Patent GB-695101-A (GB)
Title: Improvements in and relating to apparatus for manufacturing electric fluorescent discharge lamps
IPC: H01J9/46
Filed: 1947-09-05
Abstract: 695,101. Electric discharge lamps. BRITISH THOMSON-HOUSTON CO., Ltd. Sept. 5, 1947 (Sept. 6, 1946], No. 24494/47. Class 39(i) [Also in Group XI] Apparatus for making fluorescent discharge lamps is of the kind described in Specification 365,435 including two rotatable turrets each having a plurality of work stations, wherein sealing-in of electrode mounts is performed at a set of stations associated with the first turret and means are provided at a second set of stations associated with the second turret for heating the bulb to burn off a binder used for the application of a fluorescent coating to the inner surface of the bulb before the sealing-in of the electrode mounts, and for removing from the bulb combustion products evolved from the binder, the apparatus also including means for evacuating each bulb before the latter cools appreciably after removal of the combustion products therefrom and for subsequently tipping-off the bulb. Means are also provided for flushing a bulb while it is heated, e.g. in an oven, at a work station of the second set. The apparatus may also include a third turret arranged next to the second turret and having heads for holding the partly manufactured lamps, a third set of work stations associated with the third turret and mechanism for automatically transferring partly manufactured lamps from the second turret to the third turret at predetermined work stations of the second and third sets. The final exhaustion of the bulb and subsequent operations, e.g. activation of the barium carbonate coated cathodes mounted in the bulbs, are carried out at work stations of the third set. The interior of the bulb 1, Fig. 1, is coated by flushing a fluid comprising a cellulose binder having a fluorescent powder in suspension over the entire interior surface of the bulb by means of a nozzle 2 and a valve pin having an enlarged end 3, excess fluid draining into the trough 4. The coating and .drying operations are preferably performed in automatic high speed apparatus of the type described in Specification 583,679, [Group III]. The electrodecarrying stem tubes 6, Fig. 3, may be sealed into the bulb 1 by means as described in Specification 607,766 and which preferably include provision of means to produce air pressure in the bulb 1 during the sealing operation. The subsequent steps in the manufacture of the lamp are performed in a separate portion of the apparatus in which the assembled lamp 14, Fig. 4, is held in a head 15 by which the lamp is advanced by regular indexing movements thereof. The head 15 provides a port for holding and making a gas-tight connection to the exhaust tube 9 which is, upon insertion of lamp 14 into the head 15, directed through a conical central opening in the washer 16 and the rubber washer 17 to the extent permitted by an opening in the insert 18. The arm 19 is turned so as to screw the cap 20 on to the body 21 of the head 15 and compress the rubber washer 17 to make a leakproof connection to the lamp 14. Pairs of jaws 54 and 55 are provided for gripping and holding the lamp 14 in proper relation to the head 15. The head 15 takes a path of movement which first causes the lamp 14 to be introduced into an oven 22, Fig. 4, in which it is subjected to a temperature of between 400 and 600‹C for between one and ten minutes to burn out the binder of the coating on the inner surface of the bulb 1 and cause the dissipation and extraction of the occluded gases from the lamp 14. These gases and the products of the burning of the binder are exhausted from the lamp by the flow of air from the exhaust head 15 through the tubes 9 and 9<SP>1</SP>. This treatment is terminated by the motion of the head 15 which carries the lamp 14 from the oven 22 and breaks the air connection. The lamp is then by further movement of the head 15 positioned in operative relation to apparatus for tipping-off the exhaust tube 9<SP>1</SP> comprising the burners 23 and 24, Fig. 5. Succeeding operations to the lamp 14 provide for the exhausting, activation of the barium carbonate coated cathodes 7, the flushing, the final exhausting, the filling and the tipping-off of the exhaust tube 9 in that order. Electrical connections for causing the heating and consequent activation of the coated cathodes are made through a wiping contact made by the leads 8 at both ends of the lamp 14 with the contact strips 25, Fig. 6. Before the activation of the cathodes is complete, the lamp 14 is flushed by the admission through the head 15 of a quantity of an inert gas, such as nitrogen, or final filling gas and/or a quantity of mercury and then reconnecting the head 15 to another exhaust line. Subsequent operations cause the introduction of a limited quantity of an ionizable gas, such as neon, and a quantity of mercury, by means connected to the lamp through the head 15. The lamp is then sealed-off by the burners 26 and 27. The turret and other mechanism for effecting the above operations is similar to that described in Specifications 607,766 and 543,079. A three-turret mechanism is described in which the greater portion of the heating treatment apparatus is separated from the exhausting and filling apparatus in order to reduce the injurious effect of heat on the rubber parts thereof.