Patent GB-499413-A (GB)
Title: Improvements in or relating to machines for making electric incandescent lamps or the like
IPC: H01J9/38
Filed: 1937-07-30
Abstract: 499,413. Making electric incandescent lamps. HOFMANN & CO., A. July 30, 1937, No. 21195. Convention date, May 17. [Class 39 (ii)] General arrangement.-In a lamp-making machine for sealing the bulb to the stem of a lamp and exhausting and tipping-off the lamp in automatic succession in a travelling series of heads, each head is provided with a support for the upright stem, and above that a holder for positioning the bulb with its neck surrounding the stem flange, burners being also provided for heating and fusing together the bulb neck and stem flange before exhausting, and other burners for heating the exhaust tube to tip-off the exhausted lamp, means being provided for raising the bulb holder of each head after sealing-in in order to stretch the hot seal. and further means at a subsequent point of travel again raising the holder to lift the exhausted lamp and thereby stretch the heated exhaust tube during tipping-off. The machine is in the form of a rotary turret provided around its periphery with a series of thirty-heads which are advanced intermittently through thirty stations at various ones of which the operations are performed. Between stations 1 and 3 each head is supplied with a stem, for example by hand, the flare of the stem being placed upon a support 86, Fig. 7. At station 4 the bulb is placed in position on a holder 78, either by hand or by feeding-mechanism of known type. Between stations 5 and 13 each head, with bulb and stem, is rotated continuously by means of a driving-belt engaging a pulley thereon, whilst flames are applied to the bulb neck to fuse it to the stem flare before they reach station 11.. Between stations 8 and 11 an air stream is flowed through each head to prevent overheating and damage to the coupling-plug carrying the stem. At station 12 the glass skirt below the bulb and stem seal is blown off by air pressure accompanied by an intense flame. At station 13 rotation of the head ceases, the exhaust tube e is gripped by its surrounding plug and coupled for exhausting and, at or approaching station 15, the bulb holder 77 is lifted slightly to stretch the fused seal between bulb and flare. The bulb holder may next be lowered, leaving the sealed-in lamp supported only by its exhaust tube, or the holder may remain in position to steady the lamp. At station 15 the lamp is exhausted by a preliminary or testing vacuum, and at station 16 it is tested by detecting means, and isolated and marked or ejected if leaky. The final or full vacuum is applied from stations 18-20. Therebeyond, exhaustion ateach station may be alternated with flushing or partial filling by an inert gas during travel between stations. For gas-filled lamps the final gas filling may be admitted between stations 28 and 29. If a vacuum lamp is to be manufactured the final evacuation may be at station 29. Between stations 25 and 27 the loosely extending leading-in wires are pulled laterally frontward from the tube e, preparatory to tipping-off, and at station 28 preheating of the exhaust tube is commenced in readiness for tipping-off by a device at station 29. During tipping-off the lamp is lifted to stretch the exhaust tube, this also being part of the outfeeding operation. At station 30 the discarded pieces of skirt and exhaust tube are removed, either automatically or manually. Turret and work-receiving heads.-Fig. 7 shows a portion of the turret 31 and one of the work-receiving heads, supported by a cylindrical bearing 64 on the outer flange 63 of the turret. The underside of the turret is provided with thirty downwardly projecting studs 53, Figs. 3 and 5 (not shown), which are engaged by a driving-cam on the periphery of a wheel and arranged so that each rotation of the wheel advances the turret to the extent of one station. Each head comprises a sleeve 69 with a driving-pulley 71 at its lower end to engage a belt 37 whereby the sleeve is rotated between stations 5 and 13. A notch 72 is provided in the pulley to co-operate with a dog 150 which is actuated at station 13 to arrest rotation and lock the parts in a definite angular position. Sleeve 69 has no vertical movement. A sleeve 73 located within sleeve 69 is, however, arranged for vertical movement and is rotated by coupling its upper flange 75 to the flange 70 of sleeve 69 by means of a vertical stud projecting from the latter flange into an aperture in the flange 75. Flange 75 supports rods 76 with a top piece 77 provided with three interior lugs which constitute the bulb support. A third or stem-supporting sleeve 85 slides vertically within the sleeve 73 and is rotated with it by a friction coupling comprising a series