of the laminated glass sheet  200 . In some embodiments, the tensile stress in the core layer  202  is, for example, at least about 30 MPa, at least about 65 MPa, or at least about 100 MPa. 
     Although the cladding layers  204  and  206  are described herein as being formed from the same glass composition and having a lower CTE than the core layer  202 , other embodiments are included in this disclosure. In other embodiments, the cladding layers can be formed from the same or different glass compositions, and each cladding layer, independently, can have a higher CTE or a lower CTE than the core layer. 
       FIG. 3  illustrates one exemplary embodiment of a laminate overflow distributor apparatus  300  that can be used to form a laminated glass sheet such as, for example, the laminated glass sheet  200 . The apparatus  300  is configured generally as described in U.S. Pat. No. 4,214,886, which is incorporated herein by reference in its entirety. The apparatus  300  comprises an upper overflow distributor  320  positioned above a lower overflow distributor  340 . The upper overflow distributor  320  comprises a trough  322 . A first glass composition  324  is melted and fed into the trough  322  in a viscous state. The first glass composition  324  forms the cladding layers  204  and  206  of the laminated glass sheet  200  as further described below. The lower overflow distributor  340  comprises a trough  342 . A second glass composition  344  is melted and fed into the trough  342  in a viscous state. The second glass composition  344  forms the core layer  202  of the laminated glass sheet  200  as further described below. 
     The second glass composition  344  overflows the trough  342  and flows down opposing outer forming surfaces  346  and  348  of the lower overflow distributor  340 . The outer forming surfaces  346  and  348  converge at a draw line  350 . The separate streams of the second glass composition  344  flowing down the respective outer forming surfaces  346  and  348  of the lower overflow distributor  340  converge at the draw line  350  where they are fused together to form the core layer  202  of the laminated glass sheet  200 . 
     The first glass composition  324  overflows the trough  322  and flows down opposing outer forming surfaces  326  and  328  of the upper overflow distributor  320 . The first glass composition  324  is deflected outward by the upper overflow distributor  320  such that the first glass composition flows around the lower overflow distributor  340  and contacts the second glass composition  344  flowing over the outer forming surfaces  346  and  348  of the lower overflow distributor. The separate streams of the first glass composition  324  are fused to the respective separate streams of the second glass composition  344  flowing down the respective outer forming surfaces  346  and  348  of the lower overflow distributor  340 . Upon convergence of the streams of the second glass composition  344  at the draw line  350 , the first glass composition  324  forms the cladding layers  204  and  206  of the laminated glass sheet  200 . 
     In some embodiments, the laminated glass sheet  200  is in the form of a glass ribbon traveling away from the draw line  350  of the lower overflow distributor  340  as shown in  FIG. 3 . The laminated glass sheet  200  cools as it travels away from the lower overflow distributor  340 . In some embodiments, the first glass composition  324  has a different CTE than the second glass composition  344  as described above such that, upon cooling of the laminated glass sheet  200 , compressive stress is created in the cladding layers  204  and  206  and tensile stress is created in the core layer  202 . In this manner, the laminated glass sheet  200  is configured as a strengthened glass sheet. 
     Returning to  FIG. 1 , in some embodiments, the laminated glass sheet  200  traveling away from the lower overflow distributor  340  comprises a bead extending along one or both of opposing side edges  210  and  212  thereof. The bead is a portion of the laminated glass sheet  200  having a greater thickness than a central portion of the laminated glass sheet. It may be desirable to separate the bead from the central portion of the laminated glass sheet  200  disposed between the side edges  210  and  212 . To that end, in some embodiments, the apparatus  100  is arranged to remove the bead from the side edge  210  of the laminated glass sheet as shown in  FIG. 1  and further described below. 
     The apparatus  100  is configured to sever the laminated glass sheet  200  along a path  220  extending along the laminated glass sheet. In some embodiments, the path  220  extends longitudinally along the length of the laminated glass sheet  200  adjacent to the side edge  210  as shown in  FIG. 1 . In some of such embodiments, the path  220  is substantially parallel to the side edge  210 . Severing the laminated glass sheet  200  along the path  220  can enable separation of the bead from the central portion of the laminated glass sheet. In other embodiments, the path can extend along the laminated glass sheet at any other location and in any other pattern. In this manner, the laminated glass sheet can be cut to any desired size and/or shape. 
     The first heating unit  120  is configured to selectively or preferentially heat a region of the laminated glass sheet  200  disposed along the path  220  to form a heated region. In some embodiments, the first heating unit  120  is configured to move relative to the laminated glass sheet  200  to advance along the path  220 . Such movement can be caused by maintaining the first heating unit  120  in a stationary position while moving the laminated glass sheet  200 , by maintaining the laminated glass sheet in a stationary position while moving the first heating unit, or by moving both the first heating unit and the laminated glass sheet. For example, in some embodiments, the first heating unit  120  remains stationary while the laminated glass sheet  200  moves relative to the first heating unit in a traveling direction  180  (e.g., away from the lower overflow distributor  340 ) as shown in  FIG. 1 . As the laminated glass sheet  200  moves relative to the first heating unit  120 , the first heating unit advances along the path  220 . The region of the laminated glass sheet  200  is heated progressively along the path  220  as the first heating unit  120  advances along the path. 
