| 摘要 |
1,139,074. Moulding pipes. NIPPON HUME PIPE CO. Ltd. 7 Feb., 1966 [8 Feb., 1965], No. 5182/66. Heading B5A. A concrete pipe is centrifugally cast by feeding alternately into a horizontal rotary mould relatively hard and relatively soft concrete mixes to form adjacent layers, so that during mould rotation substantially all the surplus water in the relatively soft layer or layers permeates the hard or dry ones. During the casting operation the direction of mould rotation may be changed at regular intervals. |
