US 3,998,618 A · Method for making small gas-filled beads

Abstract

A method and apparatus are disclosed for making small gas-filled beads by locating a heat deformable tube on top of a heated platen in a controlled atmosphere chamber, with a multiple, spaced knife-edge structure located on top of the tube. When the temperature of a tube is raised to its softening temperature, gravity forces the knife edges through the tube, sealing the tube into separated compartments or ampuls with gas in the interior of each compartment. The articles are cooled below the softening temperature of the tube, are separated into ampuls and then the ampuls are reheated above the softening temperature to the working temperature of the tube in a sphere forming cycle under conditions of carefully maintained temperature and pressure such that the surface tension of the glass coupled with the gas within the ampul causes the ampul to take on the shape of a sphere with uniformly thick walls and size, dependent on the temperature and pressure conditions during the reheating cycle.

Claims11

Dependent claims

A method of forming gas-filled enclosures comprising the steps of

providing a sealed hollow structure containing a gas and having heat deformable walls which are deformable above a predetermined softening temperature, said structure being maintained at a temperature below the softening temperature of said walls, whereby said structure is substantially rigid;
heating the hollow structure provided in a sealed furnace in an unrestrained substantially free condition above the softening temperature of said walls to a range at which said walls become stretchable while still maintaining the original integrity of the hollow structure;
initially controlling the pressure of the gas within said sealed furnace such that said hollow structure is permitted to expand;
increasing the pressure of the gas surrounding said hollow structure when a desired size is obtained to a pressure which balances the forces of expansion;
and
cooling the hollow structure in the sealed pressurized furnace below said softening temperature to form a substantially rigid hollow structure of a predetermined size.

3 more elements

A method for making small spheres filled with ionizable gas having uniform ionization characteristics comprising the steps of

providing a heat deformable tube of predetermined dielectric constant,
cleaning said tube to remove gaseous and particulate contaminants,
sealing one end of said tube,
evacuating said sealed tube,
filling said evacuated tube with ionizable gas by introducing said ionizable gas into the evacuated portion of said tube,
sealing the other end of said tube,
placing said tube on a heatable platen in a controlled atmosphere furnace,
sealing and severing said tube by placing a multiple-blade knife-blade unit having a number of spaced vertically oriented blades on said tube with the knife blades running across said tube, introducing an inert gas into said furnace, and, raising the temperature of said tube to its softening temperature thereby to form closed hollow gas-filled structures,
lowering the temperature below said softening temperature,
cleaning said hollow gas-filled structures to remove exterior contaminants,
providing an inert atmosphere around said hollow gas-filled structures,
heating said hollow gas-filled structures above said softening temperature while maintaining a predetermined pressure profile of said inert atmosphere with respect to that of the gas within said hollow gas-filled structures during the time the temperature of said structures is above said softening temperature to allow formation of spheres of a predetermined size, and
lowering the temperature of said spheres below said softening temperature.

10 more elements

Dependencies are inferred from the claim text.

Method for making small gas-filled beads

Life of this patent

Method for making small gas-filled beads

Life of this patent

Abstract

Claims11