Apparatus and method for severing a glass sheet

1. A method for severing a strengthened glass sheet comprising a glass core layer disposed between a first glass cladding layer and a second glass cladding layer, each of the first glass cladding layer and the second glass cladding layer comprising a lower coefficient of thermal expansion than the glass core layer such that the glass core layer comprises a tensile stress, the method comprising:

preferentially heating a region of the glass sheet to at least a softening temperature of the glass sheet to form a softened region, wherein a remote region of the glass sheet disposed away from the region remains below an annealing temperature of the glass sheet during the preferentially heating;

forming a slit in the softened region of the glass sheet to form a slit region, the slit extending at least partially into a thickness of the glass sheet; and

preferentially applying heat to the slit region of the glass sheet.

2. The method of claim 1 , wherein the preferentially applying heat to the slit region comprises applying heat sufficient to sever the glass sheet into first and second portions.

3. The method of claim 1 , wherein subsequent to the forming the slit in the softened region, a first portion of the glass sheet positioned on a first side of the slit and a second portion of the glass sheet positioned on a second side of the slit opposite the first portion are attached to one another by a membrane that is thinner than the glass sheet; and the preferentially applying heat to the slit region severs the membrane to separate the first portion and the second portion of the glass sheet from one another.

4. The method of claim 1 , wherein the forming the slit in the softened region causes at least part of the first glass cladding layer to move toward the second glass cladding layer.

5. The method of claim 4 , wherein the forming the slit in the softened region causes the first glass cladding layer and the second glass cladding layer to move into contact with each other.

6. The method of claim 1 , wherein the core layer comprises a tension of at least about 30 MPa.

7. The method of claim 1 , wherein the forming the slit in the softened region comprises shearing the softened region and moving an edge of the first glass cladding layer and an edge of the second glass cladding layer toward each other.

8. The method of claim 1 , wherein:

the forming the slit in the softened region comprises passing the softened region of the glass sheet between a first shearing member and a second shearing member in a traveling direction; and

the first shearing member and the second shearing member are misaligned with one another in the traveling direction to urge an edge of the first glass cladding layer adjacent to the slit and an edge of the second glass cladding layer adjacent to the slit toward each other.

9. The method of claim 1 , wherein:

the preferentially heating the region of the glass sheet comprises moving one of a first heating unit and the glass sheet relative to the other;

the forming the slit in the softened region comprises moving one of a shearing unit and the glass sheet relative to the other; and

the preferentially applying heat to the slit region comprises moving one of a second heating unit and the glass sheet relative to the other.

10. The method of claim 9 , wherein the first heating unit, the shearing unit, and the second heating unit are coupled to one another such that moving the glass sheet relative to the coupled first heating unit, shearing unit, and second heating unit causes the first heating unit, the shearing unit, and the second heating unit to move successively along a path on the glass sheet.

11. The method of claim 9 , wherein the first heating unit, the shearing unit, and the second heating unit are aligned with one another in a traveling direction, and the method further comprises moving the glass sheet relative to the first heating unit, the shearing unit, and the second heating unit in the traveling direction to cause the first heating unit, the shearing unit, and the second heating unit to progress successively along a path on the glass sheet.

12. The method of claim 11 , wherein the glass sheet comprises a glass ribbon moving continuously relative to the first heating unit, the shearing unit, and the second heating unit in the traveling direction, and the path extends substantially parallel to a side edge of the glass ribbon.

13. The method of claim 1 , wherein the preferentially applying heat to the slit region comprises directing a flame toward the slit region of the glass sheet.

14. The method of claim 1 , wherein the softening temperature of the glass sheet is the higher of a softening temperature of the core layer and a softening temperature of the first and second cladding layers.