Patent GB-823774-A (GB)
Title: Improvements in or relating to processes and apparatus for the manufacture of concrete articles, particularly of reinforced concrete
IPC: B28B23/06
Filed: 1956-02-07
Abstract: 823,774. Moulding concrete articles. INDUSTRIAL DEVELOPMENT CO. ESTABLISHMENT. Feb. 7, 1956 [Feb. 9, 1955], No. 3744/56. Class 87(2). [Also in Group XXX] Concrete articles are moulded with at least one cavity open to the outside from which the mass of concrete is permeated before it has set by a gas which causes superfluous water to transude and to be expelled from the mass of concrete, which is there compacted. An article such as a reinforced concrete railway sleeper (see Group XXX) is cast in two stages, first the tie member 1, Fig. 5, then the end members 3 in which are holes 32 for the rail holding-down screws. The tie member 1 is tubular and is cast in a mould 5, Fig. 1. The mould is in three parts, Fig. 2, each of which comprises sections 18 held together by bolts 35 with shims 21 between them to form narrow passages 19 which communicate with ducts 20. One part, 5a, is fixed and the other two are hinged to it at 14. The mould is closed by tightening a nut 17 on a screw 15. The reinforcement is first assembled, comprising longitudinal rods 2 surrounded by a helix 30 in a jute cover 31, and placed in the open mould 5 resting on its lower shoulder 22 which is notched to accommodate the rods 2. A jack 8, operated e.g. by compressed air, then raises a perforated tube 25 and with it a plug 12 of rubber or leather, the tube entering the mould and the plug closing the bottom thereof. Surrounding the tube 25 is another tube 24 of rubber or other flexible material, which is porous or perforated. Concrete is then poured into the mould through the top opening 7, a vibrator 29 is operated and a rubber plug 13 lowered by a jack 9 to close the top of the mould, fitting over a cap 27 on the top end of the tube 25. Compressed air is then admitted to this pipe and expands the tube 24, to mould the inside of the tie member 1, air passing through it and through the concrete and carrying away superfluous water through the narrow passages 19 and ducts 20. The reinforcement, including the sleeve 31, is embedded in the concrete. The plugs 13, 12 are raised and lowered, the mould is opened and the cast tie member is placed in a machine, Fig. 7, for casting on the end members. Each mould for this purpose is comprised in a shell 36, the end walls of which mould the ends 39, 40. The sides are moulded by porous sheets 48 stretched across perforated plates 49, Fig. 9. Threaded cores 41, adapted to mould the screw holes 32, pass through the bottom 37 and hold down the lid 42 by means of a nut 43. The cover comprises a series of sectors in the form of a tube and spaced from one another by short distances. The openings 51 through which the tie member 1 passes are closed by plates 52. The moulds and partly moulded sleeper are resiliently mounted on a cradle 54 which is raised and lowered by jacks 57 and rotated about trunnions 55 through a rack and sector 60, 61 by a jack 59. The lids 42 are raised and lowered by a jack 62 acting through a cable 63. For the moulding process the cradle is held down on supports 67 by the jacks 57, the concrete is poured in and the lids are lowered and secured by the nuts 43. A vibrator 64 is operated and compressed air is forced through inlets 50 and passes through the plates 49 to press the sheets 48 against the concrete, at the same time passing through the sheets and through the concrete and through the passages formed between the sectors of the cores and out through the ducts in the cores, carrying with it superfluous water. The moulds are opened and the cradle rotated by the jack 59 through 180 degrees and lowered by the jacks 57 on a removable platform 66. The cores 41 are unscrewed and the cradle 54 raised by the jacks 57, leaving the cast sleeper on the platform 66 to be taken away.