Abstract This application discloses the severing of rod-like and relatively thick walled hollow glass articles formed from relatively high expansion coefficient glasses, e.g., rod, tumblers, tubing, cathode ray bulbs and the like. Severing is accomplished by repeatedly rotating the article to be severed while directing, against the surface of the article, a relatively sharply focused intense beam of coherent radiant energy of a wavelength such that the article will absorb a substantial amount of the radiant energy. It has been found that glass is highly opaque to, or highly absorptive of, radiant energy of a wavelength of 10.6 microns, and coherent radiant energy of this type may be conveniently provided by a laser of the CO2 type, which equipment is available from commercial sources. The article being severed must be rotated sufficiently rapidly to prevent the laser from damaging or burning the surface thereof by localized overheating. Severing of the article is effected by cracking along the line repeatedly traced by the laser beam, the cracking being caused by the temperature differential between the glass along this line and glass in regions closely proximate thereto. The development of temperature differentials in glass articles satisfactory for cracking is relatively easy to accomplish due to the relatively poor thermal conductivity of glass and the relatively poor strength of glass in tension.
THE METHOD OF SEVERING A PORTION OF A ROD-LIKE OR RELATIVELY THICK-WALLED HOLLOW GLASS ARTICLES FROM THE REMAINDER OF THE ORGINAL PORTION WITHOUT VISIBLE DAMGE TO THE EDGE OR ADJACENT SURFACE PORTIONS THEREOF, SAID GLASS ARTICLE BEING FORMED FROM A GLASS COMPOSITION WHOSE COEFFICIENT OF EXPANSION IS NOT SUBSTANTIALLY LOWER THAN THAT OF SODA-LIME GLASS, SAID METHOD COMPRISING THE STEPS OF: EMITTING A LASER BEAM AT A WAVELENGHT OF 10.6 MICRONS BY AN ALTERNATING CURRENT CO2 TYPE LASER UNIT AT A POWDER NOT SUBSTANTIALLY LESS THAN 20 WATTS NOR SUBSTANTIALLY HIGHER THAN 500 WATTS, SAID LASER BEAM, AT SUCH WAVELENGHT BEING ABSORBDED TO A SUBSTANTIAL DEGREE BY GLASS; INTERPOSING THE GLASS ARTICLE IN THE PATH OF THE LASER BEAM; FOCUSING THE LASER BEAM TO A VERY SMALL SPOT ON THE DESIRED LINE OF SEVERNCE OF THE GLASS ARTICLE; AND ROTATING THE ARTICLE ABOUT ITS LONGITUDINAL CENTER AXIS AT A SPEED NOT SUBSTANTIALLY LOWER THAN 200 REVOLUTIONS PER MINUTE AT ALL TIMES WHILE THE LASER BEAM IS IMPINGING THEREAGAINST TO CAUSE THE LASER BEAM IS IMPINGING A CIRCUMFERENTIAL PATTERN ABOUT THE GLASS ARTICLE, SAID PATTERN BEING COINCIDENT WITH THE DESIRE LINE OF SEPARATION OF SAID PORTION FROM SAID REMAINDER, SAID ROTATION BEING CONTINUED UNTIL THE HEATING EFFECT OF SAID LASER BEAM ALONG SAID DESIRED LINE OF SEPARATION IS SUFFICIENT TO ESTABLISH THERMAL STRESSES IN SAID ARTICLE WHICH ARE SUFFICIENT TO CAUSE SAID ARTICLE TO CRACK CLEANLY ALONG SAID LINE, SAID SEVERING BEING EFFECTED ENTIRELY BY THERMAL STRESSES IN THE GLASS ARTICLE ESTABLISHED BY THE IMPINGEMENT OF THE LASER BEAM AGAINST THE ROTATING ARTICLE, THE TEMPERATURE OF THE ARTICLE ALONG THE LINE OF SEPARATION REMAINING BELOW THE TEMPERATURE WHERE THE ARTICLE WILL SHOW COLOR AT ALL TIMES DURING THE IMPINGEMENT OF THE LASER THEREAGAINST, THE SEPARATED PORTION OF THE ARTICLE BEING CHARACTERIZED BY A RIM IMMEDIATELY ADJACENT THE LINE OF SEPARATION WHICH A SUBSTANTIALLY FREE OF THE VISIBLE EFFECTS OF OVERHEATING .
