Method and apparatus for continuously cutting glass

Patent metadata

Field	Value
Publication number	US-10407336-B2
Application number	US-201715686514-A
Country	US
Kind code	B2
Filing date	Aug 25, 2017
Priority date	Mar 27, 2015
Publication date	Sep 10, 2019
Grant date	Sep 10, 2019

Abstract

A method for cutting a thin glass including the steps of guiding, by a transport device, the thin glass ribbon over a levitation support, and directing, within a range of the levitation support, a laser beam onto the thin glass ribbon, which heats up the thin glass ribbon at an impingement point of the laser beam. The method also includes the step of blowing, by a cooling jet generator, a cooling fluid onto the track heated by the laser beam so that a region heated by the laser beam is cooled down and a mechanical stress is created. The cooling fluid contains vapor of a liquid at a saturation ratio of at least 0.5 or a plurality of liquid droplets. The liquid droplets form a contact angle on a surface of the thin glass ribbon which is smaller than that of water on the same surface.

First claim

What is claimed is:

1. A method for cutting a thin glass ribbon having a thickness of at most 400 μm along a longitudinal extension direction of the thin glass ribbon, for severing beads on edge portions of the thin glass ribbon, the method comprising the steps of:
guiding, by a transport device, the thin glass ribbon along the longitudinal extension direction thereof over a levitation support;
directing, within a range of the levitation support, a laser beam onto the thin glass ribbon, which heats up the thin glass ribbon at an impingement point of the laser beam, and moving the thin glass ribbon in the longitudinal extension direction below the laser beam so that the laser beam draws a track running in the longitudinal extension direction of the thin glass ribbon; and
spraying, by a cooling jet generator configured as an ink-jet printing head, a cooling fluid in the form of sequentially deposited, separated, and isolated liquid droplets onto the track heated by the laser beam so that a region heated by the laser beam is cooled down and a mechanical stress is created which causes propagation of a stress crack separating the glass ribbon in the longitudinal direction along the track of the laser beam, wherein each said liquid droplet forms a contact angle on a surface of the thin glass ribbon, which is smaller than that of water on the same surface, such that said beads are separated from the thin glass ribbon to improve a quality and a strength of the edge portions of the thin glass ribbon, and wherein the thin glass ribbon is guided so that a difference between mechanical stresses that are effective on an upper surface of said thin glass ribbon and on a lower surface of the thin glass ribbon in the longitudinal extension direction of the thin glass ribbon is less than 0.25 MPa.

2. The method according to claim 1 , wherein, by way of a scoring device, an initial defect is introduced at a leading end of the thin glass ribbon prior to an impingement of the laser beam, which defect intersects said point of impingement of the laser beam so as to initiate the stress crack.

3. The method according to claim 2 , wherein once the stress crack has been initiated, the scoring device is removed from the surface of the thin glass ribbon during a crack propagation, thereby terminating a scoring of the scoring device.

4. The method according to claim 3 , wherein the scoring device comprises a scoring wheel, wherein a contact pressure of the scoring wheel when introducing the initial defect is less than 4 N.

5. The method according to claim 1 , wherein said thin glass ribbon has a length of at least 10 meters in the longitudinal extension direction of the thin glass ribbon.

6. The method according to claim 1 , wherein a fluid is supplied to the levitation support, which fluid is at a pressure in a range from 0.1 to 4 bar.

7. The method according to claim 1 , wherein the transport device exerts a tensile stress on the thin glass ribbon, at least within the range of the levitation support, which tensile stress is effective in the longitudinal extension direction.

8. The method according to claim 1 , wherein within the range of the levitation support, a tensile stress in a range from 0.5 MPa to 10 MPa is applied to the thin glass ribbon in the longitudinal extension direction.

9. The method according to claim 1 , wherein the thin glass ribbon is advanced along its longitudinal extension direction passing between a roller arrangement.

10. The method according to claim 1 , wherein the thin glass ribbon is advanced along the longitudinal extension direction thereof between a pair of roller arrangements on either side of the levitation support, in a manner so that a tensile stress effective within the range of the levitation support is exerted on the thin glass ribbon in the longitudinal extension direction thereof.