     In some embodiments, preferentially heating the region of the laminated glass sheet  200  comprises heating the region of the laminated glass sheet including the path  220  and portions of the laminated glass sheet a determined distance to either side of the path with the first heating unit  120  without substantially heating a remote region of the glass sheet disposed away from the path. In this manner, the heated region of the laminated glass sheet  200  has a predetermined width that is less than the width of the laminated glass sheet. In some embodiments, the predetermined width of the heated region is, for example, from about 1% to about 25% of the width of the laminated glass sheet, or from about 1% to about 10% of the width of the laminated glass sheet. In some embodiments, the width of the heated region depends on the temperature of the remote region of the glass sheet disposed away from the path. For example, in some of such embodiments, the width of the heated region is inversely proportional to the temperature of the remote region. In this manner, the heated region is wider when the temperature of the remote region is lower. This can aid in controlling the temperature gradient between the remote region and the heated region to avoid breaking the glass sheet. The heated region has a shape corresponding to the shape of the path  220 . For example, in some embodiments, the heated region is a substantially straight line extending longitudinally along the length of the laminated glass sheet as shown in  FIG. 1 . In other embodiments, the heated region is curved as further described below with reference to  FIG. 9 . 
     In some embodiments, the first heating unit  120  is configured to heat the region of the laminated glass sheet  200  to at least a softening temperature of the laminated glass sheet. In this manner, the heated region comprises a softened region. The softening temperature is a temperature at which a small diameter fiber of a glass composition will elongate under its own weight. One suitable method for determining the softening temperature is that described in ASTM C338. In some embodiments, the softening temperature of the laminated glass sheet  200  is the higher of the softening temperature of the glass composition of the core layer  202  and the softening temperature of the glass composition of the cladding layers  204  and  206 . In some embodiments, the heated region of the laminated glass sheet  200  is maintained at or above the softening temperature. This can aid in severing the laminated glass sheet with the shearing unit  140  and/or the second heating unit  160  as further described below. 
     In some embodiments, the first heating unit  120  is configured to heat the region of the laminated glass sheet  200  in a substantially uniform manner across the thickness of the laminated glass sheet. In this manner, the temperature gradient across the thickness of the laminated glass sheet  200  is minimized. This can aid in avoiding the formation of stress across the thickness of the laminated glass sheet  200 , which can cause the laminated glass sheet to break (e.g., due to the stress formed therein) as opposed to being sheared by the shearing unit as further described below. Breaking, as opposed to shearing, the laminated glass sheet  200  can cause the core layer  202  to be exposed (e.g., because the cladding layers  204  and  206  may not be wrapped around the core layer at the broken edge). 
     In some embodiments, the laminated glass sheet  200  is heated to a temperature ranging from the softening temperature to an upper temperature limit. The upper temperature limit ranges, for example, from about 100% to about 110% of the softening temperature. In some embodiments, the upper temperature limit depends on the slope of the viscosity curve (i.e., a plot of temperature vs. viscosity) of the glass composition (e.g., the glass composition of the core layer  202  and/or the glass composition of the cladding layers  204  and  206 ) between the annealing temperature and the softening temperature. For example, in some embodiments, the upper temperature limit is proportional to the average slope of the viscosity curve of the glass composition between the annealing temperature and the softening temperature. If the region is heated to a temperature below the softening temperature, the glass sheet  200  may break as opposed to being sheared upon engagement by the shearing unit  140  as described below. If the region is heated to a temperature above the upper temperature limit, the cladding layers  204  and  206  may not be sufficiently rigid to be urged together to envelope the core layer  202  as described below. In other words, the cladding layers  204  and  206  may be too soft to be wrapped around the core layer  202 . 
     Upon being heated to at least the softening temperature, the heated region of the laminated glass sheet  200  is sufficiently malleable to be sheared as further described below. In some embodiments, upon heating the region of the laminated glass sheet  200  to at least the softening temperature, the remote region of the laminated glass sheet disposed away from the path remains below the softening temperature of the laminated glass sheet. In some embodiments, upon heating the region of the laminated glass sheet  200  to at least the softening temperature, the remote region of the laminated glass sheet disposed away from the path remains below an annealing temperature of the laminated glass sheet. Alternatively, in other embodiments, the temperature of the remote region of the laminated glass sheet is above the annealing temperature upon heating the region of the laminated glass sheet to at least the softening temperature. 
