Method and apparatus for subdividing a gas filled glass tube with a laser

A method of producing miniature tubular radioactive light sources by subdividing into individual sealed segments a long, sealed glass tube filled with a radioactive gas, the tube having a longitudinal axis, the method comprising the steps of simultaneously:

• holding a long glass tube in a stationary position in an ambient atmosphere having a higher pressure than the gas in the tube;
• moving a laser beam across the surface of the long glass tube along a cut line transverse to the longitudinal axis of the tube to heat and soften the tube until the tube divides to form ends and collapses to seal the divided ends;
• and
• decreasing the intensity of the laser beam to anneal the divided ends.

A method of subdividing into individual sealed segments a long, sealed glass tube coated on the inside with a luminophor and filled with a radioactive gas, the tube having a longitudinal axis, the method comprising the steps of:

• directing a focused laser beam at the tube in an ambient atmosphere having a higher pressure than the gas in the tube;
• introducing relative movement between the laser beam and the tube transverse to the longitudinal axis of the tube to heat and soften the tube along a cut line until the tube divides to form ends and collapses to seal the divided ends;
• and
• increasing the intensity of the laser beam during the relative movement to preheat the cut line uniformly to a temperature below the fusion temperature of the tube before division of the tube begins.

A method of subdividing into individual sealed segments a long, sealed glass tube coated on the inside with a luminophor and filled with a radioactive gas, the tube having a longitudinal axis, the method comprising the steps of:

• directing a laser beam at the tube in an ambient atmosphere having a higher pressure than the gas in the tube;
• introducing relative movement between the laser beam and the tube transverse to the longitudinal axis of the tube to heat and soften the tube along a cut line until the tube divides to form ends and collapses to seal the divided ends;
• and
• changing the velocity of the relative movement between the laser beam and the tube to uniformly heat the glass along the cut line.

A method of subdividing into individual sealed segments a long, sealed glass tube coated on the inside with a luminophor and filled with a radioactive gas, the tube having a longitudinal axis, the method comprising the steps of:

• holding the tube at two spaced apart positions along the longitudinal axis;
• directing a laser beam at the tube between the holding positions in an ambient atmosphere having a higher pressure than the gas in the tube;
• introducing relative movement between the laser beam and the tube transverse to the longitudinal axis of the tube;
• focusing the laser beam during an initial portion of the moving step to heat and soften the tube along a cut line until the tube divides to form ends and collapses to seal the divided ends;
• and
• defocusing the laser beam during a final portion of the moving step of anneal the divided ends of the tube.

In combination with apparatus for subdividing a long radioactive gas-filled sealed glass tube into individual sealed tube segments by means of a laser beam, a holder for the long tube comprising:

• a body having an elongated slot in which the tube slidably fits;
• means for permitting the laser beam to pass through the body to the slot in the region where the long tube is to be subdivided;
• means for holding the long tube on both sides of the region where it is to be subdivided;
• and
• means for pushing the long tube through the slot.

A laser glass working system comprising:

• a laser source that emits a laser beam;
• a work station remote from the laser source, the work station including a tube holder for holding an elongated glass tube having two flat oppositely disposed side surfaces, the holder having laser access opening means exposing the flat side surfaces of the tube along a region of its length;
• means for splitting the beam emitted by the laser source into two parts;
• means for directing the two parts of the beam at the work station from opposite directions so the two parts of the beam directed at the work station from opposite directions pass through the laser access opening means;
• and
• means for scanning the two parts of the beam directed at the work station back and forth in the same plane.

A laser working system for cutting along glass tubes at a work station, the system comprising:

• a laser source that emits a laser beam of variable intensity, remote from the work station;
• a glass tube holder at the work station;
• means for directing the laser beam at the tube holder;
• a source of a periodic signal;
• means responsive to the periodic signal for producing a corresponding periodic relative movement between the tube holder and the laser beam directed at the tube holder;
• and
• means responsive to the periodic signal for varying the intensity of the laser beam to synchronize the laser beam intensity variations to the relative movement between the laser beam and the tube holder.

A laser glass working system comprising:

• a laser source that emits a laser beam;
• a work station remote from the laser source adapted to hold a glass tube;
• means for splitting the beam emitted by the laser source into two parts;
• means for directing the two parts of the beam at the work station from opposite directions;
• means for scanning the two parts of the beam directed at the work station back and forth in the same plane;
• and
• means for modulating the intensity of the laser beam emitted by the laser source in increasing fashion while scanning the two parts of the beam back and forth to first heat slowly and then cut rapidly the tube at the work station.

A laser working system comprising:

• a laser source that emits a lase beam;
• a work station remote from the laser source;
• means for splitting the beam emitted by the laser source into two parts;
• means including deflector means for directing the two parts of the beam at the work station from opposite directions for movement in the same plane;
• a source of an electrical sine wave signal;
• and
• means responsive to the source of the electrical signal for controlling the deflector means to deflect the two parts of the beam directed at the work station back and forth in the same plane sinusoidally.