Formwork core, formwork device with same and method for producing a hollow body

Abstract

In a formwork core (1) for producing a hollow body (2) from a casting compound (B), wherein the hollow body has at least one extraction opening (20) comprising an inner formwork wall designated as an inner formwork (10), and a support structure (15) supporting the inner formwork, wherein the inner formwork is designed to be contractible such that the formwork core has a smaller cross-section in an extraction configuration than in a formwork configuration, it is proposed that the inner formwork essentially comprises a thermoplastic material and is configured such that a temperature reduction acting in the inner formwork causes the contraction (140) of the inner formwork, such that the formwork core can be removed from the hollow body non-destructively through the extraction opening (20) in the extraction configuration.Furthermore, a formwork device with a formwork core and a method (100) for producing a hollow body from a casting compound are presented.

Description

[0001] The invention relates to a formwork core for producing a hollow body from a casting compound according to the preamble of claim 1.

[0002] The invention is preferably applicable in connection with concrete materials, so the following discussion focuses in particular on the example of concrete material processing. However, the invention is not limited to concrete, but is equally applicable to other curable casting compounds.

[0003] A casting compound is defined here as an initially flowable, formless material which, through hardening, acquires a final, geometric shape, for example, concrete materials, plastics, or the like. Hardening in the context of the present invention encompasses the phase transition from a flowable casting compound to a solid molded body and is used synonymously with terms such as solidification, hardening, setting, reaction, or similar processes.

[0004] In this context, a hollow body refers to a three-dimensional molded body, which, according to the prior art, is produced by casting around a formwork core. The formwork core has an inner formwork wall, referred to as the inner formwork, and a support structure that supports the inner formwork, and is, in particular, part of a formwork system. Together with an outer formwork, the inner formwork defines a casting chamber, which essentially corresponds to the geometry of the hollow body. Examples of hollow bodies known from practice, especially large-format (concrete) hollow bodies, are space-defining, (quasi-)monolithic building elements such as modular units, garages, or the like. To allow for the removal of a formwork core from the hollow body, these hollow bodies have a number of extraction openings.

[0005] In the context of the presented invention, "number" means a singular or plural feature.

[0006] Formwork cores, similar to lost inner formwork, are a common practice. This means that once the casting compound, particularly the concrete material, has hardened, the inner formwork is destroyed, allowing it to be removed from the hollow body. However, in mass production and the manufacture of large-format components, formwork cores that can be removed without destruction are preferable. It is not always possible to incorporate demolding slopes or similar features, as rectangular masonry and geodesically level floors are often desired.

[0007] Also known are formwork cores that are designed to be movable. In this design, the formwork core can be contracted from a formwork configuration with a first formwork core cross-section into a removal configuration with a second, smaller formwork core cross-section. The formwork configuration comprises the components or component dimensions of the formwork core before and / or during a formwork process for producing a hollow body. As soon as the components of the formwork core have assumed dimensions that allow the removal of the formwork core, in particular non-destructive removal of the formwork core, from the hollow body, the removal configuration is reached. The contraction or shrinkage of the formwork core thus enables it to be removed from the hollow body non-destructively through a removal opening.

[0008] DE 14 34 748 A1 describes a formwork device for the production of large-format hollow concrete bodies with formwork elements adjustable against each other, which are movable by means of hydraulically or pneumatically actuated actuators to contract the formwork core, forming a reduced formwork core cross-section.

[0009] DE 295 19 298 U1 describes a formwork device for the production of small-format components, namely concrete rings for chimneys. The formwork core is contracted to adjust the removal configuration by reducing the distance between opposing formwork elements, and thus the cross-section of the formwork core, using spindles.

[0010] Problematic aspects of the current state of the art include the connection points between the movable formwork elements. These can lead to undesirable, offset surfaces on the finished concrete element, joints within the concrete element, and / or ribs on the concrete element. Furthermore, the known contraction is usually only successful in a specific circumferential direction of the core. Especially when, in addition to side formwork elements, bottom and / or slab formwork elements are also used for the formwork core, the mechanics between the individual formwork elements become complex, and the transitions between them become problematic. Moreover, the mechanics and the transition areas can be affected by casting material residues, particularly from a concrete compound, which complicates the smooth operation and increases wear of the mechanics. This, not least due to increased maintenance requirements, leads to high production costs.