     The first heating unit  120  can be configured as any type of heating unit capable of raising the temperature of at least a portion of the laminated glass sheet  200  to at least the softening temperature. For example, the first heating unit  120  can comprise a torch, an infrared heater, an induction heater, a resistance heater, a radiant heater, a laser, or any other suitable heating member. In some embodiments, the first heating unit  120  is positioned adjacent to a first outer surface  214  and/or a second outer surface  216  of the laminated glass sheet  200 . For example, in some embodiments, the first heating unit  120  comprises two heating members positioned adjacent to opposing outer surfaces  214  and  216  of the laminated glass sheet as shown in  FIG. 1 . In this manner, the laminated glass sheet  200  passes between the opposing heating members of the first heating unit  120 . This may enable uniform heating of the region of the laminated glass sheet  200  (e.g., by heating the laminated glass sheet from both outer surfaces). 
     The shearing unit  140  is configured to form a slit in the heated region or softened region of the laminated glass sheet  200  disposed along the path  220  to form a slit region. In some embodiments, the shearing unit  140  is configured to move relative to the laminated glass sheet  200  to advance along the path  220 . Such movement can be caused by maintaining the shearing unit  140  in a stationary position while moving the laminated glass sheet  200 , by maintaining the laminated glass sheet in a stationary position while moving the shearing unit, or by moving both the shearing unit and the laminated glass sheet. In some embodiments, the shearing unit  140  remains stationary while the laminated glass sheet  200  moves relative to the shearing unit in the traveling direction  180  as shown in  FIG. 1 . As the laminated glass sheet  200  moves relative to the shearing unit  140 , the shearing unit advances along the path  220 . The heated region of the laminated glass sheet  200  is slit progressively along the path  220  as the shearing unit  140  advances along the path. 
     In some embodiments, the shearing unit  140  is configured to at least partially sever the first cladding layer  204  and urge an edge of the severed first cladding layer toward the second cladding layer  206 . Additionally, or alternatively, the shearing unit  140  is configured to at least partially sever the second cladding layer  206  and urge an edge of the severed second cladding layer toward the first cladding layer  204 . By urging the cladding layers  204  and  206  together, the shearing unit can aid in wrapping the cladding layers around the core layer at the slit. This can aid in preventing the core layer  202  from being exposed at a severed edge of a glass article after the laminated glass sheet  200  is severed to form the glass article. In other words, this can aid in providing a glass article in which the core layer  200  is substantially entirely enveloped within a shell formed by the cladding layers  204  and  206 . In some embodiments, because the core layer  202  is under tension, exposure of the core layer can result in fracture of the laminated glass sheet  200 . Therefore, ensuring that the core layer  202  is enveloped within the shell formed by the cladding layers  204  and  206  can aid in producing a more robust glass article. 
     In some embodiments, the shearing unit  140  comprises a first shearing member  142  and a second shearing member  144  as shown in  FIG. 1 . In some of such embodiments, the first shearing member  142  is positioned adjacent to the first outer surface  214  of the laminated glass sheet  200 . Additionally, or alternatively, the second shearing member  144  is positioned adjacent to the second outer surface  216  of the laminated glass sheet  200 . In this manner, the laminated glass sheet  200  passes between the shearing members  142  and  144 . In some embodiments, the distance between the shearing members  142  and  144  is adjustable to accommodate glass sheets having different thicknesses. 
       FIG. 4  illustrates one exemplary embodiment of the shearing unit  140 . The first shearing member  142  is configured as a rotating disc. To that end, the first shearing member  142  comprises a shaft portion  145  and a disc portion  146 . In some embodiments, the disc portion  146  is rotatable relative to the shaft portion  145 . In some of such embodiments, the disc portion  146  is freely rotatable relative to the shaft portion  145  (e.g., due to movement of the laminated glass sheet  200  relative to the shearing member  140 ). Alternatively, in other embodiments, the disc portion  146  is driven (e.g., by an electric motor) to rotate relative to the shaft portion  145 . The second shearing member  144  is configured as a rotating disc. To that end, the second shearing member  144  comprises a shaft portion  147  and a disc portion  148 . In some embodiments, the disc portion  148  is rotatable relative to the shaft portion  147 . The disc portion  148  can rotate freely relative to the shaft portion  147  or can be driven to rotate relative to the shaft portion. 
     In some embodiments, the first shearing member  142  comprises a shearing tip region  151  and/or the second shearing member  144  comprises a shearing tip region  152 . The shearing tip regions  151  and  152  extend circumferentially around the respective disc portion  146  and  148  of the respective shearing member  142  and  144 . In this manner, the peripheries of the disc portions  146  and  148  are configured as shearing tips. The shearing tip regions  151  and  152  are configured to cut into the heated region of the laminated glass sheet  200  to form the slit therein. For example, in some embodiments, the shearing tip region  151  of the first shearing member  142  cuts into the first cladding layer  204  of the laminated glass sheet  200  from the first surface  214 . Additionally, or alternatively, the shearing tip region  152  of the second shearing member  144  cuts into the second cladding layer  206  of the laminated glass sheet  200  from the second surface  216 . In some embodiments, the shearing tip regions  151  and  152  can be blunted. This can aid in pulling the cladding layers  204  and  206  toward one another as the shearing tip regions  151  and  152  cut into the laminated glass sheet  200 . Alternatively, in other embodiments, the shearing tip regions can be sharpened. This can aid in precisely slicing into the laminated glass sheet  200 , but may be less effective at pulling the cladding layers  204  and  206  toward one another to wrap the cladding layers around the core layer  202 . 
