Methods of and apparatus for heating a glass tube

A method of heating successive portions of a glass tube while controlling the temperature profile along said tube, said method comprising the steps of:

• rotatably supporting a glass tube;
• confining a portion of the length of the tube at least partially with an arcuate surface of a housing which is spaced from the tube;
• mounting said housing so that said surface may be moved toward or away from said tube;
• directing a plurality of combustible gas flows through a plurality of passageways which extend through said housing and open to said arcuate surface;
• cooling at least those portions of the housing and walls which define the passageways adjacent to said arcuate surface to prevent oxidation thereof without cooling said tube;
• and
• moving the housing reciprocally along the length of the tube to cause a heating of successive portions of the length of the tube while rotating the tube about its longitudinal axis;
• and
• spacing said surface a predetermined distance from the tube to control the temperature profile along each successive portion of the length of the tube.

A method of heating successive portions of a length of glass tube, said method comprising the steps of:

• rotatably supporting a glass tube along an axis which extends along the length of the tube;
• enclosing at least partially a portion of the length of the tube with an arcuate surface of a housing, said surface being spaced from the tube a predetermined distance;
• mounting said surface so that the distance between it and the tube is capable of being varied;
• directing a flow of a first combustible gas through each of a plurality of nozzles which are mounted in said housing and which open to said surface;
• directing a flow of a second combustible gas between said plurality of nozzles to mix with said first combustible gas along said arcuate surface to produce a flame which heats said tube;
• cooling the housing and walls of the nozzles at least adjacent the arcuate surface to prevent oxidation of the material forming the housing and the nozzles without cooling said tube;
• moving the arcuate surface reciprocally along the rod to cause a heating of successive portions of the length of the tube while rotating the glass tube;
• and
• spacing the surface a predetermined distance from the tube to control the temperature profile along each successive portion of the length of the tube.

An apparatus for heating a glass tube, which includes:

• means for supporting a tube for rotation about its longitudinal axis;
• means for including a plurality of passageways for directing a flow of combustible gases toward said tube;
• means for cooling at least those portions of the passageways which are adjacent the tube to inhibit contamination of the passageways and thereby prevent contamination of the tube;
• means for providing a variable confinement of the heat to said portion of the length of the tube to control the temperature profile along said portion of the length of said tube, said means for providing a variable confinement including an arcuate surface spaced equidistantly from the tube for confining at least partially the tube, said means for controlling the temperature profile including means for mounting the arcuate surface for movement toward or away from the tube;
• means for causing relative motion between the tube and the confining means along the tube to cause successive portions of the length of the tube to be heated;
• and
• means for rotating the tube about an axis which extends along the length of the tube.