Patent GB-763310-A (GB)
Title: Improvements in or relating to the manufacture of electric incandescent lamps
IPC: A01D57/04
Filed: 1954-10-01
Abstract: 763,310. Making electric lamps. WESTINGHOUSE ELECTRIC INTERNATIONAL CO. Oct. 1, 1954 [Oct. 9, 1953], No. 28326/54. Class 39(2) Electric incandescent lamp bulbs are coated electrostatically in a machine comprising a conveyer carrying a series of rotating bulb-receiving heads which are indexed. through successive work stations including means for heating. the bulbs, to render them electrically conductive, electrostatic dry-spraying mechanism which coats the bulbs internally, . and a lehr for heat-treating the coated bulbs to remove substantially all free moisture therefrom. The spraying mechanism comprises at least a smoke generator, a smoke-expansion chamber, and a reciprocating smoke injector nozzle assembly A steam injector unit is also provided for steaming the bulbs subsequent to the application of the coating, the unit including a steam generator and a reciprocating steam injector nozzle. The conveyer comprises a series of flanged rings 136, Fig. 3, connected together at opposite ends of a diameter by hinge pins to form a chain, each ring carrying an inner indexing-roller 259, Fig. 1, positioned to engage the edge of a rotary cam disc (not shown) whereby the chain is indexed around the periphery of a substantially oval table 12, an outer roller 258 being also provided on each ring 136 to ride upon a guide rail to ensure proper horiontal alignment at the respective work stations. A cylindrical bush 134 within each ring 136 provides a bearing for a rotatable inner sleeve 130 which has a pulley 132 secured at its lower end. and an upper flange supporting the flange 140 of a hollow bulb chuck 138 made of insulating lava and secured in position by pins 139. The upper part of chuck 138 is contoured to fit within the neck of a bulb 50. These assembled parts form a head 30 which can be rotated by an external endless driving belt 32 engaging the pulley 132, there being nineteen such heads around the table 12 and nineteen positions or stations at which the convever is halted the rotation of the heads while at the loading station 1 and unloading station 19 being prevented by taking the driving belt around guide pulleys 36. Loading may be effected automatically by an arm 38 which is oscillated to-and-fro between the coating-machine and an adjacent feeding unit 11 of a mount sealing machine, a second arm 96 operating in synchronism with the arm 38 being arranged to transfer the coated bulbs from the coating machine back to the unit 11. A head which receives an inverted bulb at station 1 commences to rotate at station 2, and at this station and station 3 the bulb is preheated by a stationary preheater 56. Also. while at station 3. an air blower and drier 58 removes dust and moisture from the bulb. Between stations 4 and 5 a detector 60 ascertains whether or not the head 30 is empty and, in the latter event, prevents the first dry silica spraying of the interior of the lamp bulb that occurs normally at station 5. Stations 5 'and 7 are provided with gas and .air burners 292 or radiant type heaters, for heating the bulb to approximately 100‹C. to render it conducting and, also at these stations, air blast tube cleaners 62, 66 for cleaning the tubes through which silica powder has been injected into the bulbs. A second bulb detector is positioned between stations 6 and 7 to prevent, in the absence of a bulb, the second dry spraying normally applied at station 7. From stations 8 to 13 external air blast cooling is applied through delivery pipes 374 radiating from a central manifold 370 which is fed with cool high-pressure air at its lower end, the object being to enhance the condensation of steam injected into the bulbs by a unit 79 at stations 12 and 13, where the now coated bulb is given two successive steamings to improve the adherence of the silica coating. From stations 15 to 18 the coated bulbs are lehred within a hood 92 by burners 94 connected to a manifold 460 into which gas and air are supplied, the bulbs being heated to a temperature of at leas 450‹C. In addition the bulbs are flushed internally while at stations 14 to 18, by either hot air or nitrogen fed upwardly into the heads 30 from delivery lines 450 supplied from a manifold 440 and preheated to at least 250‹C. At station 19 the bulbs pass to the loading turret of the sealing machine at which they are sealed to a lamp mount while still hot, and then exhausted. The bulb detectors 60 and 64 mounted between stations 4. 