     In some embodiments, the shearing members  142  and  144  are positioned relative to one another such that the shearing tip regions  151  and  152  are offset. For example, in some of such embodiments, the shearing tip regions  151  and  152  are offset in the traveling direction  180  as shown in  FIG. 4 . In this manner, the first shearing member  142  and the second shearing member  144  cut into the laminated glass sheet  200  at different transverse positions along the width of the laminated glass sheet. This can aid in enveloping the core layer  202  within the shell formed by the cladding layers  204  and  206 . For example, if the shearing tip regions of the shearing members were aligned in the traveling direction, the shearing unit may form a straight cut through the laminated glass sheet, leaving the core layer exposed at the severed edge. However, the offset shearing tip regions  151  and  152  of the shearing members  142  and  144  cause the severed edges of the cladding layers  204  and  206  to move toward one another to wrap the cladding layers around the core layer  202  as shown in  FIG. 4 . In some embodiments, end portions of the cladding layers  204  and  206  near the severed edge are thinned as the cladding layers are pulled around the core layer  202 . In other words, the cladding layers  204  and  206  are stretched while being pulled around the core layer such that the thickness of the end portions of the cladding layers is reduced. In this manner, the shell formed by the cladding layers  204  and  206  comprises an end portion that is adjacent to the severed edge of the laminated glass sheet  200  and thinner than the remainder of the shell spaced away from the severed edge as shown in  FIG. 4 . 
       FIG. 5  shows another exemplary embodiment of the shearing members  142  and  144 . In some embodiments, the first shearing member  142  comprises a contoured region  153  positioned adjacent to the shearing tip region  151 . Additionally, or alternatively, the second shearing member  144  comprises a contoured region  154  positioned adjacent to the shearing tip region  152 . The contoured regions  153  and  154  are positioned opposite one another and configured to shape the severed edge of the laminated glass sheet  200 . For example, the contoured regions  153  and  154  shown in  FIG. 5  are configured as substantially straight tapered regions. The contoured regions  153  and  154  are tapered in opposite directions such that the space between the contoured regions has a substantially triangular shape. Upon passage of the laminated glass sheet  200  between the shearing members, the severed edge of the laminated glass sheet takes on a beveled shape corresponding to the shapes of the contoured regions  153  and  154  of the shearing members  142  and  144 . In some embodiments, the shell formed by the cladding layers  204  and  206  comprises a thinned end portion as described above with reference to  FIG. 4 . 
     The contoured regions can have any suitable shape configured to form a desired shape at the severed edge of the laminated glass sheet. For example,  FIG. 6  shows one exemplary embodiment of shearing members having contoured regions  153   a  and  154   a . Each of the contoured regions  153   a  and  154   a  comprises a curved taper. The contoured regions  153   a  and  154   a  are curved in opposite directions such that the space between the contoured regions has a substantially semi-elliptical shape. Upon passage of the laminated glass sheet  200  between the shearing members, the severed edge of the laminated glass sheet takes on a semi-elliptical shape corresponding to the shapes of the contoured regions  153   a  and  154   a . In this manner, the severed edge of the laminated glass sheet  200  is given a rounded or bullnose shape. In some embodiments, the shell formed by the cladding layers  204  and  206  comprises a thinned end portion as described above with reference to  FIG. 4 . 
       FIG. 7  shows one exemplary embodiment of shearing members having contoured regions  153   b  and  154   b . Each of the contoured regions  153   b  and  154   b  comprises a tapered portion and a flat portion adjacent to the tapered portion. Upon passage of the laminated glass sheet  200  between the shearing members, the severed edge of the laminated glass sheet takes on a beveled shape corresponding to the shapes of the contoured regions  153   b  and  154   b . In some embodiments, the bevel formed by the contoured regions  153   b  and  154   b  shown in  FIG. 7  is somewhat steeper than the bevel formed by the contoured regions  153  and  154  shown in  FIG. 5 . In some embodiments, such a steeper taper as shown in  FIG. 7  is suitable for use with a relatively thin laminated glass sheet (e.g., a laminated glass sheet having a thickness of at most about 1 mm). In some embodiments, the shell formed by the cladding layers  204  and  206  comprises a thinned end portion as described above with reference to  FIG. 4 . 
