A method for vertical casting of pipes of concrete or a similar material in a mould system with a distributor wheel

Abstract: The invention concerns a machine for substantially vertical casting of pipes (8) of a concrete-material or a similar material and having a spigot end (11), comprising inner and outer mould parts (2, 12) for forming a space between the two mould parts, means for axially displacing the inner and outer mould parts with respect to each other during the casting process, an axially journalled distributor wheel (1) being rotatably mounted on the top of the inner mould part, said distributor wheel having a plurality of blades (4) for distributing the material in the space between the two mould parts. The object of the invention is to provide a machine of the above type, which, with much narrower longitudinal tolerances than known before, can repeatedly cast concrete pipes with spigot ends which have the desired full shape and a concrete quality which satisfies the made requirements with certainty. This object is achieved in that the machine additionally comprises at least one vibrator (19) being preferably arranged upwardly in the inner mould part, and in that a profile ring (16) is provided which is or can be arranged upwardly in the outer mould part to shape the spigot end of the pipe.

Description: The invention concerns a method according to the preamble of claim 1. Casting of e.g. concrete pipes generally takes place in mould systems of the type mentioned in claim 1 by filling fresh concrete from above down into the ring gap between the vertically positioned mould parts, the concrete being then vibration compressed, while the two mould parts are displaced with respect to each other. The simultaneously rotating distributor wheel on the top of the inner mould part is to serve to distribute the concrete uniformly and evenly in the ring gap, but since the relatively dry concrete, which is normally used for such purposes, is stiff and difficult to deform in a fresh non-vibrated state. DE-B-1 146 798 discloses a machine for vertical casting of pipes of concrete comprising inner and outer mould parts. The inner mould part is fixed in relation to the outer mould part and a distributor wheel is rotatably mounted on top of the inner mould part in such a way that vibrations generated from vibrators arranged in the inner mould part causes the distributor wheel to rotate. US-A-3,551,968 discloses a method for compacting concrete (packer-head) where an outer mould is gradually filled with concrete, which by the rotation of a packer-head, is compressed against the outer mould to form a pipe. A feeding device comprises a cone member where surplus concrete from the filling is deposited and withheld by a lower cylindrical part of the packer-head. It is hereby avoided that part of the surplus (excess) concrete is spilled during de-moulding. One object of the invention is to provide a method for casting pipes by use of a vibration process, where spilling of excess concrete during de-moulding is avoided. This is obtained by the characterising part of claim 1. The method may optionally be embodied as defined by the features of dependent claims 2-6. When the spigot end is cast with a firm profile ring, the inner mould part continues to move upwardly with respect to the outer mould part, whereby the distributor wheel is pushed up through the opening of the profile ring. During the continued rise the inner mould part, too, will be pushed up through the opening of the profile ring, and it is important that the mould part fills the opening as well as possible considering the vibration amplitude, such that it can cut off the spigot end of the pipe from the excessive amount of concrete in a well-defined manner. This cut-off is promoted by forming the transition between the conical portion and the cylindrical portion of the inner mould part as a sharp edge. To collect the excess amount of concrete formed in the cutting-off of the spigot end, according to the invention, the profile ring has an upwardly hopper-shaped expansion which also serves as a filling hopper. The concrete residue collected in this hopper is vibration-compressed, and it will therefore have such a stable state that it will hang as a ring downwardly in the hopper when the inner mould part is pulled down through the opening of the profile ring during the demoulding operation. However, the concrete residue will be loosened by the vibrations and/or the dropping fresh concrete in the next working cycle, so that the concrete residue will be incorporated as a component in the next pipe. It has been found that the best results are obtained when the casting process is terminated in that the distributor wheel rises up through the opening with a gradually decreasing speed of rotation and/or gradual vibration intensity. The invention is explained more fully by the following description, which just serves as an example, with reference to the drawing, in which fig. 1 is a perspective view of a distributor wheel mounted on the top of an inner mould part, and figs. 2-6 are sectional views at various stages in the casting of a concrete pipe by means of the distributor wheel shown in fig. 1. Fig. 1 shows a distributor wheel 1 which is rotatably mounted on an inner mould part 2 by means of a hub 3, from which four blades 4 radiate, said blades being upwardly connected with a stiffening ring 5 to stabilise the structure. The inner mould part 2 upwardly terminates in an upwardly converging cone 6, and a journal 7 extends upwardly from the centre of the cone to mount the wheel. The journal 7 is journalled in a bearing (not shown), which is positioned inside the inner mould part 2, and can be caused to rotate by means of a power transmission device (not shown) . A vibrator (not shown) for vibrating the concrete is moreover provided inside the top of the inner mould part.. The blades themselves, which may e.g. be made of sheet iron with a suitable thickness, are moreover separately shaped as a helicoid directed rearwardly with respect to the direction of rotation. It now appears from figs. 2-6 how the distributor wheel shown in fig. 1 is used for casting of a concrete pipe 8 with a socket 9, a shank 10 and a spigot end 11. In addition to the inner mould part 2 with the distributor wheel 1, the overall mould system also comprises an outer mould part 12, which stands on a bottom ring 13, which simultaneously serves as a pallet for the cast pipe 8. The bottom ring 13 in turn rests on a table 15, associated with the casting machine, via vibration damping rubber buffers 14. A profile ring 16 is secured upwardly in the outer mould part 12 to shape the spigot end 11 of the pipe. Upwardly the profile ring 16 merges into a hopper-shaped expansion 17, which serves as a filling hopper for the concrete fed by means of a belt conveyor 18 in the shown case. As will appear, the outer mould part 12 is stationary during the casting process, while the inner mould part 2 moves from below up into the outer mould part, and, simultaneously, the distributor wheel 1 rotates in the direction indicated by the arrow, and the vibrator (not shown) emits the vibrations indicated by the symbol 19. The fresh concrete drops from the belt conveyor 18 via the filling hopper 17 down through the upwardly open spaces between the rearwardly directed screw-shaped blades 4 of the distributor wheel, which then press the concrete downwardly and outwardly in a manner such that the concrete is distributed evenly and uniformly in the ring gap between the two mould parts 2, 12, the downwardly directed portion of the movement of the concrete being facilitated because of the downwardly inclined face on the cone 6 of the inner mould part 2. In fig. 2 the casting of the socket 9 of the pipe has just been completed, and casting of the shank 10 of the pipe has been initiated. During the continued casting concrete is successively filled from the belt conveyor 18, while the inner mould part 2 continues its upward movement in the outer mould part 12. Fig. 3 shows a later stage in the casting of the shank 10 of the pipe, and in fig. 4 the shank has been finished, while casting of the spigot end 11 is in its final phase where the distributor wheel 1 is on its way up through the opening of the profile ring 16. Even though the distributor wheel, as shown, fills this opening almost completely, it has constantly been possible for fresh concrete to pass through the wheel during casting of the spigot end for replenishing the area of difficult access below the profile ring. For the distributor wheel 1 to pass up through the opening of the profile ring 16, it must have an outside diameter which is slightly smaller than this opening. The same applies to the inner mould part 2, which subsequently moves up through the opening (fig. 5), and which, with a sharp edge 20, cuts off the finished spigot end 11 from the excess concrete material 21. However, the clearance between the inner mould part and the opening of the profile ring must be as small as possible and preferably just slightly greater than the greatest vibration amplitude to ensure that the spigot end will be cut off sharply and thereby be terminated with a precise shape. The excess concrete material 21, which has now been cut off from the finished pipe, is collected downwardly in the filling hopper 17, where the excess concrete 21 is vibration compressed. The excess concrete 21 will therefore have a sufficiently great stability of shape to remain in the filling hopper 17 when the inner mould part 2 is pulled out of the finished pipe, as shown in fig. 6. The concrete ring 21 will be loosened later in the next working cycle by the vibrations during the next working cycle, and, as shown in fig. 2, drop down and mix with the fresh concrete from the belt conveyor 18. De-moulding of the cast pipe is completed in the shown case by pulling the outer mould part 12 upwardly in a conventional manner until it is free of the pipe 8, which is now ready for being driven out to a curing site, standing on the bottom ring 13. Less concrete is consumed for casting the spigot end per unit of length than for casting the shank. Accordingly, the speed of rotation of the distributor wheel and/or the vibration intensity is gradually reduced during the passage of the distributor wheel through the opening of the profile ring. This also ensures a very gentle termination of the vibration compression process, which finally just takes place with the lowermost tip of the blades at the sharp edge 20 of the inner mould part as far as the spigot end is concerned. Although the method according to the invention embodies production of cylindrical pipes as have been described above and shown in the drawing, other embodiments are readily conceivable within the scope of the invention, and such other embodiments may e.g. be adapted to cast pipes which are four-sided or six-sided exteriorly. Correspondingly, for the casting there may conceivably be used other materials, which are suitable for casting by means of vibration compression, than concrete e.g. the material described in the Danish Patent Application 1175/89 "A method of making acid-proof sulphur concrete pipes".

