COIL FORM

1,160,053. Transformers. RADIO CORPORATION OF AMERICA. 19 Jan., 1968 [19 Jan., 1967], No. 3053/68. Heading H1T. The two coils 43, 44 of a transformer are wound on separate tubular members 11, 17 of resilient material, e.g. polypropelene and the inner of these members 11, is arranged to telescope within the outer member 17, a wedgeshaped projection 30 on the inner member, which projects into window 22 in the outer member, restricting the relative axial and rotational movement of the two members. Fig. 3 is a section taken immediately below projection 30. The portion 31 of the inner member just below the projection 30 is of reduced thickness and channels 32, 33 extend on either side of this portion and of the projection, thus enabling the latter to flex inwardly during the initial assembly of the two members. Axially-extending ridges 38 on the inner members run in corresponding depressions 39 in the outer member, permitting free axial motion but enabling the two members to be temporarily locked together by rotating one with respect to the other so that the ridges and depressions no longer coincide. The projection and ridges 38 may alternatively be on the outer member, with the window and the depressions on the inner member. Further ridges 35 on the inner surfaces of the members grip self-tapping threaded tuning slugs. The coils are wound in moulded spiral grooves (18, Fig. 1, not shown) and moulded projections (19) hold the coil ends, which are connected to terminals 13-16 on base 12. The transformer is enclosed in shield can 41 through which the upper part projects, and portion 20 of the outer member is roughened so that it can be gripped easily during adjustment of its position. The two members may be permanently interlocked by inserting adhesive or bonding material into a small aperture (21) in the outer member, or by passing the tip of a hot soldering iron through both the members.