Forming device for precast concrete ceiling slabs, method for their manufacture and precast concrete ceiling slab

Abstract

Method for producing a precast concrete slab with voids extending longitudinally through the concrete material, comprising the following process steps: - Providing a molding device (2) with core tubes (9) and reinforcement in a mold cavity (7), - Pouring concrete material (17) into the mold cavity (7), - controlled application of vibrations to the form table (4) and the core tubes (9) for compaction of the concrete material (17) such that a compaction gradient transverse to the direction of extension of the cavities formed by the core tubes (9) in the precast concrete slab is generated by selectively controlling drive motors (14) for the vibrations of the core tubes (9), wherein, in order to achieve areas of higher concrete density, the core tubes (9) located there are subjected to a higher vibration intensity or duration, - Smoothing the top surface (19) of the concrete material (17), - Extraction of the core tubes (9) after sufficient stiffening of the concrete material (17), and - Removal of the formed precast concrete ceiling slab.

Description

[0001] The invention relates to a method for producing a precast concrete ceiling slab according to claim 1, a precast concrete ceiling slab having the features specified in the preamble of claim 2 and a molding device having the features specified in claim 6.

[0002] Regarding the background of the invention, it should be noted that various disadvantages of the prior art exist in the field of precast concrete ceiling slabs. A fundamental problem is the sufficient compaction of the material poured into the molding device for the ceiling slab. This molding device typically has a molding table with side walls, which forms a plate-shaped mold cavity open at the top. A vibration device is provided for the molding table - usually underneath it. Furthermore, extendable core tubes are arranged in the mold cavity, which form continuous, tubular cavities in the precast concrete ceiling slab in the span direction. Such ceiling slabs are manufactured, for example, by the applicant under the German trademark "DENNERT-DX-DECKE" and have been marketed on a large scale for years.

[0003] The problems mentioned above include, for example, the degree of compaction of the poured concrete material, which is limited when using a vibrating forming table. High compaction levels require long vibration times and high vibration intensities, which increases the process and equipment costs for slab production.

[0004] A particular problem arises in the production of prestressed precast concrete slabs. These are traditionally manufactured using a type of continuous production process, in which a mold carriage with two opposing lateral mold walls moves along a production line, producing a concrete strip up to 100 m long. Tensile reinforcement runs in this concrete strip in the direction of production. Transverse reinforcement is generally not possible due to the production plant, so the width of such prestressed concrete slabs is limited to approximately 1 m.

[0005] Another, as yet unsolved problem with prestressed concrete ceiling slabs is the fact that with different spans of adjacent prestressed concrete slabs, different degrees of deflection result due to their different weights, so that the adjacent slabs can have an undesirable height offset at the joint.

[0006] In the published prior art, DE 44 24 526 A1 discloses a precast floor slab with continuous cavities and a molding device therefor, in which these cavities are formed by vibrating tubes inserted into the molding box. Measures for selectively controlling these vibrating tubes are not disclosed in the document.

[0007] GB 2 222 981 A discloses a forming device for lightweight concrete slabs in which a reduction in the specific gravity of the slab is achieved by embedding plastic particles in the concrete material. The concrete material is introduced and compacted in layers at two different vibration levels.

[0008] EP 0 253 043 A2 shows a flow production of prestressed hollow core slabs, using a vibration device to compact the concrete material.

[0009] From DE 33 42 950 A1 a method for producing bricks from clay is known, in which the clay mass is extruded by adding vibration energy before passing through the mold mouthpiece.

[0010] Finally, DE 199 07 781 A1 discloses the use of external vibration devices - so-called vibration bottles - for compacting concrete material that was poured into a mold box open at the top to produce a concrete ceiling slab.

[0011] Based on the problems described above, the invention is based on the object of improving a manufacturing method, a precast concrete ceiling slab produced thereby and a forming device for precast concrete ceiling slabs in such a way that a rapid and variable compaction of the concrete material during production is possible and, based on this, the manufacturing method and the precast concrete slabs produced thereby can also be designed variably.

[0012] This object is achieved from a manufacturing point of view by the method steps specified in claim 1 as follows: - Providing the molding device with core tubes and reinforcement in the mold cavity, - Pouring concrete material into the mold cavity, - controlled application of vibrations to the forming table and the core tubes to compact the concrete material in such a way that, by selectively controlling drive motors for the vibrations of the core tubes, a compaction gradient is generated transversely to the direction of extension of the cavities formed by the core tubes in the precast concrete floor slab, whereby, in order to achieve areas of higher concrete density, the core tubes (9) located there are subjected to higher vibration intensity or time, - Smoothing the top of the concrete material, - Pulling out the core tubes after the concrete material has sufficiently stiffened, and - Removing the finished concrete ceiling slab.