Claims: A method for vertical casting of pipes (8) of concrete or a similar material on a machine, said machine comprising inner and outer mould parts (2, 12), respectively, means for axially displacing the inner and outer mould parts with respect to each other during the casting process, a profile ring (16) secured to the outer mould part or an axially upwardly and downwardly displaceable part of the machine, said profile ring upwardly continuing in a hopper shaped expansion (17), an axially journalled distributor wheel (1) being rotatably mounted on the top of the inner mould part, where the method comprises steps of: a) gradually moving the inner mould part in an upwardly direction while filling material through the profile ring and compressing material between the inner and outer mould parts, and b) continuing movement of the inner mould part to a position where the distributor wheel is placed above the profile ring, and c) depositing excess material (21) in the expansion (17), characterised in that at least one vibrator (19) is preferably arranged upwardly in the inner mould part, and that the method comprises a further step of: d) continuing movement of the inner mould part to a position where the distributor wheel is placed above the excess material and vibration compressing the excess material (21) in the expansion (17) caused by the vibrator in the inner mould part. A method according to claim 1, where the method comprises further steps of: e) de-activating the at least one vibrator, and f) moving the inner mould part downwardly to a position below the pipe (8). A method according to claim 1 or 2, where the method comprises that the excess concrete (21) is loosened during a following working cycle and used in casting of a pipe (8). A method according to one or more of claims 1-3, where distributor wheel is having a plurality of blades (4), and where the method comprises that the blades are used for distributing the material in the space between the two mould parts (2,12). A method according to one or more of claims 1-4, where the top of the inner mould part is shaped as an upwardly converging cone (6) and a transition between the cone and a cylindrical portion of the inner mould part (2) is formed by a sharp edge (20), and where the method comprises the step of cutting of excess concrete (21) from the pipe by passing the sharp edge through the profle ring (16) to terminate the end of the pipe with a precise shape. A method according to one or more of claims 1-5, where the method comprises that the speed of rotation of the distributor wheel is gradually decreased during passage of the profile ring.

Inventors: HERRMANN BENT, HERRMANN, BENT
Applicants: PEDERSHAAB CONCRETE TECHNOLOGI, PEDERSHAAB CONCRETE TECHNOLOGIES A/S
Application year: 1992
Main classification: B28B21
IPC codes: B28B21