1,205,075. Edge-filters. VACCO INDUSTRIES. 30 Nov., 1967 [1 Dec., 1966], No. 53134/67. Headings BID and B1T. [Also in Division B8] In an edge-type filter of the kind comprising sheet metal material wound in a coil 28, the sheet having protrusions (e.g. 74) on one surface to space the convolutions, the protrusions are of such shape as to present a tortous path for fluid particles tending to trap them; and means are provided for holding the inner and outer ends of the coil in fixed relation, on a hub 26, the coil edges being clamped by rings 38 in a two-part housing 10, 11. As described, the protrusions are formed by means of coining rollers. The coil 28 is wound on a hub 26 and enclosed in telescoping male and female members 27, 29 inside a housing 10, 11 having inlet 21 and outlet 22. To prevent radial movement of the coil convolutions, the ribbon edges may be provided with pointed projections (82, 84), Fig. 9 (not shown) which engage plastics strips on the inner surfaces of radial arms 32, 38 of the members 27, 29. The outer end of the coil is secured in non-radial slots 43, 47 in flanges 34, 40 of the members 27, 29 and the inner end in a slot in the hub terminating in a blind hole (45), containing a pin (48), (Fig. 3, not shown) see also Division B8. The coil 28 may be cleaned sonically.