[0013] A vibration unit is also provided for the core tubes. This means that the concrete material in the mold cavity is compacted not only by the mold table itself, but also by the vibrating core tubes.

[0014] This fundamental measure creates the basis for producing precast concrete slabs in a particularly variable and efficient manner, so that according to the characterizing part of claim 2, they have a degree of compaction in their concrete material that is variable across the slab so that a compaction gradient runs transversely to the direction of extension of the cavities in the concrete slab.

[0015] Furthermore, according to the characterizing part of claim 6, the core tubes are each equipped with a separately controllable internal vibrating unit, i.e., a vibration unit. This allows different core tubes in one and the same slab to be vibrated for different lengths of time and intensity, so that the degree of compaction of the concrete material can be variably adjusted across the slab, transverse to the core tubes.

[0016] Due to the planned individual extraction of the core tubes from the mold cavity, it is possible to produce any statically necessary solid strips without continuous cavities in the ceiling panel element.

[0017] According to a further preferred embodiment of the molding device, a tensile reinforcement can be clamped between the opposite side walls parallel to the core tubes for the production of prestressed concrete slabs. Since transverse reinforcement can be simultaneously inserted in the mold cavity, prestressed concrete slabs with a long span and a significantly greater width than the prior art elements—namely, up to 2.50 m instead of approximately 1 m—can be produced.

[0018] In summary, the core feature of the invention is the vibration control of the forming table and the core tubes. This allows for optimal, rapid and high compaction of the concrete material to be achieved, for example, by simultaneously maximizing the vibration of the forming table and all core tubes. By selectively vibrating individual core tubes to a lower degree, lower compaction can be achieved in this area of ​​the slab.

[0019] The achievable flexibility in the compaction of the concrete material makes it possible, in a simple manufacturing process, to compact concrete slabs with a long span, for example, to a lower degree, while those with a short span are more densely compacted. The latter therefore have a comparatively higher weight and thus a higher deflection than a concrete slab with the same span, whose concrete material is compacted to a lower degree. This allows for deflection differences between adjacent concrete slabs of different spans to be compensated, keeping their undersides at the same level. This prevents a height offset at the joint between such adjacent slabs.

[0020] Further features, details and advantages of the invention will become apparent from the following description, in which an embodiment is explained in more detail with reference to the accompanying drawings. Fig.1 shows a perspective view of a forming device in an intermediate manufacturing step of a prestressed concrete floor slab.

[0021] In the attached drawing, a forming device 2 is mounted on a roller conveyor 1 and is movable via rollers 3 in the production direction P. The situation shown shows the concreting station.

[0022] The molding device 2 has a flat mold table 4, which, together with the longitudinal and transverse side walls 5, 6 surrounding it, forms the top-open, plate-shaped mold cavity 7. Bearing recesses 8 are provided in the opposite longitudinal side walls 5 at a grid spacing R, through which core tubes 9 can be alternately inserted into the mold cavity 7 from the two opposite sides of the molding device 2 and withdrawn therefrom. This movement is indicated by the double arrows D in the drawing. The core tubes 9 form continuous, tubular cavities in the span direction in the finished concrete slab, as has long been known.

[0023] The drawing also shows a tensile reinforcement 10 in the form of tension rods clamped between the two opposite longitudinal side walls 5, each of which is arranged below the core tubes 9, approximately in their interstices. The clamping heads 11 of the rods of the tensile reinforcement 10 are located on the outside of the longitudinal side walls 5.

[0024] Furthermore, a transverse reinforcement 12 is provided, running transversely to the core tubes 9, which is formed by reinforcing steels inserted into the mold cavity 7 without tensile stress. The transverse reinforcement 12 is thus designed as slack reinforcement.

[0025] The core tubes 9 are provided with a cover plate 13 at their ends not inserted through the mold cavity 7, to which a feed drive (not shown in detail) is attached, responsible for the insertion and withdrawal movement (double arrows D) of the core tubes 9. Furthermore, a drive motor 14 is located on each cover plate 13, which sets in motion an internal vibrating shaft (not shown) in the core tubes 9 by means of a control system (not shown in detail). The mold table 4 itself can also be set into vibration by an underfloor vibrator 15, indicated by dashed lines in the drawing.

[0026] Finally, the molding device shown has a concrete feed 16 in the form of a concrete chute running across the width of the mold cavity 7.

[0027] To produce a precast concrete ceiling slab, the forming device 2 is pre-equipped with the tensile reinforcement 10 between the side walls 5 and the transverse reinforcement 12 at a location not shown and then moved into the concreting station shown in the drawing. There, the core tubes 9 are inserted alternately from opposite sides into the bearing recesses 8 so that they extend across the entire width of the mold cavity 7, which corresponds to the span direction of the ceiling slab to be produced. Concrete material 17 is then successively poured from above using the concrete feeder 16 until the mold cavity 7 is completely filled—if necessary, with an excess.

