Patent GB-951683-A (GB)
Title: Improvements in or relating to the manufacture of low pressure mercury vapour fluorescent electric discharge lamps
Inventor: ACKROYD ERNEST WALTER
IPC: H01J9/20
Filed: 1961-09-07
Abstract: 951,683. Apparatus for applying starting stripes to discharge lamps. GENERAL ELECTRIC CO. Ltd. Aug. 27, 1962 [Sept. 7, 1961], No. 32162/61. Headings H1D and H1J. [Also in Division B2] Starting stripes are coated on the exterior surface of the envelopes of discharge lamps in apparatus comprising an indexing conveyer moving in a closed path and having holders for supporting the envelopes with their axes vertical, a striping head having at least one roller on a horizontal axis, means for producing working strokes of the roller on a vertical path extending beyond the top and bottom of the envelope synchronized with the movement of the conveyer so that a different holder is brought into coating position between successive working strokes of the roller, spring biasing means for holding the edge of the roller in contact with an envelope during the working-stroke and a reservoir containing a supply of stripe forming paint from which the paint can be fed to the edge of the roller. The roller may be held in contact with the envelope during the upward stroke and moved into non-operative position during the down stroke. The paint may consist of silver oxide and lead borate in powdered form in a suspension in methyl alcohol and glycerine, the envelopes being subsequently baked to reduce the silver oxide to silver and fuse the lead borate. The invention is applied to discharge tubes coated internally with fluorescent material and containing mercury and a filling of rare gas at a pressure of a few millimetres of mercury. The conveyer 1, Fig. 1, consists of two endless chains 4 passing round two pairs of sprocket-wheels 2, each pair being on a common shaft 3, and vertical battens 6 uniformly spaced around the chains and carrying spring clips 7 to support the envelopes 8. One of the shafts 3 is driven by a motor M through an indexing mechanism 9. The striping head 10 comprises a carriage 11 slidably mounted on vertical guide rails 12, a horizontal groove 17 on the carriage engaging a bar 16 carried by an endless chain 15 extending between sprocket wheels 13, the lower of which is driven from the motor M through a reduction gear 18. The carriage 11 carries two striping rollers 19, each rotatable on a horizontal spindle 22, Fig. 2, carried by rods 26 on a bar 25. Paint is fed to the rollers 19 from reservoirs 29 by feed pipes 30, 31. The rollers are biased towards envelopes in coating position by springs 34 during the upward movement, a cam 38 near the top of the guide rails engaging a lever 27 on the bar 25 at the end of the upstroke to pivot the rollers away from the envelopes, the lever being held in the position in which the rollers are retracted by a spring catch 39 during the downstroke and being then released from the catches by a second cam 41. The indexing movement is such that each roller effects striping of alternate envelopes. Each of the fed pipes 31 contains a needle valve 33 for controlling the rate of feeding of the paint. The top of each reservoir is connected to a compressor (not shown) through an electrically operated on-off valve 43, microswitches 44, 45 at the top and bottom of the guide rails effecting the closing of the valve 43 at the end of the upstroke and the re-opening at the end of the downstroke. A microswitch (not shown) may also be provided opposite each roller so as to engage the envelope, the switch preventing the opening of the valve 43 unless an envelope is in coating position. Each reservoir may contain an agitator for preventing gelling of the paint and the settling of the silver oxide and lead borate particles.