Claim 2
Independent Claim
320 words
THE METHOD OF SEVERING A PORTION OF A ROD-LIKE OR RELATIVELY THICK-WALLED HOLLOW GLASS ARTICLES FROM THE REMAINDER OF THE ORGINAL PORTION WITHOUT VISIBLE DAMGE TO THE EDGE OR ADJACENT SURFACE PORTIONS THEREOF, SAID GLASS ARTICLE BEING FORMED FROM A GLASS COMPOSITION WHOSE COEFFICIENT OF EXPANSION IS NOT SUBSTANTIALLY LOWER THAN THAT OF SODA-LIME GLASS, SAID METHOD COMPRISING THE STEPS OF: EMITTING A LASER BEAM AT A WAVELENGHT OF 10.6 MICRONS BY AN ALTERNATING CURRENT CO2 TYPE LASER UNIT AT A POWDER NOT SUBSTANTIALLY LESS THAN 20 WATTS NOR SUBSTANTIALLY HIGHER THAN 500 WATTS, SAID LASER BEAM, AT SUCH WAVELENGHT BEING ABSORBDED TO A SUBSTANTIAL DEGREE BY GLASS; INTERPOSING THE GLASS ARTICLE IN THE PATH OF THE LASER BEAM; FOCUSING THE LASER BEAM TO A VERY SMALL SPOT ON THE DESIRED LINE OF SEVERNCE OF THE GLASS ARTICLE; AND ROTATING THE ARTICLE ABOUT ITS LONGITUDINAL CENTER AXIS AT A SPEED NOT SUBSTANTIALLY LOWER THAN 200 REVOLUTIONS PER MINUTE AT ALL TIMES WHILE THE LASER BEAM IS IMPINGING THEREAGAINST TO CAUSE THE LASER BEAM IS IMPINGING A CIRCUMFERENTIAL PATTERN ABOUT THE GLASS ARTICLE, SAID PATTERN BEING COINCIDENT WITH THE DESIRE LINE OF SEPARATION OF SAID PORTION FROM SAID REMAINDER, SAID ROTATION BEING CONTINUED UNTIL THE HEATING EFFECT OF SAID LASER BEAM ALONG SAID DESIRED LINE OF SEPARATION IS SUFFICIENT TO ESTABLISH THERMAL STRESSES IN SAID ARTICLE WHICH ARE SUFFICIENT TO CAUSE SAID ARTICLE TO CRACK CLEANLY ALONG SAID LINE, SAID SEVERING BEING EFFECTED ENTIRELY BY THERMAL STRESSES IN THE GLASS ARTICLE ESTABLISHED BY THE IMPINGEMENT OF THE LASER BEAM AGAINST THE ROTATING ARTICLE, THE TEMPERATURE OF THE ARTICLE ALONG THE LINE OF SEPARATION REMAINING BELOW THE TEMPERATURE WHERE THE ARTICLE WILL SHOW COLOR AT ALL TIMES DURING THE IMPINGEMENT OF THE LASER THEREAGAINST, THE SEPARATED PORTION OF THE ARTICLE BEING CHARACTERIZED BY A RIM IMMEDIATELY ADJACENT THE LINE OF SEPARATION WHICH A SUBSTANTIALLY FREE OF THE VISIBLE EFFECTS OF OVERHEATING .
Claim 3
Dependent Claim
31 words
The method according to claim 1 and further comprising directing a flame from a small gas burner adjacent the rotating glass article at a point on said desired line of separation.
Claim 4
Dependent Claim
22 words
The method of claim 1 wherein said article is rotated at a rotational speed not substantially higher than 900 revolutions per minute.
Claim 5
Dependent Claim
36 words
The method according to claim 1 wherein the article is rotated at a speed of rotation which is asynchronously related to the a.c. excitation frequency of the laser beam emitted by the alternating current laser unit.