5, and 6, 7 respectively, comprise pivoted feeler arms 160, and 102, (the former being shown in Fig. 16) which are struck by a bulb 50 during its indexing movement and close a switch 164 in the timing circuit of the machine thereby energizing a time delay relay 166 which permits the silica smoke injector assembly '165, Fig. 3, of the first silica spraying unit to position itself within the chuck 138 of a bulb-holding head 30 at station 5. A second time delay relay 167 in the timing circuit controls the energization of a solenoid 168, Figs. 2 and 16, and hence the closing of a butterfly valve 169 in the silica-smoke producing-units 62 and 66, and the opening of a solenoid-operated air valve 175 in an air supply line 174 of a smoke generator 170. The smoke generators, which are identical, may comprise a glass or vitreous container 170 with a cap or cover 173 sealed at its upper end and connected to a supply pipe 180 for powdered silica 176. The air supply line 174 projecting through the bottom of the container 170 projects above the level of the silica powder and carries a series of downwardly inclined jets 178, so that high pressure air admitted through the supply line forces the silica upwardly through an inclined delivery line 184 connected to the cap 173 and extending almost to the top of an expansion chamber 190. The expansion chamber has an outlet pipe 210 extending downwardly therefrom and connected by a flexible tube.212 to the smoke injector nozzle assembly 165, Fig. 3. The swirling turbulent flow of silica powder within the chamber 190 causes the undesirable heavier particles to fall downwardly into a return line 198 extending from the bottom of the chamber into the smoke generator cap 173, from where they. are re-agitated and broken up. A solenoid operated butterfly valve 169 in the return line 198 is normally closed during coating. Similar smoke injectors provided at stations 5 and 7 are carried on the respective limbs of a substantially V-shaped bridge which is, reciprocable vertically upon guide rods 226. by a cam-operated linkage. A coating tube 262 extending axially within an outer sleeve 250 is connected at its lower end to the flexible tube 212 of the powder supply line, and at its upper end carries a flanged coating nozzle 280, Fig. 3, provided with a probe 284 surrounded by a series of parallel outlet holes 282. The probe 284 serves as the negative pole of a high frequency, high voltage circuit. The sleeve 250 surrounding the coating tube 262 has a lower portion 254 made of metal, and an upper portion 252 of reduced diameter and of insulating material, such as a plastic. A conductor 286, Fig. 1, connects the coating tube 262 and probe 284 to the negative side of a high-frequency high-tension generator 288, the positive side of which is connected to one of the burners 292 of the heater 70 mounted adjacent to the stations 5 and 7. The bulb has previously been made conducting by heating to a temperature of about 100‹C. by the preheater 56 and heater 70, and the application of a voltage varying from 15 to 25 K.V. applied between the probe and the conducting glass causes the charged silica particles to drift to the bulb wall with a force dependent upon the applied voltage. An alternative form of silica smoke producing unit, Fig. 14, (not shown) embodies a silica powder reservoir or supply tank into which the powder is fed from an inverted bag at its upper end, and the powder within the tank is agitated by a paddle at the lower end of a vertical shaft. At the .end of the coating or .spraying period, as determined by the relay 167, the butterfly valve solenoid 168 and the air pressure solenoid 177 are de-energized, whereby the butterfly valve 169 is opened to permit the agglomerate of silica powder particles to be returned to the smoke generator 170, and the air valve 175 in the air supply line 174 is closed. Air blast powder tube cleaners. These are mounted adjacent to a head at stations 5 and 7. and operate to clean out the nozzles 280 and adjacent parts of the nozzle assemblies during the indexing of a head 30 from stations 5 to 6 and stations 7 to 8. Each of the, cleaners 68 comprises an arm 350, Figs. 11 and 12, mounted on a stationary support above the conveyer, on a shaft 352 surrounded by a torsion spring 354 tending to swing the arm 350 inwardly towards the nozzle 280 of the heads 30. The free outer ends 353 of the arms 350 are substantially annular in shape and carry an air blast tube 356 extending radially from the periphery thereof into a central air blast cleaner hole 358, the other end of the tube 356 being connected to a source of high pressure air controlled by a solenoid operated valve actuated at the required times. When head 30 arrives at the first coating station 5 the air cleaner 68 is held in an inoperative position by the arm 350 bearing against the lower flange of the pulley 132 carried by that head. After the coating operation and during the indening of the head to station 6, the pulley is disengaged from the spring-biased arm 350, so that the latter swings inwardly to bring its central hole 358 above a hole 360 in the table 12 at station 5 and above the silica injector nozzle at that station. A short blast of high pressure air is then released to clear the nozzle 280, the coating tube 262, and upper portion of the sleeve 250 of the nozzle assembly. A similar series of operations takes place at station 7. The cooling mech