11. The method according to claim 1 , wherein a gas flow is blown onto an upper surface of the thin glass ribbon within the range of the levitation support, so as to attenuate at least one transversal wave propagating across the thin glass ribbon.

12. The method according to claim 1 , wherein said cooling fluid which is sprayed comprises liquid droplets containing at least one of:
water including surfactants, and
at least one of a monohydric alcohol, a polyhydric alcohol, and an ethylene glycol.

13. The method according to claim 1 , wherein said cooling fluid is sprayed onto the surface of said thin glass ribbon, said cooling fluid comprises liquid droplets that form a contact angle of less than 40° on the surface of the thin glass ribbon.

14. The method according to claim 1 , wherein a tensile force is exerted on the thin glass ribbon in the longitudinal direction, wherein within the range of the levitation support a ratio Δσ/σ is less than 0.5, wherein Δσ is a difference of the tensile stresses acting in the longitudinal extension direction on an upper surface and on a lower surface of said thin glass ribbon, and σ is the tensile stress created by the tensile force applied in the longitudinal extension direction.

15. The method according to claim 1 , wherein by virtue of a bulging of the thin glass ribbon at the point of impingement of the laser beam, a tensile stress is exerted perpendicularly to the longitudinal extension direction of the thin glass ribbon so that a ratio σ/α of tensile stress σto a coefficient of linear thermal expansion α is at least 0.07*10 −6 MPa*K −1 .

16. The method according to claim 1 , wherein a temperature difference ΔT which is achieved by the heating by way of the laser beam and the cooling by way of the cooling fluid assumes at least a value of ΔT=(7·K Ic )/(5·α 1/2 ·CTE·E), wherein a parameter K Ic designates a fracture toughness, a parameter designates a critical crack length, a factor CTE designates a coefficient of linear thermal expansion, and E represents a Young's modulus of the glass.

17. The method according to claim 1 , wherein the laser beam is shaped so that a footprint of the laser beam has an elongated shape, and wherein the laser beam is directed onto the surface of the thin glass so that a longitudinal extension direction of said footprint of the laser beam is aligned in an advancement direction, and wherein the elongated shape of the beam footprint is asymmetric so as to exhibit different intensity profiles at the ends of the beam footprint in a manner so that an increase in intensity at a leading end that is first sweeping over the thin glass ribbon is steeper than a decrease in intensity at the opposite, trailing end.

18. An apparatus for cutting a thin glass ribbon having a thickness of at most 400 μm along a longitudinal extension direction of the thin glass ribbon, for severing beads on edge portions of the thin glass ribbon, said apparatus comprising:
a levitation support;
a transport device for guiding the thin glass ribbon along the longitudinal extension direction thereof over the levitation support;
a laser for directing a laser beam onto the thin glass ribbon within a range of a levitation support and for heating up the thin glass ribbon at an impingement point of the laser beam so that the laser beam draws a track running in the longitudinal extension direction of the thin glass ribbon when the thin glass ribbon is moved by the transport device below the laser beam in the longitudinal direction;
a cooling jet generator configured as an ink-jet printing head for spraying a cooling fluid in the form of sequentially deposited, separated, and isolated liquid droplets onto the track that is heated by the laser beam so

Assignees

• Schott Ag

Inventors

• Rossmeier Thomas
• Ortner Andreas
• VOGT Jürgen
• Habeck Andreas
• Ottermann Clemens
• Förtsch Dirk
• Breitbach Christian
• Behle Stephan

Classifications

• B65G49/065

  supported partially or completely on fluid cushions, e.g. a gas cushion (in general B65G51/00) · CPC title

• C03B33/091 Primary

  using at least one focussed radiation beam, e.g. laser beam (C03B33/0955 takes precedence) · CPC title

• C03B33/03

  Glass cutting tables; Apparatus for transporting or handling sheet glass during the cutting or breaking operations · CPC title

• C03B33/0235

  Ribbons · CPC title