       FIG. 8  shows one exemplary embodiment of shearing members having contoured regions  153   c  and  154   c . The contoured region  153   c  comprises a curved taper. The contoured region  154   c  comprises a tapered notch. The curved taper is configured to fit within the tapered notch as shown in  FIG. 8 . Upon passage of the laminated glass sheet  200  between the shearing members, the severed edge of the laminated glass sheet comprises a lip corresponding to the shape of the space between the contoured regions  153   c  and  154   c . In some embodiments, the shell formed by the cladding layers  204  and  206  comprises a thinned end portion as described above with reference to  FIG. 4 . 
     In some embodiments, the shearing unit  140  severs each of the first cladding layer  204 , the second cladding layer  206 , and the core layer  202 . In this manner, the slit formed in the laminated glass sheet  200  extends entirely through the thickness of the laminated glass sheet (e.g., as shown in  FIG. 4 ). In other words, the laminated glass sheet  200  is severed by the shearing unit  140 . Alternatively, in other embodiments, the slit formed in the laminated glass sheet  200  extends through only a portion of the thickness of the laminated glass sheet (e.g., as shown in  FIG. 5 ). In some of such embodiments, upon forming the slit in the laminated glass sheet  200 , the shearing unit  140  leaves one or more of the first cladding layer  204 , the second cladding layer  206 , or the core layer  202  at least partially unsevered. A first portion of the laminated glass sheet  200  is positioned on a first side of the slit. A second portion of the laminated glass sheet  200  is positioned on a second side of the slit opposite the first portion. In some embodiments, upon formation of the slit in the laminated glass sheet  200 , the first portion of the laminated glass sheet and the second portion of the laminated glass sheet remain attached to one another by a membrane of glass material. The membrane of glass material is thinner than the laminated glass sheet  200 . In other words, the shearing unit  140  partially severs the laminated glass sheet  200  such that the slit does not extend entirely through the thickness of the laminated glass sheet. In this manner, the slit region of the laminated glass sheet  200  is a thinned region having a reduced thickness relative to the remainder of the laminated glass sheet. The membrane can comprise at least a portion of the first cladding layer  204 , the second cladding layer  206 , and/or the core layer  202 . In some embodiments, the membrane is severed (e.g., by the second heating unit  160 ) to sever the glass sheet as further described below. 
     In some embodiments, upon formation of the slit in the laminated glass sheet  200 , the cladding layers  204  and  206  move toward one another as described above. The first cladding layer  204  is brought into close proximity to the second cladding layer  206  (e.g., at an edge of the slit) during formation of the slit. Additionally, or alternatively, the second cladding layer  206  is brought into close proximity to the first cladding layer  204  (e.g., at an edge of the slit) during formation of the slit. In some embodiments, the laminated glass sheet  200  is squeezed between the shearing members  142  and  144  such that the cladding layers  204  and  206  move around the core layer  202  and toward one another. In some embodiments, the first cladding layer  204  and the second cladding layer  206  move into contact with one another during formation of the slit in the laminated glass sheet  200 . The cladding layers  204  and  206  can be brought into contact with one another regardless of whether the portions of the laminated glass sheet  200  disposed on opposing sides of the slit remain attached to one another by the membrane after formation of the slit. In other words, the cladding layers  204  and  206  can be brought into contact with one another regardless of whether the laminated glass sheet  200  is severed during formation of the slit. 
     Although the shearing unit  140  has been described above as comprising two shearing members configured as rotating discs, other embodiments are included within this disclosure. In other embodiments, the shearing unit can comprise any number of shearing members (e.g., one, three, or more) having any suitable configuration. For example, in some embodiments, the shearing members are configured as one or more blades or tines positioned to contact the laminated glass sheet  200 . In some of such embodiments, the blades or tines are configured as elongate members positioned to engage the laminated glass sheet. The blades or tines comprise shearing tip regions and/or contoured regions as described above. The shearing tip regions of the blades or tines are offset relative to one another also as described above. 
     Returning to  FIG. 1 , the second heating unit  160  is configured to selectively or preferentially apply heat to the slit region of the laminated glass sheet  200  disposed along the path  220 . In some embodiments, the second heating unit  160  is configured to move relative to the laminated glass sheet  200  to advance along the path  220 . Such movement can be caused by maintaining the second heating unit  160  in a stationary position while moving the laminated glass sheet  200 , by maintaining the laminated glass sheet in a stationary position while moving the second heating unit, or by moving both the second heating unit and the laminated glass sheet. In some embodiments, the second heating unit  160  remains stationary while the laminated glass sheet  200  moves relative to the second heating unit in the traveling direction  180  as shown in  FIG. 1 . As the laminated glass sheet  200  moves relative to the second heating unit  160 , the second heating unit advances along the path  220 . Heat is progressively applied to the slit formed in the laminated glass sheet  200  as the second heating unit  160  advances along the path  220 . 
     In some embodiments in which the laminated glass sheet  200  is not severed upon formation of the slit as described above, application of heat to the slit region severs the laminated glass sheet. For example, in some embodiments, application of heat to the slit region severs the membrane of glass material extending between the first and second portions of the laminated glass sheet  200  to sever the laminated glass sheet. 
