Patent GB-808482-A (GB)
Title: Improvements in methods of and apparatus for assembling electronic tube components or the like
IPC: H01J9/00
Filed: 1955-01-27
Abstract: 808,482. Making thermionic valves. SYLVANIA ELECTRIC PRODUCTS Inc. Jan. 27, 1955 [Jan. 29, 1954], No. 2556/55. Class 39(2) [Also in Group XL(a)] A multiple-station valve-making machine operates upon a stem having a number of parallel projecting wires upon which a mica spacer is first assembled and utilizes the principle of employing certain of the wires as "reference wires" which are engaged at the various stations by tools which use them to orient the mica disc or other tube components in exact positions for assembly of further components. As particularly described the valve is a pentode in which the suppressor grid is reduced to two parallel wires and it is these wires which are used as reference wires. General summary of operation. The machine consists of an elongated bed 11, the left and right halves of which are shown in Figs. 1A, 1B respectively, around which the stem is carried by a conveyer consisting of large links 12, 12a moved by sprockets 14, 16 at each end. This conveyer forms the subject-matter of Specification 808,483, but may be omitted and replaced by manual loading and unloading at each station. Each third link 12a has a stem block 10 and these blocks are indexed successively from Station A to Station L where operations are performed on them while they are secured clamped. All operative parts are ultimately driven by the central drive 20 which, by bevel gears, drives transverse shafts 23 providing power for each station. At Station A, the stem h with nine equal length wires 1 . . . 9 is loaded into the stem block in a standard position by a transfer machine which forms the subject-matter of Specification 808,484 At Station B. the wires are trimmed to provide short wires 2, 8, 9 and intermediate-length wires 1, 3, 4, 5, the wires 6, 7 being left as reference wires. At Station C, wires 1, 4 are swaged to provide additional abutments s for the first mica disc. At Station D, the first mica disc bm is pierced and mounted in an intermediate position on wires 6, 7 and some short wires are bent out cf the way of the grid wires. At Station E, inner grid g<SP>1</SP> is monuted on the mica disc and a stop gs is welded to a projecting grid wire. At Station F, the second grid g<SP>2</SP> is mounted on the mica disc and the whole assembly is pushed down to its final position abutting short wires 2, 8, 9 and abutments s. At Stations G, H anode parts a are mounted on intermediate wires 3, 4 and 1, 5 respectively. At Station I, top mica disc tm is pierced and pushed over reference wires 6, 7 and grid wires. At Stations J, K wire straps c are formed and inserted in the tops of anode parts a and the anode parts are welded to these and to wires 1, 3, 4, 5. At Station L, wires 6, 7 are trimmed and the assembly unloaded from the machine, for completion of the valve system by connecting the grids to stem wires and assembly of the cathode on wires 6, 7. Alternatively only a minimum number of welds may be made at Stations J. K, and the remainder completed after unloading: Stem blocks. These consist of two-part jaws 10i, 10j, Fig. 3,clamped together by wedges 10o pressed into channel grooves at the side. The jaws are opened when required by wedges 40c, Fig 5. pressing into grooves 10s at the back. The blocks are held loosely by spring-loaded bar 10c while travelling with the links 12f, but are rigidly clamped in exact positions at the stations by pins 36o, 36q. Wire-trimming (Station B). The wires are first combed from the stem outwards by a composite combing tool consisting of three parts 50, 52, 54, Fig. 15 which converge on the wires from three directions and finally hold them locked in position as shown in Fig. 16A. At the end of the outward stroke of the tool the wire ends are in the exact pattern to engage the holes 56a in a trimming die 56, Fig. 16, and the tool is then removed. The die is then pushed down towards the stem and towards the end of its stroke the stem block jaws 10i, 10j open momentarily to enable the stem to adjust itself and thus correct inaccuracies in the initial standard position. Cutters 58 then move in slots in the die to trim the wires to the desired length. Wire-swaging (Station C). Long leads 6, 7 and intermediate leads 1, 3, 4, 5 are again gathered and combed by a two-part tool 80, 82, Fig. 25, before swaging tools 88, 90, Fig. 26, operate upon leads 1 and 4 to form cruciform abutments. The combing tool contains an electric sensing finger 84 which disables the sequence of operations if its failure to engage long leads 6, 7 shows that no