Patent GB-674459-A (GB)
Title: Improvements relating to automatic stem-making machines for electron discharge devices
IPC: H01J9/32
Filed: 1950-05-04
Abstract: 674,459. Stem-making machines for electron discharge devices. EDISON SWAN ELECTRIC CO., Ltd. May 4, 1950 [May 28, 1949], No. 11071/50. Class 39(ii) An automatic machine of the rotary turret type for making stems for electron discharge devices is provided with a detecting-device located in a position immediately following that in which leadin wires are loaded automatically into a holder and comprising a number of slidable pins 19, Fig. 2, normally positioned to close a corresponding number of parallel circuits which are opened when the pins are pushed inwardly by abutment with the ends of correctly positioned and sound lead-in wires 7, but when one or more leadin wires are missing, or are too short, or bent, the corresponding sliding-pin circuits of the detector remain closed and operate means for ejecting all the lead-in wires from the holders. Fig. 1 shows five of a series of stem holding heads 1a ... 1e mounted on the periphery of an intermittently rotated table 2, the lead-in wires 7 being loaded into a head while the latter is halted at station 3. The ends of the wires 7 project upwardly as shown, and at station 4 the lead-in detector is lowered on to the protruding ends. Ejecting apparatus located between station 4 and 5 comprises a blow line 8 arranged to blow ejected leads into a collector 9. The detecting apparatus 13, Fig. 2, is connected by a bracket 16 to the automatic lead-loading apparatus at station 3 so that they are lowered simultaneously by the same operating device. The detector comprises a cylindrical housing 17 of insulating material, such as hard rubber, provided with a series of bores or holes 18 disposed in a circle and extending parallel with the axis of the housing, in alignment with leadin wires 7 when the latter are positioned correctly in a head. Terminal plates 22, 21 on the upper and lower ends of the housing 17 are connected to a pair of line terminals 14, 15, and have apertures which register with the longitudinal bores 18, the apertures in the upper plate 22 being large enough for the pins 19 to pass through with a close sliding fit, while those in the lower plate 21 are dimensioned to prevent passage of the pins, which are urged downwardly by helical springs 20 within the bores 18. The pins 19 thus provide a normal short circuit across the terminals 14, 15. A second housing 24 located below the terminal plate 21 is bored to receive a series of actuating rods 23 of insulating material which register with holes of smaller diameter in the bottom of the housing, whereby the rods 23 are prevented from dropping through. The undersides of these holes are countersunk to guide the ends of the lead-in wires into abutment with the lower ends of the rods 23. The arrangement may be modified by omitting the housing 24 and its actuating rods so that the ends of the lead-in wires 7 act more directly on the pins 19, insulators being provided to prevent the wires 7 from making electrical connection between the pins 19 and lower plate 21. The control system, indicated diagrammatically in Fig. 4, comprises a cam 26 geared to the mechanism for advancing the turret and timed to lower the loading and detector devices simultaneously at stations 3 and 4 respectively after the turret has made a forward movement and, immediately after, a cam 27 on the shaft of cam 26 closes momentarily a contactor 28. If, due to a faulty lead-in wire or wires, all of the pins 19 have not been displaced, a relay coil 29 is energized and closes holding contact 31 over a contactor 32 controlled by a cam 33, and at the same time a solenoid 35 is energized through a contactor 34. A lead-in wire ejector device is provided under each stem holder 1 of the rotary table 2 and, if the lead-detecting apparatus has been operated to energize the solenoid 35, an air valve 42 is opened by the solenoid and admits air to a servo-cylinder 43 which has its piston coupled to a cam surface in the form of a hump 41 that is slidable relative to a stationary annular track 40 located below the path of the work holders. The hump 41 is thus brought into the path of a roller 39 mounted on the lower end of a slidable ejecting plunger 36 which is disposed in the central axis of the head that has caused the ejecting action, the plunger being lifted vertically so that its upper end pushes the pins 7 out of the holder. The ejected wires are blown into a collector 9 by a jet of air from a nozzle 8. At the next assembly station 5 a cylindrical glass sleeve 10 is positioned automatically around the lead-in wires in the holder, and at station 6 a glass detector 6a comprising a pivoted feeler lever 6b indicates whether or not the glass sleeve has been placed in position. The glass detector also controls a lead-in wire ejection apparatus which ejects the wires when a glass sleeve is absent, the removal of the wires being assisted by a blast from an air nozzle 11. The glass detector and its associated wire-ejecting device may be omitted.