     Upon severing the laminated glass sheet  200  (e.g., by the shearing unit  140  or the second heating unit  160 ), the laminated glass sheet comprises a severed edge. In some embodiments, the second heating unit  160  applies heat to the severed edge of the laminated glass sheet  200 . This can aid in polishing the severed edge of the laminated glass sheet  200  and/or repairing defects in the severed edge of the laminated glass sheet that may have been formed during the severing process. To that end, in some embodiments, the second heating unit  160  comprises a torch configured to expose the severed edge of the laminated glass sheet  200  to a flame. In this manner, the second heating unit  160  flame polishes the severed edge of the laminated glass sheet  200 . This can aid in smoothing the severed edge and/or repairing cracks or other defects that may have been formed upon severing the laminated glass sheet  200 . This also can aid in securely fusing the cladding layers  204  and  206  to one another so that the core layer  202  remains unexposed at the severed edge of the laminated glass sheet  200 . 
     The second heating unit  160  can be configured as any type of heating unit capable of heating the laminated glass sheet  200 . For example, the second heating unit  160  can comprise any suitable heating member as described above with reference to the first heating unit  120 . In some embodiments, the second heating unit  160  is positioned adjacent to the first outer surface  214  and/or the second outer surface  216  of the laminated glass sheet  200 . For example, in some embodiments, the second heating unit  160  comprises two heating members positioned adjacent to opposing outer surfaces  214  and  216  of the laminated glass sheet as shown in  FIG. 1 . In this manner, the laminated glass sheet  200  passes between the opposing heating members of the second heating unit  160 . This can enable heat to be applied uniformly to the slit region of the laminated glass sheet  200  (e.g., by heating from both outer surfaces). 
     In some embodiments, the first heating unit  120 , the shearing unit  140 , and the second heating unit  160  are aligned with one another in the traveling direction  180  as shown in  FIG. 1 . The first heating unit  120 , the shearing unit  140 , and the second heating unit  160  are aligned with the path  220  extending longitudinally along the length of the laminated glass sheet  200  adjacent to the side edge  210 . In some embodiments, the first heating unit  120 , the shearing unit  140 , and the second heating unit  160  are maintained in a fixed position relative to the apparatus used to form the laminated glass sheet  200  (e.g., the laminate overflow distributor apparatus  300 ). For example, in some embodiments, the first heating unit  120 , the shearing unit  140 , and the second heating unit  160  are mounted on a frame or support structure to maintain the positions thereof. The laminated glass sheet  200  is moved in the traveling direction  180  relative to the apparatus  100 . In this manner, the first heating unit  120 , the shearing unit  140 , and the second heating unit  160  are sequentially advanced along the path  220  to sever the laminated glass sheet progressively along the path. In some embodiments, this enables the bead extending along the side edge  210  to be separated from the laminated glass sheet  200 . The laminated glass sheet  200  is severed and/or the bead is separated in a continuous manner (e.g., as the laminated glass sheet travels away from the lower overflow distributor  340 ). 
     In some embodiments, the laminated glass sheet  200  cools while traveling away from the overflow distributor apparatus  300  as described above. In some embodiments, the apparatus  100  is positioned a sufficient distance downstream of the overflow distributor apparatus  300  that the region of the laminated glass sheet  200  is below the softening temperature of the laminated glass sheet prior to being reheated by the first heating unit  120 . In this manner, the laminated glass sheet  200  is allowed to set prior to engagement by the apparatus  100 . In this manner, the remote region of the laminated glass sheet  200  is at least somewhat rigid and/or brittle upon severing the region of the laminated glass sheet. The stability provided by the remote region of the laminated glass sheet  200  can aid in precisely severing the laminated glass sheet at the region engaged by the apparatus  100  as described herein. 
     Although the apparatus  100  has been described in connection with severing the laminated glass sheet  200 , other embodiments are included in this disclosure. The apparatus  100  can be used to sever any type of glass sheet. The glass sheet can be laminated or non-laminated. In other words, the glass sheet can include a single layer of glass or multiple layers of glass. The glass sheet can be formed using any suitable process (e.g., fusion-draw, down-draw, slot-draw, up-draw, or float). The glass sheet can be strengthened or non-strengthened. The glass sheet can be strengthened in any suitable manner (e.g., CTE mismatch or ion exchange). 
     In some embodiments, a second apparatus  100   a  is positioned along a second path  220   a  adjacent to the side edge  212  of the laminated glass sheet  200  as shown in  FIG. 1 . The second apparatus  100   a  is configured generally as described above with reference to the apparatus  100 . For example, in some embodiments, the second apparatus comprises a first heating unit  120   a , a shearing unit  140   a , and a second heating unit  160   a . The second apparatus  100   a  is configured to sever the laminated glass sheet  200  to separate the bead from the side edge  212 . In some embodiments, both the first apparatus  100  and the second apparatus  100   a  are employed to remove the beads from both edges of the laminated glass sheet  200  to leave the central portion free of the beads. In this manner, the beads are removed continuously during production of the laminated glass sheet  200 . 