[0011] Therefore, the purpose of the presented invention is to provide a solution for the precise, cost-effective and simple production of a hollow body.

[0012] The problem is solved by a formwork core according to the features of claim 1 and by a manufacturing method according to the features of claim 12. Features of the invention are discussed below. Further advantageous aspects, details, and embodiments of the invention will become apparent from the dependent and deferred claims and from the description.

[0013] According to a first aspect, the invention relates to a formwork core for producing a hollow body from a casting compound, wherein the hollow body has at least one extraction opening, comprising an inner formwork wall referred to as the inner formwork, and a support structure supporting the inner formwork, wherein the inner formwork is designed to be contractible, such that the formwork core has a smaller cross-section in an extraction configuration than in a formwork configuration, wherein the inner formwork essentially comprises a thermoplastic material and is configured such that a temperature reduction effective in the inner formwork causes the inner formwork to contract, such that the formwork core can be removed from the hollow body non-destructively through the extraction opening in the extraction configuration.

[0014] In other words, the invention is based on the idea of ​​using thermally induced deformation of a plastic inner formwork to selectively contract the inner formwork, particularly for shortening formwork walls and thus reducing the spacing between formwork elements. The deformation creates a (demolition) gap between the inner formwork and a substantially cured hollow body, thereby separating the inner formwork from the hollow body surface. In the removal configuration, the gap can advantageously be 1 to 30 mm, preferably 10 to 20 mm, and particularly preferably 15 mm. The proposed solution is particularly advantageous because it can be easily implemented in practice without requiring extensive acquisitions. This is because the ambient conditions common in practice with regard to air temperature and humidity do not need to be significantly altered.

[0015] Surprisingly, a formwork panel, which essentially comprises a thermoplastic material, or in particular consists of a thermoplastic material, proves to be especially suitable for providing sufficient contraction to allow non-destructive removal of the formwork core from the hollow body, i.e., without destroying or damaging the hollow body or the inner formwork itself. Initial non-public prototypes have shown that the required temperature reduction is comparatively small. A preferred reduction of the process temperature acting on the inner formwork can be, for example, between 5 and 50 K, particularly between 10 and 40 K, and most preferably between 15 and 30 K.

[0016] Advantageously, the inner formwork can comprise one or more of the following groups of plastics: polyethylene (PE), polyvinyl ether (PVE), polyvinyl butyral (PVB), polyvinyl acetate (PVA), thermoplastic polyurethane (TPU), and acrylate polymers. With a coefficient of linear expansion of 200 × 10⁻⁶ K / K at 20 °C and a temperature difference of approximately 50 K, PE, for example, contracts by about 1%. The resulting dimensional changes are sufficient to detach the inner formwork from the at least partially cured casting compound. PVE, in particular, is mechanically highly resilient, wear-resistant, and characterized by excellent chemical resistance. Furthermore, it has been demonstrated that, for example, no significant adhesion develops with concrete, resulting in a higher-quality surface finish after the formwork core is removed from the cavity.Good coating properties and the possibility of precise machining are further advantages that are particularly associated with PVE.

[0017] Alternatively or additionally, temperature-assisted expansion of the inner formwork can be provided by configuring the plastic inner formwork such that a temperature increase within the inner formwork causes it to expand. Providing a formwork core in a formwork configuration with the largest possible component dimensions can result in a comparatively large dimensional difference between the formwork configuration and the removal configuration. This simplifies removal, among other things, because even slight positive and / or negative deviations from an ambient temperature can be sufficient to cause adequate contraction for the removal configuration. Where contraction is discussed below, expansion is also included within the meaning of the invention, unless expansion is technically or expressly excluded.

[0018] According to one embodiment, for example, the support structure may be made essentially of plastic and be designed to follow the contraction of the inner formwork.