of radial pins 82 which are disposed in apertures below flange 75 of sleeve 73 and are pressed inwardly upon sleeve 85 by a surrounding coil-spring. The upper end of sleeve 85 has a perforated top 87 on which the stem flare rests initially, and the lower end of the sleeve carries or rests on a flanged member 89 co-operating with a track or cam 90 which extends around the orbit of travel and has portions at different levels whereby the sleeve 85 may be lowered and lifted at intervals. Within sleeve 85 is a fourth or fixed sleeve 95, the the two being spaced apart and providing an annular channel 94 by which air is supplied up through members 86 and 87 for delivery near the fusing or sealing-in point. The upper end of the sleeve 95 carries a hollow top piece tu receive the stem tube e and encloses a soft rubber plug 99 with a bore such that normally the stem tube can be easily inserted therein until the plug has been compressed to grip the pipe. This compression is effected by an exhaust sleeve 100 located within sleeve 95 with its upper end in contact with the rubber plug, and adapted to be raised by a rotary cam disc 104 at its lower end engaging a fixed cam disc 105. To effect rotation, the upper cam disc is provided with a radially projecting arm 106 which is swung to couple at station 13 and uncouple at station 30 by means of a vertical pill 107 on a rocking-arm 108. At certain stations a current of air may be caused to rise in the annular space between sleeves 85 and 95, this air being admitted from a fixed conduit 110 through ports 111 controlled by valves 115. Bulb-lifting.-The lifting of the bulb holder 77 to stretch the warm seal between bulb neck and stem flare is effected near station 14 by means of a fixed cam acting on the underside of the flange 75 of the holder. The flange rides up the cam incline, and the head pauses at station 14 with the disc at the cam apex while the glass hardens. The means for lifting the bulb to stretch the exhausting- tube at station 29 comprises a horizontal finger or bar which is forked to embrace the edge of the flange 75 of each work head and is lifted by the vertical movement .of a rod on which it is mounted, this rod being lifted by a cam at its bottom end. Exhausting and filling.-The lower end of the permanent exhaust passage 101, Fig. 7, of the head is coupled by a rubber coupling 118 to a pipe 117 from which tubes 120, 429 extend radially inward to the rotatable upper disc 426, Fig. 22, of the central control valve, where it connects to a short vertical passage 430 adapted to co-operate in turn with vertical ports in the stationary lower valve disc 427. The rotary valve disc is linked to the turret and rotates therewith. The lower valve disc 427 is connected to a central vacuum duct 443 by which the chamber 438 is connected to a final or high vacuum pump, the vacuum being connected to the heads pausing at each of stations 18 to 28 by a series of passages 445. Each disc port registers with each vacuum port, but the ports are so spaced that communication is cut off during travel between stations. Auxiliary ports 448 disposed outside the central chamber and connected to an auxiliary pump apply a preliminary vacuum to each head as it comes to stations 15 and 17. Partial flushing is. performed between stations in alternation with the exhausting, during travel of the heads from station 20 to station 28, this being effected through eight ports leading from an annular chamber 453 which is connected by a pipe 455 to a tank containing nitrogen. Tipping-off.-The tipping off mechanism comprises a pair of burners 137, Fig. 16, for concentrating flames on the glass exhaust tube. A shield in the form of a pair of cooperating plates 275 mounted on a pivot 274 on an arm 273 is provided to prevent the heat from reaching the bulb and leading-in wires. The plates 275 are normally held closed by a spring 277 and are provided with nicks 278 which form an aperture for the exhausting- tube. The arm 273 is lifted at timed intervals and then swung inwardly by the disc on the work-head operating a cam plate, so that the jaws snap around the exhausting-tube. A further movement of the head swings the shield to retracted position. Detecting leaky bulbs.-The device for detecting leaky bulbs operates at station 16 and may control means either to mark a defective lamp or actually isolate it, the lamp bulb being connected through ports in the valve discs to the open limb of a U-shaped manometer-tube containing mercury. A leaky bulb results in an inflow of air in the open limb, causing the mercury in the closed limb to rise and complete the electric circuit between two wires extending therein. This completes a relay circuit which energizes a solenoid controlling a link which produces the desired mechanical action.