Patent GB-1494208-A (GB)
Title: Method and apparatus for moulding cement
IPC: B28B23/00
Filed: 1974-11-25
Abstract: 1494208 Feeding cement into moulds TAISEI CORP and Y ITO 25 Nov 1974 [24 Nov 1973 14 March 1974 20 March 1974 23 July 1974 25 July 1974 9 Oct 1974] 51030/74 Heading B5A [Also in Divisions E1-E2] Hydraulic cement is introduced into a mould cavity having interstitial air spaces defined therein by the internal configuration of the cavity or by the presence of prepacked reinforcing material, the cavity being connected to a reservoir or including a reservoir for holding excess cement surplus to that initially required to fill the interstices. The cavity and reservoir are maintained at a pressure below atmospheric and less than that of the cement supply, until the cavity is filled with cement and excess is present in the reservoir, where after the pressure in the reservoir is increased to force some of the excess cement into the cavity. In a first embodiment (Fig. 3), coarse aggregate 2 is packed into a sealed mould cavity on top of a thin mortar layer 35. Air is removed from between the aggregate particles by a vacuum pump 42, which evacuates also closed supply and reservoir tanks 27/38. Mortar is introduced into tank 27 from an open supply tank 29, and the opening of valves V 1 /V 2  causes mortar to be slowly transferred into the mould cavity. After a time, a valve V 4  is opened in steps to apply atmospheric pressure to the supply tank 27 and so speed up mortar feed, which can be further increased by a pressure source 43. When excess mortar is seen, or detected by indicators 17/17a, in the reservoir 38, atmospheric pressure or pressure from source 43 is applied to the reservoir, to force some of the excess mortar back into the mould. The mortar feed pipe 26, covered with wire mesh, is left embedded in the mortar, and feed is switched between stacked moulds (not shown) using couplings 33/34. Moulding is aided by vibration, and the concrete is cured at 20‹ C. in wet air, or at 60‹ C. in steam. A tank 41 separates air and liquid. In a second series of embodiments (Fig. 28), using a mould 101 having its major walls disposed vertically, the mortar is fed from the supply tank 27 into one side of the upper end of the mould, while air and overflowing mortar leave from the opposite side into the reservoir tank 38. Alternatively, only the supply tank 27 is employed (see Fig. 30, not reproduced) arranged centrally of the mould top and also acts as a reservoir; the single tank 27 can be flanked by a pair of small overflow tanks (105), (Fig. 31, not reproduced) for removing oozed water, and air is evacuated from the mould via a tank (102) connected to the mould bottom. In a further modification, a reservoir tank 38 (Fig. 32) is positioned centrally at the top, and mortar sucked into the mould from an open tank 29 positioned at a lower level. The feed pipe 107 is pushed further into the mould as this fills, or the suction pressure is increased. In a third series of embodiments (Fig. 35), aggregate is packed between inner and outer frames 111, 112 and the cavities A and B are both subjected to reduced pressure. For a fourth embodiment (Fig. 36) the mould 120 is placed in a reduced pressure chamber 11. Mortar is fed into the mould from a closed supply tank 27 through a pipe 117, or is sucked directly from the open tank 29 into a funnel (123) (Fig. 37, not reproduced) that replaces the pipe 117. A second funnel is positioned as a reservoir to detect the overflow of mortar. The final opening of the mould interior to the atmosphere compacts the mortar. Pouring and de-airing.-Numerous examples are described, for introducing mortar into the mould. (a) Mortar is first sucked into the closed tank 27 (Fig. 3) from the open tank 29 (or run in from a highly positioned tank), before applying to the mould, so that tank 27 acts as a "cushion" to prevent separation of the mortar mixture. (b) The closed tank 27 is replaced by a U tube 50 (Fig. 5) or a vertically arranged cylinder. (c) A pump feeds between tanks 29 and 27, while the head of tank 27 is used to feed into the mould, or mortar is pumped into the mould from tank 27. (d) Tank 27 is replaced by bellows that expand and contract to keep the mortar pumping speed constant. (e) Mortar is sucked up into the mould from a lower positioned open tank 29. (f) Mortar is pumped into the mould, and simultaneously circulated back to the closed tank 27 via a valve or a further closed tank that operates if the mortar pressure increases too much. Excess air and water is removed from the mortar before casting, by pouring mortar into the closed tank 27 over a vibrated spreader 70 (Fig. 17), or through an inlet throttle valve.) Tank 27 is also vibrated, or replaced by a vibrated, inclined shoot. Overflow detection.-The exit end of the mould 1 (Fig. 22) includes a sand-filled cavity 80 which absorbs water oozing past a partition 77, and removed by a suction pipe 81. The partition gap 77 can include a plug of spongy resin. The outlet pipe 75 to overflow tank 38 is plugged with coarse aggregate 2a and enclosing wire mesh, to prevent loss of mortar from the mould end. The pipe 81 can include a transparent U-tube, a mortar detector, bellows, or a transparent coiled pipe. Material &c.-Plates, tubes, cylinders or rails are moulded from a mixture of cement, sand, coarse and fine aggregate (crushed stone), perlite, aluminium powder, dehydrating and dispersion agents and water. Steel bars or mesh, or metal/glass fibres are embedded. Application of this method is described for moulding foundations or roads, filling cracks, joining pillars, or underlaying pillars in situ (see Divisions E1-E2).