Patent GB-1070451-A (GB)
Title: Screening apparatus
IPC: B01D29/01
Filed: 1965-02-18
Abstract: 1,070,451. Hollow stationary filters for liquids. CANADIAN INGERSOLL-RAND CO. Ltd., and BIRD MACHINE CO. Feb. 18, 1965 [April 29, 1964], No. 7147/65. Heading B1D. A mixture of fibrous material and liquid is introduced at 8, preferably tangentially, to an inlet gutter 6, whence it flows radially inwards over a baffle 10 to an annular zone between a fixed cylindrical perforate screening member 12 and an imperforate drum 24, rotating at preferably more than 3,000 feet per minute. Accepted material passing through screen 12 flows out, preferably tangentially at 16, the horizontal flow direction being the same as that of the incoming material. Rejected material from between the drum and screen flows out at 20, assisted if necessary by liquid introduced at 46 to the interior of drum 24 and flowing downwardly therefrom through an annular gap 48. The invention is characterised by the provision of bumps on (as shown), or indentations in, the surface of the drum 24; alternatively the invention may be embodied in apparatus where both the screen and the revolving member are disc-shaped and lie in parallel planes (see below). The projected area of each "offset portion", (the bumps or indentations), on a plane parallel to the base surface has a length to width ratio less than about five to one, and further, this area is at least substantially equal to the projected area of the impelling surface of the offset portion on a plane perpendicular to its direction of movement. As shown the drum 24 tapers upwardly, but it may be parallel-sided, Figs. 7 and 8 (not shown), in which case the screen 12 may taper downwardly, Fig. 7 (not shown). The bumps may be hemispheres; the indentations may be perforations in a cylindrical shell mounted on and in contact with the smooth surface of an inner drum-like support. The offset portions may be evenly-spaced in parallel vertical rows; the paths of the resulting horizontal rows overlap slightly at both edges. Where the portions take the form of indentations, the drum exterior may be provided with ribs (e.g. six in number) inclined at an angle to the vertical, Figs. 18, 19 (not shown). The offset portions may be formed by raised rectangles with rounded ends, and tops; alternatively they may be cones or cylinders; dents of these forms can also be used. In a further alternative, Fig. 14 (not shown), the offset portions are in the form of triangular tongues (56s) struck upwardly from a base cylinder, the raised parts trailing in the direction of movement; preferably the base cylinder is secured to an impervious support. Fig. 21 (not shown), is a modification of Fig. 1. The incoming mixture enters the top of the casing and impinges on the top of drum 24, which is provided with vanes for flinging it outward directly to the zone between drum and screen. The lower end of the drum forms a labyrinth seal with the bottom of the casing; water supplied thereto both lubricates the seal and dilutes the rejected material; vanes are provided on the drum at this location to propel the rejected material to its conduit. In Fig. 20 (not shown), the drum has a short central cylindrical portion, the remainder being two frusto-conical portions with their wider ends at the extremities. The surrounding perforate screen has a central inlet gutter with which the inlet communicates. An "accepts" conduit is provided opposite each screen portion and a "rejects" conduit at each end of the casing. In Fig. 22 (not shown) a rotary member in the form of an inverted cup depends into the space between concentric perforate screens from the bottom of which a "rejects" conduit extends. Feed and "accepts" arrangements are somewhat as in Fig. 1. In Fig. 24 (not shown), mixture is fed upwards through the centre of a flat annular screen above which rotates a disc with appropriate offset portions. "Rejects" are flung sideways and "accepts" descend through the screen. In Fig. 23 (not shown) a disc rotates between two horizontal annular screens. In all cases the rotary member provides pulsations; paper pulp may be treated.