Patent GB-1319799-A (GB)
Title: Method for the manufacture of porous bodies
IPC: B22D7/10
Filed: 1970-12-30
Abstract: 1319799 Making porous bodies H J DAUSSAN 30 Dec 1970 [13 Aug 1970] 61858/70 Heading B5A A refractory and/or exothermic hollow porous body 1 (Fig. 17) is formed by applying at least one layer of slurry to a core 10 that is rotating about its longitudinal axis, the interior of the core being subjected to suction to filter off the dispersing phase of the slurry. The slurry dry material comprises: 1-35% of fibrous refractory material such as asbestos, rock-wool or glass; 1-20% of fibrous organic material such as paper pulp or sawdust; 45-90% of refractory or semi-refractory mineral material such as silica, magnesia, diatomaceous earth, verniculite, or pearlite; 1-50% of natural, organic or synthetic binder such as anylaceous substances, phenolic resins, or silicate of potassium, sodium, or refractory or magnesia cement. The porous bodies 1 may be used in foundry work. The core, and porous body removal.-The core 10 (Fig. 17) (see also Fig. 1, not reproduced) comprises a filter 17 of wire gauze, perforated sheet metal or wide-mesh filter cloth, which is shaped to define the internal surface configuration of the porous body 1, and is supported by end plates 111, 12. The filter interior communicates with a suction pump via pipes 13, 122 and and 20 a rotary seal 19, and the core 10 is disconnectible by releasing a catch 121. The porous body 1 is freed for extraction by removing plate 12 and either sliding the body 1 off the filter 17, or depressing a lever 118 to free a catch 116; a spring 115 then urges an annular ejector 113 and the body 1 to the right. Core immersion in slurry tanks.-In a first series of embodiments, the core 10 (Fig. 2) is immersed in a slurry tank B 1  by pivoting an articulation 27 of the knuckle-joint type. The core 10 is lowered until its end plates 11, 12 contact a pair of drums 22, 24. Drum 22 is driven by a motor 23 to rotate at a speed of about 15 r.p.m., the core 10 and drum 24, and to agitate the slurry by attached paddles (not shown). The interior of the core 10 is subjected to air suction giving a negative pressure of (0À2-0À6) bar, by a lift-and-force water of vacuum pump 29. Slurry deposition on the core 10 is continued until the layer is level with the end plates 11, 12, whereafter the core 10 is raised from the tank B 1  (see Fig. 3, not reproduced) and the deposited porous body dried sufficiently for removal, by continued air suction. For a porous body comprising a number of layers deposited from different slurries, the layers are built up successively in tanks B 1 , B, B 3  by pivoting the air pipe 20. The distance and angle between the drums 22, 24 is adjustable by bearings 25. In an alternative embodiment (see Fig. 5) the slurry tanks include a metallic grid 45 and a layer 46 of felt impervious to slurry but permeable to air. The slurry is agitated by compressed air G. The core 10 is supported in the tank by a friction cone coupling 42 engageable by a lever 44 and is rotated by a motor 43 through a system of hermetically sealed pulleys, pinions or chain and sprocket wheels. The deposited surface is finally smoothed by contact with a rotating, endless belt (48) (see Figs. 7, 4, not reproduced), which may be profiled to mould the surface. In a further embodiment (see Figs. 9, 10, not reproduced) the core (10) is supported with its longitudinal axis vertical by a pipe (60) that is adjustable vertically by a jacket (63) and horizontally by a carriage (61). The pipe (60) supports a plate (65) that contacts a motordriven drum (74) for rotating the core (10). The slurry is agitated by air from a calibrated valve (67) in the tank base (71), the valve (67) lifting when air pressure reaches a predetermined value. After deposition, the core (10) is raised so that the porous body contacts the drum (74) and a second, rolling drum (76), for smoothing the body surface. A plurality of layers may be built up by moving the core (10) between slurry tanks (B 1 ), (B 2 )...., by the carriage (61). Slurry distributers.-In a second series of embodiments, the slurries are deposited in a plurality of compartments of a distributer 201 (Fig. 11), having variable opening valves or volumetric feed regulators 215 at their bases. The compartments may be disposed side-byside to give layers of slurry juxtaposed along the length of the core 10, or end-to-end to give superposed layers. The core 10 is moved into contact with an endless belt 225, and a roller 224 is adjusted to give large belt/core contact. The distributer 201 is filled with slurries, the belt 225 driven, and core suction applied. The slurries are fed on to the belt 225 to be rolled on to the core 10, and belt drive and suction are continued after the distributer 201 has been emptied, to dry and smooth the porous body. In an alternative embodiment, (see Figs. 13, 14, not reproduced) the belt 225 is replaced by a thin, steel sheet trough (231) which is adjusted in curvature to touch two thirds of the core 10 surface, and the core 10 is rotated by motor, a crank handle (234), or by opposing rollers (242), (244) (see Figs. 15, 16, not reproduced). Slurry is deposited on the trough (231). The core end plates 11, 12 are constructed of a hard material, to prevent wear and so give a more accurate thickness of body. Rollers.-The external surface of the porous body may be contoured by shaped rollers (see Figs. 18-21), not reproduced) that are spring- urged towards one another.