[0028] The concrete material 17 is compacted by means of the subfloor vibrator 15 and the vibration of the core tubes 9 by means of the drive motors 14. By selectively controlling the drive motors 14 and correspondingly stronger, weaker, or no vibration of the core tubes 9, a compaction gradient can be induced transversely to the direction of extension of the cavities formed by the core tubes 9 in the concrete slab corresponding to the mold cavity 7. A high degree of compaction of the concrete material can be achieved by particularly intensive vibration of the subfloor vibrator 15 and the core tubes 9, while a lower degree of compaction can be achieved by omitting vibration of the core tubes 9.

[0029] After compacting the concrete material 17, possibly adding more concrete material 17, the exposed upper surface 19 of the thus formed precast concrete ceiling slab is leveled by a smoothing device. After a sufficient setting time, the core tubes 9 are then withdrawn from the forming device 2, which is then moved to another production position for demoulding the slab.

[0030] In summary, the selective activation of subfloor and core tube vibration allows for virtually any combination of compaction energy to be applied. Furthermore, the forming device shown can also produce a strip-shaped solid area 18 by omitting the vibration of core tubes 9 during production. In this solid area, there are no cavities located in the slab at the given grid spacing R.

Claims

[1] Method for producing a prefabricated concrete floor slab with cavities running longitudinally through the concrete material, comprising the following process steps: - Providing a molding device (2) with core tubes (9) and a reinforcement in a mold cavity (7), - filling concrete material (17) into the mould cavity (7), - controlled application of vibrations to the forming table (4) and the core tubes (9) to compact the concrete material (17) in such a way that, by selectively controlling drive motors (14) for the vibrations of the core tubes (9), a compaction gradient is generated transversely to the direction of extension of the cavities formed by the core tubes (9) in the precast concrete floor slab, wherein, in order to achieve areas of higher concrete density, the core tubes (9) located there are subjected to higher vibration intensity or time, - smoothing the top surface (19) of the concrete material (17), - pulling out the core tubes (9) after the concrete material (17) has sufficiently stiffened, and - Removing the finished concrete ceiling slab. [2] Prefabricated concrete ceiling slab with cavities running longitudinally through the concrete material (17), produced by a method according to claim 1, characterized by that the concrete material (17) has a degree of compaction which varies over the precast concrete ceiling slab in such a way that a compaction gradient runs transversely to the direction of extension of the cavities (7). [3] Precast concrete ceiling slab according to claim 2, characterized by that at least one solid area (18) is provided without cavities arranged according to the given grid spacing (R) in the prefabricated concrete ceiling slab. [4] Precast concrete ceiling slab according to claim 2 or 3, characterized by that a tension reinforcement (10) is provided in particular parallel to the cavities of the prefabricated concrete ceiling slab. [5] Precast concrete ceiling slab according to claim 4, characterized by that a slack reinforcement (12) is provided transversely to the tension reinforcement (10). [6] Forming device for prefabricated concrete ceiling slabs with cavities extending longitudinally through the concrete material for carrying out the method according to claim 1, comprising - a mold table (4) forming the plate-shaped mold cavity (7) with side walls (5, 6), - a vibration device for the forming table (4), - core tubes (9) which are arranged in the mould cavity (7) in an extendable manner, - vibration units for the core tubes (9), wherein the core tubes (9) are each equipped with a separately controlled internal vibration unit driven by drive motors (14) as a vibration unit, and - a control system which is set up and designed in such a way that, by selectively controlling drive motors (14) for the vibrations of the core tubes (9), a compaction gradient is generated transversely to the direction of extension of the cavities formed by the core tubes (9) in the precast concrete ceiling slab, wherein, in order to achieve areas of higher concrete density, the core tubes (9) located there are subjected to higher vibration intensity or time. [7] Molding device according to claim 6, characterized by that the core tubes (9) are mounted so that they can be individually pulled out of the mold cavity (7) via the side walls (5). [8] Molding device according to one of claims 6 or 7, characterized by that the drive motors (14) for the vibration units of the core tubes (9) are mounted on an end of the core tubes (9) remaining outside the mold cavity (7). [9] Molding device according to one of the preceding claims 6 to 8, characterized bythat a tension reinforcement (10) can be clamped parallel to the core tubes (9) between the opposite side walls (5) for the production of prestressed concrete slabs. [10] Molding device according to one of the preceding claims 6 to 9, characterized by that a transverse reinforcement (12) running transversely to the core tubes (9) can be inserted into the mold cavity (7).

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