Patent GB-761971-A (GB)
Title: An improved method and device for the manufacture of concrete products by centrifugal means
Inventor: HEIDENSTAM ERIK JOHAN VON
IPC: B28B21/68
Filed: 1952-12-15
Abstract: 761,971. Centrifugal moulding of reinforced concrete pipes &c. AKTIEBOLAGET PRODUKTIONSMETODER. Dec. 15, 1952, No. 31757/52. Class 87(2). [Also in Groups X and XXVIII] Concrete or filling material or both are fed into a centrifuge drum by a conveying member that is connected to a movable core that shapes the interior surface of the hollow concrete article (pipe, mast, &c.) being made. The conveying member may be a tube and the movement of the core may be a sliding movement. The purpose of the filling material (as explained in Specification 735,864) is to keep up the internal pressure in the cast concrete and thus maintain the reinforcement stressed ; this material, which is granular material, e.g. ground ore or steel pellets, is removed when the concrete has sufficiently hardened. Fig. 1 shows a drum 1 which is rotated about a vertical axis 1c whilst a tripleconcentric-tube assembly 34a, 34b, 34c is raised. Through the outermost annular tube space A a partition layer 6 is fed and is applied to the interior of the drum by a core 40 ; through the intermediate tube space B concrete is fed and is applied to the partition layer by core 33 ; and filler 3 is fed through the central tube space C into the hollow concrete body formed by core 33. Longitudinal and circumferential steel wire reinforcement 8, 9 is supplied to the moulding space during the feeding of the concrete 2, the reinforcement 8 being wound on the inside of the reinforcement 9 or, as shown, on the outside. The pitch of the wound reinforcement may be small at the ends of the pipe and greater in the middle. The drum is spun to centrifuge the concrete, then the partition layer 6 is removed. This layer is made of paraffin wax, viscous oil or bituminous substance, preferably mixed with a filler, and is melted out after casting : or it may be of wet sand. The core 33 may be raised solely or partly by the vertical component V of the pressure N acting on the underside of the core during centrifuging. The wall of the drum may be hollow to receive a heating or cooling fluid, or may be fitted with pipes for this purpose, and by thus heating the drum the partition layer may be melted and removed through cock 48. Figs. 3 and 4 show a modified apparatus for making a tapered pipe or conical mast 2, the core consisting of relatively-movable overlapping portions 51 carrying standards 52 pivotally attached by links 53 to flanges 54 on the concrete-supplying tube 34a, to form a parallelogram. The links 53 carry rollers 56 which are pressed by centrifugal force against the inside of the drum, so that as the core moves upward it is held at a constant distance from the inside of the drum and the pipe wall has a constant thickness. A pre-cast stiffening ring 2b, Fig. 7, may be applied to the inside of the tapered pipe of Fig. 3, mortar 2c being applied as shown, filler 3 being filled in and the pipe again centrifuged. If the links do not form a parallelogram the thickness of the pipe wall may be so varied that the wall is thinner at the top than at the bottom. The apparatus may be disposed as a plant, Figs. 8 and 9 (not shown) having means for transporting freshly-made pipes through an annular steam-curing chamber. The pipe may be square in cross-section. Short pipes may be made by putting partition plates in the drum, Fig. 11 (not shown). In Figs. 12 and 13 the concrete 2 is supplied through a pipe 34 to a double-walled mould 33, 40 as the mould is raised, and an air-escape pipe 77 and reinforcement-holding means 72, 76 are provided. The partition layer 6 in this case is of filler material. The sliding mould or core may move vertically downward. The partition layer 6 may be sprayed on to the interior of the drum 1.