Patent GB-829911-A (GB)
Title: Improvements in and relating to apparatus for making electron tubes
IPC: H01J5/24
Filed: 1956-10-08
Abstract: 829,911. Making electron discharge tubes. SYLVANIA ELECTRIC PRODUCTS Inc. Oct. 8, 1956 [ Dec. 16, 1955], No. 30662/56. Class 39(2) Apparatus for use in the manufacture of electron discharge tubes comprises a preheater including means to assemble bulbs and the stem-mounts to which the bulbs are to be sealed and to heat the bulb and stem-mount assemblies and transfer means adapted to transfer the heated bulb and stem-mount assemblies from the preheater to a sealing machine where the seal between the bulb and stem-mount is effected. The preheater and the sealing machine are indexed in synchronism, the movements of the transfer means being timed accordingly. As shown in Figs. 1a, 1b and 4 the preheater comprises two endlesschain conveyers 10 and 12 running in horizontal planes one above the other, the upper conveyer 10 being provided with a succession of holders 48 for resiliently retaining a glass bulb 14 by gripping its exhausting tube 16, and the lower conveyer 12 providing a mounting for a succession of posts 66 in vertical alignment with the holders 48, each to support a glass stem 18 with a mount 20 and mica spacing discs 19. The chain-conveyers 10 and 12 run in grooved tracks 40 and 42 respectively, Fig. 4, supported by a long horizontal table 30 carrying webbed vertical supports 32 for the upper track 42. At the loading station 21, Fig. 1a, the tracks are shaped so that the chains and their associated work holders are guided out of vertical alignment to facilitate manual loading by an operator who places the lead-in pins of a mount within a circular groove in a peg 68, Fig. 6, formed at the upper end of a post 66 carried by the lower conveyer, and also passes the exhausting tube 16 on to a seating between a pair of spring-pressed balls 56, Fig. 5, in a holder 48 on the upper conveyer, the tube 16 being thus gripped near to its junction with the bulb 14, which is held with its open end directed downwardly. From the loading station the assembly is indexed towards the left to a pusher button station 22, and during the indexing movements the bulb and stem are brought into correct axial alignment prior to the bulb being pushed downwardly to bring it into position around the mount 20. The downward movement of the bulb relative to the mount is made possible by the exhausting tube 16 sliding through the gripping means in the holder 48, the initial and subsequent positions both being shown in Fig. 7, which also shows the pusher station. At the pusher station a vertically reciprocating carriage 92 arranged transversely to the conveyers is slidable upon two posts 94 carried by a bracket mounted on the table 30. The carriage 92, which consists of a cross-bar 98 supporting two vertical legs 100, one on each side of the lower conveyer, provides a mounting for two rotary shafts 102 arranged parallel with the legs 100 and each provided with gear wheels 104, 105 respectively at their upper and lower ends within gear boxes 106,107. The upper gears each mesh with a separate rack bar 108, one rack bar being behind one gear and the other rack bar being in front of the other gear, so that simultaneous rotation of the shafts 102 in thesame direction produces movement of the rack bars in opposite directions, thus. effecting an opening and closing of halfconical guide jaws 116 mounted on the inner ends of the rack bars. The jaws areurged resiliently together by a spring 119 located below the lower cross bar 98 and connected at one end to a fixed pin 120 on the carriage 92, and at the other end to a pin 121 secured on the end of a horizontal rack bar 122 mounted slidably in the lower gear boxes 107 and in engagement with the gears 105. Timed opening of the jaws- 116 to permit indexing of the bulbs is effected by leftward movement of the bar 122 when its end 124 is engaged by a lever 126 actuated by a cam 129. The opening of the jaws 116 coincides with indexing movement of the conveyers and upward movement of the carriage 92. Movement of the carriage 92 is effected by a cam 130 provided with a contoured side face for a follower on a lever 134 which is connected by a link 136 to the lower portion of the carriage and produces rapid vertical reciprocation thereof. A vertical thrust rod 138 which moves with the carriage and is also slidable within bearings therein is pressed downwardly against the long arm 1'40 of a bell-crank by an encircling spring 142 located between a stop 144, secured on the rod, and an upper portion of the carriage, the stop acting also to prevent rotation of the thrust rod so that a lateral pusher finger 148 at its upper end' is aligned with the upper end of the exhausting tube 16 of a bulb at that station. The short arm of the bell-crank 140 is engaged by a lever arm 152 which is controlled by a cam 150 on the shaft 86 of cams 129 and 130, the arrangement of the cams being such that after the jaws 116 have closed on the bulb 14 the long arm 140 of the bell-crank is allowed to drop, whereupon spring 142 forces the rod 138 downwardly so that the finger 148 presses down on the exhausting tube 16 and thrusts the bulb between the jaws 116 on to an internal shoulder 118 provided on them, the jaws spreading as necessary due to the pressure on their conical inner walls. With the bulb thrust down on its seat or shoulder 118 the carriage 92 and thrust rod 138 are moved down together by the linkage 136 and lever 134, so that thebulb, guided by the mica discs 19, slides over the mount 20 to the position shown at the right of Fig. 7. The assembled bulb and stem mount are next indexed through a long pre-heating chamber formed by a pair of box-like bodies 24, 25 disposed respectively at opposite sides of the path of the bulb assembly and filled with heat insulating material 36, the adjacent faces of each of the boxes being formed with a longitudinal recess to accommodate a conventional helically coiled electric heater 23. Preferably the heaters extend substantially to the unloading station 26, Fig. 1b, where a transfer device removes a bulb and stem mount assembly from the conveyer and transfers it to 'the adjacent sealing machine 28. The transfer device comprises a pair of jaws 160, 162, Figs. 12 and 13, carried by supports 204, 206 mounted on a pair of bars 200, 202, which are slidable in opposite directions within a slot 198 in a carriage 196 which is slidable longitudinally upon a pair of parallel bars 192, 194, the opening and closing of the jaws being effected by rotation of a pinion 190 in engagement with rack portions 201, 203 on the bars 198 carrying the jaws, whereby the latter are moved in opposite directions. The pinion 190 is in the form of a horizontal rod provided with teeth extending throughout its length, so that when the carriage 196 is moved along its supporting rods 192, 194 the rack teeth 201, 203 on the bars 198 retain a driving engagement. Oscillatory rotation is imparted to the pinion 190 by a vertical rack bar 186 which is reciprocated vertically within, and relative to, a sleeve 168, Fig. 10. The lower end of the rack bar 186 carries a laterally supported roller which is engaged within the forked end of a rocking lever 180 on a shaft 90 the lever being operated by a cam 178 on the shaft 86. The jaws 160, 162 comprise three vertically spaced pairs of holding means for the bulb assembly, viz. an upper pair 208 which grip an exhaust tube, an intermediate pair 210 contoured to grip the bulb, and a lower pair 212 formed with an internal groove to engage the periphery of the stem disc 18. The frame 164 carrying the jaws is provided with a collar 166, Fig. 10, pinned to the sleeve 168 which is reciprocated vertically by a cam-operated lever 174 connected to the lower end of the sleeve and operated by a cam 176 on the shaft 86. Sliding movement of the carriage 196 along its horizontal supporting rods 192, 194 is effected at timed intervals to transfer a gripped bulb assembly to the sealing machine by means of a further cam 218, Fig. 1b, on the shaft 86, this cam acting through a bell-crank lever 220 mounted on a shaft 90, a link 222, an arm 224 fixed to a shaft 228 having at its upper end an arm 232 connected by a link 234 to the carriage 196.