     In some embodiments, a third apparatus  100   b  is positioned adjacent to the laminated glass sheet  200  downstream of the apparatus  100  and/or the second apparatus  100   a  as shown in  FIG. 1 . The third apparatus  100   b  is similar to the apparatus  100 . For example, in some embodiments, the third apparatus comprises a first heating unit  120   b , a shearing unit  140   b , and a second heating unit  160   b . Each of the first heating unit  120   b , the shearing unit  140   b , and the second heating unit  160   b  extends along the width of the laminated glass sheet  200 . In some embodiments, the third apparatus  100   b  is configured to sever the laminated glass sheet  200  along a path that is substantially perpendicular to the path  220 . In other embodiments, the third apparatus  100   b  can be configured to sever the laminated glass sheet along a path that is disposed at any angle relative to the path  220 . 
     The first heating unit  120   b  is configured to selectively or preferentially heat a region of the laminated glass sheet  200  disposed along the path to form a heated region. In some embodiments, the first heating unit  120   b  extends transversely along substantially the entire width of the central portion of the laminated glass sheet  200 . For example, the first heating unit  120   b  extends along substantially the entire width between the path  220  and the path  220   a . In some embodiments, the first heating unit  120   b  comprises a bank of torches extending along the width of the laminated glass sheet  200 . 
     The shearing unit  140   b  is configured to form a slit in the heated region or softened region of the laminated glass sheet  200  disposed along the path to form a slit region. In some embodiments, the shearing unit  140   b  comprises a pair of shearing members as described above with reference to the shearing unit  140 . In some of such embodiments, the shearing members are configured to advance along the width of the laminated glass sheet  200  to form the slit in the heated region. For example, in some embodiments, the shearing members are configured to advance in a direction substantially perpendicular to the traveling direction  180  to form the slit in the heated region. In other embodiments, the shearing unit  140   b  comprises a pair of shearing members each extending transversely along substantially the entire width of the central portion of the laminated glass sheet  200 . In some of such embodiments, the shearing members are positioned adjacent to opposing surfaces of the laminated glass sheet  200  with the laminated glass sheet positioned between the shearing members. In some embodiments, each shearing member is configured as an elongate blade having a shearing tip region facing the laminated glass sheet  200 . Additionally, or alternatively, each shearing member comprises a contoured region adjacent to the shearing tip region. The shearing members are movable between a retracted position in which the shearing members are disengaged from the laminated glass sheet  200  and an advanced position in which the shearing members are engaged with the laminated glass sheet. In this manner, the shearing members are movable toward one another to engage the laminated glass sheet  200  and form the slit in the heated region. 
     The second heating unit  160   b  is configured to selectively or preferentially apply heat to the slit region of the laminated glass sheet  200  disposed along the path. In some embodiments, the second heating unit  160   b  extends transversely along substantially the entire width of the central portion of the laminated glass sheet  200 . For example, the second heating unit  160   b  extends along substantially the entire width between the path  220  and the path  220   a . In some embodiments, the second heating unit  160   b  is configured as a bank of torches extending along the width of the laminated glass sheet  200 . 
     In some embodiments, the laminated glass sheet  200  is configured as a glass ribbon traveling away from the lower overflow distributor  340  as described above. In some of such embodiments, the third apparatus  100   b  is configured to travel with the laminated glass sheet  200  to sever the laminated glass sheet along the path. For example, the apparatus  100   b  is positioned such that the first heating unit  120   b  is aligned with the path. The apparatus  100   b  travels with the ribbon to maintain the first heating unit  120   b  in alignment with the path until the region of the laminated glass sheet  200  is heated to at least the softening temperature. The position of the apparatus  100   b  is adjusted to align the shearing unit  140   b  with the heated region extending along the path of the laminated glass sheet  200 . The apparatus  100   b  travels with the ribbon to maintain the shearing unit  140   b  in alignment with the path until the slit is formed in the heated region of the laminated glass sheet  200 . In some embodiments, the slit is formed by advancing the shearing members along the width of the laminated glass sheet  200 . In other embodiments, the slit is formed by moving the shearing members toward one another to engage the laminated glass sheet positioned therebetween. The position of the apparatus  100   b  is adjusted to align the second heating unit  160   b  with the slit region extending along the path of the laminated glass sheet  200 . The apparatus  100   b  travels with the ribbon to maintain the second heating unit  160   b  in alignment with the path until sufficient heat has been applied to the slit region of the laminated glass sheet  200  to sever the laminated glass sheet and/or to polish the severed edge of the laminated glass sheet. In some embodiments, the position of the apparatus  100   b  is readjusted such that the first heating unit  120   b  is aligned with another path, and the process is repeated to sever the laminated glass sheet  200  along the other path. 
