Patent GB-233084-A (GB)
Title: Improvements in or relating to machines for coiling wire helices
IPC: H01J19/00
Filed: 1924-02-27
Abstract: 233,084. General Electric Co., Ltd., and Eden, C. G. Feb. 27, 1924. Electric fittings. - A machine for coiling wire helices in one or more support wires, the diameter or the combined diameters of which is or are less than the internal diameter of the helix, more especially for making grid electrodes for thermionic valves, comprises a rotatable mandrel, a fixed guide through which a support wire passes in proximity to and parallel with the mandrel, and a rotary carrier by which the wire is coiled. A spindle a rotated by gearing c, 30, from a shaft driven by an electric motor and enclosed in a fixed sleeve b carries a mandrel f, which projects through the end of the sleeve and is tapered to leave a space e through which a support wire i is passed by way of an opening h, the support wire then passing through a channel in the end of the sleeve alongside the mandrel. The end of the support wire is secured in a clamp u carried by a slide t which is traversed by a screw w rotated by the gear 30. On the sleeve b is rotatably mounted a disc k which carries a guide roller m and also a bush p on which is loosely mounted a reel o carrying the wire n, the reel being retained in position by a collar q provided with a guide eyelet r. The disc is rotated by gearing 33, 32 from a shaft 20 which is geared to the driving shaft. The end of the wire n is soldered or welded to the support wire and is then coiled thereon and round the mandrel by the rotation of the disc, the formed coils slipping or screwing off the mandrel, the pitch being determined by the slide t. The mandrel may be screw threaded. Some or all of the coils as made may be welded to the support wire by a tungsten contact carried by an arm x which is connected to one terminal of the secondary of a transformer x and is mounted on but insulated from a spindle y rocked by a spring- pressed lever 13 and cam 19 and traversed by a cam 14 against the action of a spring 15. In order that each coil may be welded to the support wire the primary circuit of the transformer is made once during each revolution of the disc k by a pin on an insulating disc 26 carried by the shaft 20, which wipes over a pair of strip contacts carried by rockable insulated blocks 21 normally held by springs in contact with stops 23. The electrode travels with the coil until the weld is made and then moves away therefrom and is returned to engage the next coil. In making grids with a given number of turns the welding current may be cut off at intervals so that a number of coils welded to the support may be interspaced with a number of loose coils which are subsequently removed by hand. To prevent the loose coils from binding around the support wire, the end of the mandrel may have a reduced and tapered extension. The mandrel and rotary wire carrier rotate in the same direction at substantially the same angular velocity, which, however, may be made slightly different so as to prevent wear of the mandrel due to the pressure exerted by the welding electrode. The pitch of the coils is varied by altering the rate of traverse of the slide, which may be variable so as to obtain helices of variable pitch, such as close at the ends and open in the centre. The welding may be effected by a roller electrode 34 carried by a spring-controlled pivoted arm 35 which is mounted on a disc 36 insulated from and movable with the disc k on which the reel o<1> is mounted. In a modification, the wire may be coiled on a pair of parallel rotary mandrels and support wires to each of which the coils are welded to obtain helices of elliptical cross-section.