EP0406612B1

EP0406612B1 - Process and equipment for realizing reinforced concrete pipes

Info

Publication number: EP0406612B1
Application number: EP90111506A
Authority: EP
Inventors: Croci Piero
Original assignee: Croci Mario & Figli Srl
Current assignee: Croci Mario & Figli Srl
Priority date: 1989-07-03
Filing date: 1990-06-19
Publication date: 1993-10-20
Anticipated expiration: 2010-06-19
Also published as: IT1230976B; IT8921074A0; DE69004015D1; EP0406612A1; ES2047761T3; DE69004015T2

Description

The object of the present invention is a process and relative equipment for realizing pipes in concrete reinforced with preassembled cages, used particularly in sewage mains.
Pipes of this type are at present realized with different systems, all of which have different kinds of drawbacks.
A first system consists in setting a horizontally positioned mold in fast rotation, inside of which the pipe is formed by centrifugation. This system allows concrete pipes to be realized with or without reinforcement; it is, however, very expensive and also has the drawback of segregation of the components of the mixture.
Another system consists in realizing the pipe vertically, by means of a rotating mandrel provided with fins, shaped like the portions of a propeller. These fins compress the ccncrete introduced into the mold, generating an upward thrust of the mandrel until the pipe is completely formed. With this system it is not possible to insert a reinforcement in the pipe, since the fins of the mandrel would interfere with it.
A variation of this process is the "Packerhead" system, which uses a rotating mandrel provided with rollers tangential to the internal diameter of the pipe, which cast and distribute the ccncrete beyond the reinforcement and then compress it, thanks to their high rotation speed. The disadvantages of this method are the high power required, severe wear on the mandrel components and the torsion to which the reinforcement is subjected. This torsion occurs in spite of the use of several series of overlapping, counter-rotating rollers and of hydraulic cylinders positioned on several horizontal planes, intended to enter the reinforcement and counteract its rotation.
Another system of manufacture, to which the present invention relates, is that using pressure-vibration. This consists of locating a vibrating nucleus inside a mold, which is gradually filled with concrete which is compacted by the vibrating nucleus.
With this system an excellent article is obtained in concrete which is not reinforced, or which has a semi-rigid reinforcement, made up, for example, of circumferential rods joined together by chains. But when it is necessary to realize a reinforced pipe with a reinforcement consisting of a rigid cage, the latter is drawn into rotation by the tangential component generated by the rotary motion of the vibrator positioned inside the nucleus. This rotation of the reinforcement causes cracking in the concrete, which occurs after the pipe is dismantled, because of the spring back of the reinforcement itself.
In order to limit this effect, an attempt is made to keep the reinforcement centred and prevent its rotation during the formation of the pipe, by means of hydraulic cylinders positioned on several horizontal planes. These systems are not satisfactory because they cannot prevent the bending of the longitudinal rods of the reinforcement between the planes on which the cylinders are positioned.
DE-C-882 667 and FR-A-1 246 252 describe devices for manufacturing pressure-vibrated concrete pipes, which are not reinforced and in which the whole head of the nucleus, positioned axially inside a mold, is vibrated.
With said devices it is impossible either to realize reinforced concrete pipes or to place rotating blades on the vibrating head of the nucleus, in order to obtain a uniform distribution of the concrete in the annular space which is formed between the mold and the nucleus.
SOVIET INVENTIONS ILLUSTRATED, week B38, 31st October 1979, abstract No. J1123B/38, Derwent Publications, Ltd. London, GB; & SU-A-638 473 (UKR. DNEPR. CONS. PROD.) 28.12.1978 describe a device for making pressure-vibrated pipes comprising a vibrating part which is positioned between two non-vibrating parts, according to the preamble of claim 4. Such a device has, however, the tipical inconveniences of the pressure-vibrated devices previously shown, i.e. the production of tangential forces which would provoke torsions on possible reinforcements placed inside the mold.
Therefore the aim of the present invention is to realize a process and relevant equipment for manufacturing in particular pressure-vibrated reinforced concrete pipes which will prevent the generation of tangential forces, which cause the rotation of the concrete and, consequently, the deformation of the reinforcements.
With the process according to the invention, it will be possible therefore to make use of rigid reinforcements consisting of preassembled metallic cages, composed of longitudinal rods and circumferential rods joined together by welding or binding.
This aim is achieved with the process according to the invention, which foresees a relative feed motion of a nucleus in an external mold, into which the concrete is gradually fed and distributed, being compacted gradually, as it is fed, by means of a vibrating part of the head of the nucleus. This vibrating part has a first truncated-conical length provided with radial separators, suitable for preventing the rotation of the vibrated concrete and therefore of the reinforcement, if any, which is inserted into the mold, and a perfectly cylindrical band which gauges and smooths off the internal wall of the pipe during formation. The remainder of the nucleus is not vibrated, including the frontal part of the head, consisting of a conical body on which rotating blades are located which distribute the concrete in the annular chamber which is formed between the vibrating part of the head of the nucleus and the mold.
Further characteristics of the process and equipment according to the invention will be explained more clearly in the detailed description which follows, referring to one of its purely exemplary, and therefore not restrictive, embodiments, shown in the enclosed drawings, in which:

Figure 1: is a diagrammatic elevation of the equipment according to the invention, with the mold in section, during the formation of a reinforced pipe;
Figure 2: is an enlargement of the head of the nucleus in Figure 1.