     In some embodiments, the use of the apparatus  100 , the second apparatus  100   a , and the third apparatus  100   b  in combination enables the laminated glass sheet  200 , which can be configured as a moving glass ribbon, to be cut to a desired size and shape (e.g., a rectangular shape). In some embodiments, the cladding layers  204  and  206  of the laminated glass sheet  200  are wrapped over the core layer  202  at each of the severed edges. In this manner, the core layer  202  is enveloped within the shell formed by the cladding layers  204  and  206 . 
       FIG. 9  shows one exemplary embodiment of an apparatus  400  for severing a glass sheet  500 . The glass sheet  500  can be laminated or non-laminated and strengthened or non-strengthened as described above. The apparatus  400  is configured to sever the glass sheet  500  along a path  520  extending along the glass sheet. In some embodiments, the path  520  extends along the glass sheet  500  to form a closed loop as shown in  FIG. 9 . Severing the glass sheet  500  along the path  520  enables a glass article having the shape of the closed loop to be cut from the glass sheet. In some embodiments, the glass article can be in the shape of an automobile window as shown in  FIG. 9 . In other embodiments, the path can extend along the laminated glass sheet in any other pattern to form a glass article having any desired shape. 
     In some embodiments, the apparatus  400  is similar to the apparatus  100  described above. For example, in some embodiments, the apparatus  400  comprises a first heating unit  420 , a shearing unit  440 , and a second heating unit  460 . The first heating unit  420  is configured to selectively or preferentially heat a region of the glass sheet  500  disposed along the path  520  to form a heated region. The shearing unit  440  is configured to form a slit in the heated region or softened region of the glass sheet  500  disposed along the path  520  to form a slit region. The second heating unit  460  is configured to selectively or preferentially apply heat to the slit region of the glass sheet  500  disposed along the path  520 . 
     In some embodiments, the first heating unit  420 , the shearing unit  440 , and the second heating unit  460  are sequentially advanced along the path  520  by relative movement between the apparatus  400  and the glass sheet  500 . For example, in some embodiments, the glass sheet  500  is held stationary, and the apparatus  400  is moved relative to the glass sheet. In some embodiments, the first heating unit  420 , the shearing unit  440 , and the second heating unit  460  are coupled to one another. For example, in some of such embodiments, the first heating unit  420 , the shearing unit  440 , and the second heating unit  460  are mounted on a support structure configured to move relative to the glass sheet  500 . In this manner, the apparatus  400  is configured to move as a unit along the path  520 . In some embodiments, the first heating unit  420 , the shearing unit  440 , and the second heating unit  460  are aligned with one another in a traveling direction  480 . In this manner, the first heating unit  420 , the shearing unit  440 , and the second heating unit  460  are advanced along the path  520  in succession to sever the glass sheet  500 . The traveling direction can be changed as the apparatus  400  is moved to maintain the apparatus in alignment with the path  520 . In some embodiments, movement of the apparatus  400  is automated. For example, in some of such embodiments, movement of the apparatus  400  is controlled by a computer numerical control (CNC) machine. 
     In some embodiments, the path  520  comprises one or more curved portions as shown in  FIG. 9 . The first heating unit  420 , the shearing unit  440 , and/or the second heating unit  460  are configured to follow the path  520  along curved portions thereof. For example, in some embodiments, the first heating unit  420  is articulated to enable the first heating unit to conform to the curvature of the path  520  as shown in  FIG. 9 . In other words, the first heating unit  420  is configured to bend or flex to conform to the curvature of the path  520 . In some embodiments, the shearing unit  440  and/or the second heating unit  460  is articulated in a similar manner to conform to the curvature of the path  520 . 
     The apparatuses and method described herein for severing a glass sheet may be beneficial for severing a laminated and/or strengthened glass sheet. Severing such a laminated or strengthened glass sheet using a conventional scoring and bending process may result in breakage of the glass sheet, especially if the glass sheet comprises a core layer with a relatively high tensile stress. Use of conventional scoring and bending processes to sever a laminated glass sheet can leave the core layer exposed at the severed edge, which can reduce the strength or resilience of the glass sheet. In some embodiments, the apparatuses and methods described herein enable severing of a laminated and/or strengthened glass sheet without breakage and without exposing the core layer at the severed edge of the glass sheet. This may enable production of a severed glass sheet that is capable of withstanding exposure to additional processing (e.g., molding into a glass article) and/or handling (e.g., during assembly of a display device including the severed glass sheet) without breaking. The apparatuses and methods described herein can be used to sever a glass sheet online (e.g., during production of the glass sheet) or offline (e.g., as a post-processing step after production of the glass sheet). For example, the apparatuses and methods described herein can be used to sever a hot glass sheet (e.g., at or near the discharge of a laminate overflow distribution apparatus) or a cold glass sheet (e.g., at or near room temperature). 
     It will be apparent to those skilled in the art that various modifications and variations can be made without departing from the spirit or scope of the invention. Accordingly, the invention is not to be restricted except in light of the attached claims and their equivalents.