Patent GB-697790-A (GB)
Title: Improvements in and relating to a method and apparatus for manufacturing electronic vacuum tubes and the like
IPC: H01J29/94
Filed: 1950-04-03
Abstract: 697,790. Making cathode ray tubes &c. EASTMAN KODAK CO. April 3, 1950 [April 2, 1949], No. 8251/50. Class 39(ii) In the manufacture of electronic vacuum tubes, such as cathode ray tubes, a plurality of units each carrying a tube are moved continuously along a path from which each unit is independently removable, each tube while on a unit being subjected to the following operations: exacuation during travel over the entire path, inductive heating during movement over a portion of the path, cathode heating during movement over a further portion of the path, and external heating during movement over a large portion of the path including the inductive heating and cathode heating portions. In one example the movable units comprise a train of coupledcars 23 each loaded with a single vacuum tube 30 and drawn by a locomotive car 22 along an endless track formed by a pair of parallel rails 16, 17, Fig. 1, with semi-circular end connections. An endless rack 18 located between the rails engages a motordriven spur wheel 58, Fig. 3 (not shown), mounted on the locomotive car 22 whereby, the latter is progressed along the track. A current-feed rail 19 is located inwardly of the track rail 16. Two sides and one end junction of the track are located be neath a long heating-oven 24 of inverted U-shaped section, leaving one end of the track exposed to provide access for loading the tubes on the cars as they arrive successively at a loading-station 28 prior to entering the oven, and allowing unloading to take place at a station 29 as the car emerges from the opposite end. The cars 23, Fig. 4, each comprise a box-like structure supported on four grooved wheels and carry an electric motor 69 driving, a mechanical vacuum pump 71, the shaft 81 of the vacuum pump being also coupled to drive the shaft 79 of a water pump 72. The motor 69 is fed through a contact 51 which slides over an external bus-bar 46. On the top plate 82 of the car a pair of rods 42 carry a supporting member 41 for a tube 30, Fig. 2, which is located with its exhausting-tube 80 within a socket 38 extending downwardly through the plate 82, the neck of the tube 30 being surrounded by high-frequency heating- coil 84 fed through conduits 83, 85 which also extend through the plate 82. The exhausting socket 38 is connected to a double solenoid-operated valve 86, Fig. 4, which operates initially to connect it through a pipe 87 to the mechanical vacuum pump 71 and at the same time shuts off its connection to the throat 103 of a diffusion pump 74. The diffusion pump, operating continuously, then discharges through a pipe 88 into a ballast tank 89, the by-pass pipe 91 between pipes 87, 88 being closed by another solenoid valve 92. At a stage when the pressure in the evacuated tube has reached a predetermined value the solenoid valve 86 is operated by the closure of a switch 129 which is tripped by a stop 130 in the track of the car, thereby closing the connection through pipe 87 to the mechanical pump and opening the path to the diffusion pump, and at the same time the solenoid valve 92 opens the pipe 91 to the mechanical pump which thus acts in series with the diffusion pump to produce a high vacuum. In the event of a leak occurring either within the tube 30 or the vacuum system, damage to the diffusion pump is prevented by a safety-device in the form of a bellows switch 90 which operates at a predetermined pressure gain and disconnects the tube from the diffusion pump 74, leaving it connected to the mechanical pump; at the same time the bellows switch opens a resistance-heater circuit for the diffusion pump, and an alarm bell is actuated. As an alternative to the locomotive unit 22 for hauling a train of cars 23 around the track, an intermittent feed may be provided by an hydraulic ram device comprising a bar 175, Figs. 1 and 9, which is mounted adjacent to the track and carries a series of spring-pivoted dogs 179, the extremities of the bar being offset and connected to the outer ends of piston rods 171, 172 working within opposite ends of a double-acting hydraulic cylinder 170. In one direction of movement the dogs 179 abut against the faces 185 of lugs 183 extending upwardly from the front corners of the cars 23 and index the train forwardly, but override the lugs in the other direction of movement. A bus bar 45 supplying current by way of contacts 49 to the cathode heater of each tube 30 is mounted adjacent to the track on vertical beams 25 which also carry the bus bar 46 associated with a sliding contact 51. feeding the pumpoperating motor and diffusion pump heater of each unit, while a bus bar 43 and associated contacts 47, 48 supply H.F. current over the conduits 83, 85 to the coil 84 surrounding the neck of the tube 30. The conduits 83, 85 also carry cooling water which they discharge through a pipe 102 leading to a gutter 21.