stem is present. Stem block jaws again open while the leads are being combed and swaged to give further correction to stem orientation. Bottom mica assembly (Station D). Here unpunched mica discs bm are manually loaded on to a table 112, Fig. 33, which indexes them beneath punching tool 120a, the descent of which not only punches the disc with the desired pattern of holes but pushes it into a hole in a transfer plate 124. Before going under the tool each disc is gauged at a previous station to ensure that it is not excessively thick or thin. The plate 124 is moved .through a quarter circle, Fig. 36. between the stem h and a pushing tool 126. Before the disc is pushed on to the wires 6, 7, these are correctly aligned by two sets of two-part combing tools 128, the first provided with triangular teeth and the second with conically bevelled apertures. At this station also the short leads 2, 8, 9 are bent slightly outwards from the plane of the grids by pushing in two blunt-pointed clearance tools. First grid assembly (Station E). The grids are fed forward by a jigging conveyer 140, Fig: 39, at end of which a swinging cradle 142 picks up the foremostgrid and swings it 90 degrees into position in front of the pusher 144. At the same time mechanism not shown forms a grid stop gs, Fig. 54 from strip stock. Interposed between the grid cradle and the stem is a two-part guide 150a, 150b, Fig. 54, consisting of two funnelled apertures 151h which fit over the reference wires 6, 7 and a channel 151j guiding the grid to the correct position relative to the holes in the mica. The sequence of operations is then that the grid stop held between welding jaws 148 is moved across and behind the mica bm, Fig. 50, the guide 150a, b fits on to the wires 6, 7, the pusher 144 pushes the grid g<SP>1</SP> into the channel of the guide until the grid wires project through the mica, one of them engaging the grid stop gs, Fig. 54, the stop is welded on and the parts return to their former positions. The pusher 144 has a stripping mechanism to prevent retention of a faulty grid when it is withdrawn. The welding jaws also act as a backing for the mica disc to maintain it in its half-way position on the wires 6, 7. Second grid assembly (Station F). This is generally similar in operation to Station E with the following modifications (a) the pusher 144<SP>1</SP>, Fig. 58, has a mandrel 164 which enters the first grid and ensures that the second grid g<SP>2</SP> slides down mandrel portion 164e in correct position over the first grid, (b) there is no grid stop mechanism but as the mica is in this operation pushed fully home over wires 1, 3, 4, 5, there is provided a backing plate 168, Fig. 61 for combing and guiding these wires into the mica (c) a preliminary alignment of the first grid by jaws 150 is necessary to ensure that the mandrel 164 enters the first grid (d) after the second grid is free from the mandrel its wires are guided into the mica by funnelled guide 166. A view of all the parts in an intermediate position is shown in Fig. 63. Anode assembly (Stations G, H). Here the anode parts a are pushed on to wires 3, 4 and 1, 5 respectively and the requisite combing and guiding tools consist of a central member 172u, Fig. 71, engaging wire 7 and side members 172a gripping wires 3, 4. A superimposed funnelled guide 172wb (only one side shown) guides the anode part on to the wires. Top mica assembly (Station I). The mica is punched as in Station D and transferred into a position for insertion over wires 6, 7 and grid wires of grids g<SP>1</SP>, g<SP>2</SP>. The necessary gathering tools consist of a first tool 176a, b, Fig. 78 which engages wires 6, 7 until the mica is inserted over them and then retracts and a second tool 178a, b which engages the grid rods while these enter the mica. Anode-connector application (Stations J, K). The anode connectors c are made from wire stock in the form of a hairpin with the top bent down so as to engage the top mica. A funnelled guide 188, Fig. 95, engages wires 6, 7 to align the connector legs with the holes in the top mica and guide tools 184 align the anode parts with these holes by reference to the second grid wires. Welds at top and bottom points of the anode are then made by a moveable welding tool. General operation. The moving parts at the various stations are operated generally by cams of appropriate profiles. Motion diagrams of all these cams and movements are given, Figs. 101 ... 110A, not shown. The connections between the stations and the operating spindles 23, Figs. 1A, 1B, have electrically operated clutches so that they can be disabled if the movements are not required to be performed in an indexing period.