[0019] The support structure serves primarily to bear the weight of the inner formwork and to transfer the force exerted on the inner formwork by the weight of the casting compound. The inner formwork can be mounted on the support structure, for example, in the form of a sliding bearing, in order to essentially decouple the contraction movement of the inner formwork from the support structure. Alternatively or additionally, coupling points can be provided at which the inner formwork is essentially intolerant of movement and connected to the support structure. For such coupling points in particular, it can be provided that the support structure essentially comprises a thermoplastic material, especially in the type and / or proportion of the material used in the inner formwork.Consequently, in addition to the temperature reduction effective in the inner formwork, a temperature reduction effective in the support structure can also be provided, which likewise causes contraction and thus preferentially follows the contraction of the inner formwork. In this way, unintended deformations of the inner formwork or damage to the formwork core can be avoided.

[0020] According to a further development, it can optionally be provided that the support structure has a number of ribs which are designed to be multi-layered, at least in sections.

[0021] In other words, several elements, particularly plate-like elements preferably connected by adhesive bonding and / or screwing, can form a common support rib. Plate-like plastic elements are readily available on the market and can be easily procured for the intended support structure. Advantageously, individual elements of the support ribs can have a conical longitudinal cross-section. Multi-layered support ribs represent a particularly inventive development with independent inventive value.

[0022] Furthermore, in one embodiment it can be provided that preferably a plurality of mutually abutting formwork elements form the inner formwork, in particular that a number of side formwork elements, ceiling formwork elements and / or floor formwork elements form the inner formwork, wherein preferably at least two formwork elements are connected to each other along a joint in a substantially casting-tight manner.

[0023] Particularly for the production of large-format hollow bodies, it may be necessary, according to a specific embodiment, for the inner formwork to have formwork surfaces that preferably define a cuboid shape, with two formwork surfaces forming two opposing outer surfaces of the cuboid shape. This allows the production of components that have a cavity closed in several spatial directions, particularly in five spatial directions. Preferably, the formwork surfaces do not form any demolding slopes; in particular, the formwork surfaces should be aligned parallel to each other in the demolding direction. This allows the production of hollow bodies with parallel walls.

[0024] In a further development, it may be provided that, in particular, a first formwork element is screwed to a second formwork element.

[0025] Bolting two abutting formwork elements together, preferably using countersunk screws or similar fasteners, provides a particularly simple and secure connection method. Furthermore, a force-fit or form-fit connection is especially advantageous because it prevents the introduction of significant stresses into the formwork elements, unlike the material-bonded connections such as welding. Initial non-public tests have shown that such stresses can influence temperature-induced deformation behavior, potentially impairing the dimensional accuracy of the formwork.

[0026] For example, a seal, preferably made of an elastomeric material, can be particularly advantageous in the area of ​​the joint, regardless of the specific design of the connection technology. An additional seal can reduce or prevent the unintentional leakage of casting compound, which is especially effective in conjunction with a screw connection, since the clamping forces can be adjusted by means of the screw.

[0027] Furthermore, a bolted connection is advantageous because it allows for relative movement between the formwork elements, particularly translational movement, to compensate for possible, sometimes very slight, differences in contraction between the formwork elements. This can be achieved by incorporating a number of elongated holes, enlarged bores, and / or similar features in the formwork elements, allowing the bolt shank to have movement tolerances within the elongated hole or bore.

[0028] In a further development, it may be provided that, for example, the inner formwork comprises at least five side formwork elements, wherein four side formwork elements are aligned parallel to a demolding direction and a fifth side formwork element is aligned transversely to it, wherein preferably each of the four side formwork elements is connected to two further of the four side formwork elements in a substantially casting-tight manner, and wherein in particular the fifth side formwork element is connected to each of the four further side formwork elements in a substantially casting-tight manner.