With reference to these figures, 1 indicates a cylindrical body or nucleus, positioned vertically on axis with an external mold 2, into which it can be inserted. The mold 2 is located on a base ring 3, on which a rigid metallic reinforcement 4 also rests, housed inside the mold. The reinforcement 4 comprises circumferential rods 5, connected to each other by longitudinal rods 6.
A vibrating part 7 is foreseen on the head of the nucleus 1, insulated resiliently from it by means of dampening devices 8, shown with shading in figure 2. The vibrating part 7, which is set in vibration by known means positioned inside it, has a first truncated-conical length 9, on which radial separators 10 are positioned, joined together by a cylindrical band 11, whose diameter is substantially equal to that of the body of the nucleus 1. The end part or top of the head of the nucleus consists of a conical body 12, which does not vibrate either, on which the blades 13 rotate.
The process according to the invention is carried out in the following manner.
Concrete 14 is fed, for example by being dropped from a conveyor belt 15, into the mold 2, prearranged as in figure 1. The concrete drops onto the head of the nucleus 1 and is distributed by the rotating blades 13, with the aid of the conveyor cone 12, in the annular space which is formed between the mold 2 and the vibrating part 7 of the head, burying the reinforcement 4. During the phase when the pipe, shown with reference number 16 in figure 1, is being formed, relative feed motion is foreseen of the nucleus 1 in the mold 2. This relative feed motion can be obtained by providing the nucleus 1 with a rising motion, or by providing the mold 2 with a downward motion, or by moving the nucleus 1 and the mold 2 jointly.
During the feed motion of the nucleus 1 in the mold 2, the concrete 14 is gradually compacted by the vibrating part 7 of the head. While it is being compacted, the separators 10, foreseen on the truncated-conical length 9 of the vibrating part, prevent the rotation of the vibrated concrete, and therefore the torsion of the reinforcement 4, which is kept perfectly in a rectilinear vertical position.
The cylindrical band 11 which follows the truncated-conical length 9 of the vibrating part 7 gauges and smoothes the internal wall of the pipe 16 being formed.
The compacting of the wall of the pipe 16 is therefore due to the truncated-conical length 9 of the vibrating part 7, through the action of centrifugal force generated by the vibrator positioned in it.
The specific shape of the vibrating part 7 and the feed motion of the nucleus 1 in the mold 2, generate forces whose components - both radial and vertical (the latter directed upwards) - act on the cement mixture, which surrounds the reinforcement 4 without leaving empty spaces.
Since the body of the nucleus 1 does not vibrate, it does not cause rotation of the cement mixture and consequently of the reinforcement 4, and its only task is to support the wall of the pipe 16 as it continues to be formed.
The finish of the upper part of the pipe 16 is obtained as usual, by means of a smoothing ring (not shown), provided with rotary motion and vertical pressure, from top to bottom.
The finished pipe is then slid out of the mold 2 and transported to the drying area.

Claims

A process for realizing pressure-vibrated concrete pipes (16), in which the concrete (14) is fed into a vertical mold (2) surrounding a nucleus (1), and is compacted by means of a vibrating part (7) of the head of the nucleus (1) has smaller dimensions than the body of the nucleus and which is positioned between non-vibrating parts consisting, respectively, of the body of the nucleus (1) and of the end part or top (12) of the head of the nucleus, characterized in that a relative feed motion of the nucleus (1) in the mold (2) is foreseen, and that said vibrating part (7) of the nucleus (1) has a first truncated-conical length (9), provided with radial separators (10), suitable for preventing the rotation of the concrete during compacting of the same, followed by a cylindrical band (11), suitable for gauging and smoothing the internal wall of the pipe (16) being formed.
A process according to claim 1, characterized in that it foresees the positioning of a rigid reinforcement (4) inside the mold (2), in such a way as to obtain a reinforced pipe (16).
A process according to claim 1 or 2, characterized in that said non-vibrating end part or top (12) of the head of the nucleus (1) is formed by a conical length, on which rotating blades (13) are located, suitable for distributing the concrete (14) in a uniform manner in the annular space which is formed between the mold (2) and the vibrating part (7) of the nucleus (1).
Equipment for making pressure-vibrated concrete pipes (16) comprising a vertical nucleus (1), positioned axially to an external mold (2), into which the concrete (14) is fed, for example by being dropped, said nucleus (1) having a vibrating part (7) in correspondence with its head, positioned between two non-vibrating parts, consisting, respectively, in the body of the nucleus (1) and in the end part or top (12) of the head of the nucleus, characterized in that said nucleus (1) is provided with a relative feed motion with respect to the mold (2), and said vibrating part (7) comprises a first truncated-conical length (9) with radial separators (10), followed by a cylindrical band (11) with a diameter substantially equal to that of the body of the nucleus (1).
Equipment according to claim 4, characterized in that said vibrating part (7) is resiliently insulated from the body of the nucleus (1) by means of dampening devices (8), and is likewise resiliently insulated from the end part or top (12) of the head of the nucleus.
Equipment according to any one of the claims 4 or 5, characterized in that said non-vibrating end part or top (12) of the head of the nucleus is formed by a conical body, on which rotating blades (13) are positioned.
Equipment according to any one of the claims from 4 to 6, characterized in that between said nucleus (1) and said mold (2) a rigid reinforcement (4) is positioned.