Patent GB-483771-A (GB)
Title: Improvements in or relating to a process of and machine for making stem units for electrical apparatus
IPC: H01J9/32
Filed: 1937-02-27
Abstract: 483,771. Sealing wires into vitreous material. ARCTURUS RADIO TUBE CO. Feb. 27, 1937, No. 5970. Convention date, Feb. 29, 1936. [Class 36] A process for making stem units for sealed electrical apparatus such as radio tubes comprises introducing a glass exhausting-tube 115, Fig. 8, into a hollow stem-tube 110 and placing between the two tubes a series of wires 112, 113 of nickel or the like provided with a glass bead intermediate their ends, heat then being applied to cause the fusion and flowing together of the beads, stem, and exhausting-tube into a continuous closed wall which is next perforated to provide an opening through the exhausting- tube. The fused masses may be compressed in a direction along the stem axis. In the machine shown in Fig. 6 for carrying out the process a series of rotatable heads 13-19 are mounted on a turret 12 supported by a vertical axial shaft 11 on a base plate 10, the turret being rotated intermittently by a Geneva mechanism. Each head comprises a hollow tubular member 54, Fig. 7, with a gear wheel 36 on its lower end which is supported on ball-bearings 53 in a socket 50. Rods 56, 57 mounted on pivots 58 on opposite sides of the tubular member 54 are provided at their upper ends with inwardly projecting lugs 60 carrying stem-holding jaws 61, Fig. 8, of semicircular section with recessed edges 62 to engage the flared edge of a stem tube 110, the jaws being normally pulled towards one another by a spring 63 connected between the rods 56, 57, and opened by hand grips 59 at the lower ends of the rods. A template 116 secured within the upper end of the member 54 is recessed to receive the lower ends of the leading-in and supporting-wires, which are located around the circumference of an exhausting tube 115 held in manually-controlled jaws in a support 64 provided above the stem jaws 61. A plunger 85 located within the upper end of the member 54 is mounted on a rod 86 which is moved vertically upwardly in two successive movements against the action of a spring 89 by means of a vertical cam rod 91, Fig. 7, which encounters a cam surface 108, Fig. 6, during travel of the head. The various elements of the stem unit are inserted in a head at positions 13 and 14, and are subjected to heating at position 15 by two pairs of burners pointed towards the lower part of the stem tube and the glass beads about the wires. Between positions 15 and 16 the plunger 85 is moved upwardly to bring the lower end of the exhaust tube flush with the lower end of the stem. Increased heat is applied at positions 16, 17 producing fusion of the beads, stem wall, and end of the exhaust tube, this fusion being facilitated and directed by downward movement of a compressor head 107 upon the upper end of the tube 115 and a simultaneous upward movement of the. plunger 85, which produce compression of the glass mass. At position 18 less heat is applied and a pressure of air through a nozzle 19 into the exhaust tube forces a central opening through the glass at the base of the stem. The stem unit is cooled at position 19 and removed at position 13.