[0029] Hollow bodies designed as space-creating, (quasi-)monolithic building elements such as modular units, garages, or the like are prefabricated and serially manufactured under appropriately controlled conditions. Rectangular shapes are typically required, which necessitates the avoidance of draft angles. The conventional formwork process for this typically takes several hours, and the formwork devices used are, as previously described, mechanically very complex. In a further development, the formwork core can therefore advantageously have at least five side formwork elements, with three side formwork elements each serving to form one side wall of the hollow body and two further side formwork elements serving to form the ceiling and floor, respectively.

[0030] Preferably, side formwork elements can be arranged between a ceiling formwork element and a floor formwork element.

[0031] The present invention is based on the idea of ​​significantly simplifying the technical complexity of known formwork cores. The use of an inner formwork made primarily of thermoplastic material allows for a near-complete elimination of complex hydraulic or pneumatic formwork systems, which offers the following advantages: ▪ First, acquisition costs can be reduced, as the procurement costs of the proposed inner formwork or formwork elements are lower than those of the aforementioned known systems. ▪ Second, initial findings from prototypes suggest that the maintenance effort associated with the invention is significantly lower than with known systems. In particular, smaller quantities of operating materials, such as hydraulic fluid, lubricants, or similar substances, are required. ▪ Third, a formwork core according to the invention is significantly lighter, so that the resulting increase in mobility opens up new fields of application, for example, on-site formwork on the construction site or formwork in certain regions that are difficult or costly to reach for heavy transport.Fourth, the initial prototypes demonstrate that handling a mold core is simplified, as no folding, collapsing, and / or disassembly mechanisms are required for demolding. This reduces the knowledge and training requirements of the operator and accelerates instruction. Fifth, the proposed approach essentially eliminates the need for draft angles.

[0032] Particularly when used according to the invention in developing countries or disaster areas, the described measures can make a significant contribution to providing (new) living or shelter space quickly and easily by means of hollow bodies in the form of room modules or the like.

[0033] According to one embodiment, it can be provided that the wall thickness of the inner formwork, in particular the wall thickness of a formwork element, is preferably at least 15 mm in some sections, preferably between 15 mm and 40 mm, and particularly preferably between 20 mm and 30 mm.

[0034] Internal tests have shown that formwork wall thicknesses of the aforementioned dimensions, in particular a wall thickness of 25 mm, can form a temperature-induced contraction and / or expansion of the inner formwork, which is sufficient for a desired removal or formwork configuration and at the same time forms a sufficiently load-bearing inner formwork.

[0035] Furthermore, a more detailed embodiment is possible, according to which, for example, the inner formwork has a first formwork element and a second formwork element, wherein the first formwork element has a first wall thickness and the second formwork element has, at least in some areas, a second wall thickness that differs from the first.

[0036] Preferably depending on the formwork requirements, for example regarding the load-bearing capacity of the inner formwork, the extent of the intended contraction or expansion and / or the intended formwork weight, an inner formwork can, for example, have one or more formwork elements.

[0037] Furthermore, it may be provided that a formwork element is essentially a single piece or that several parts form a formwork element. Particularly for large-format formwork elements, it can be advantageous to join several parts together to form a single formwork element, for example, to reduce acquisition costs. Multiple parts are also logistically practical, as special transports requiring permits can be avoided. Alternatively or additionally, for example, inner formwork, formwork elements, and / or formwork element components may have differing wall thicknesses. These wall thickness differences can exist between several formwork elements and / or formwork element components. Likewise, areas with different wall thicknesses may be provided within a single formwork element or formwork element component.These possible adjustments allow, for example, application-specific increases in load-bearing capacity through increased wall thickness, while areas with reduced wall thickness can contribute to a reduced overall weight or optimized weight distribution. Areas of varying wall thicknesses within a number of formwork elements and / or formwork element components can be created, for example, by milling for selective material removal or similar processes.

[0038] Furthermore, a targeted design of the wall thickness has proven particularly advantageous with regard to thermal properties, as a narrow inner formwork can release a quantity of heat earlier or faster, and thus contract, than wider wall thicknesses.

[0039] Preferably, a temperature control device with a number of energy transfer elements, which are effectively connected to the inner formwork, can be provided according to a further development.

[0040] Demolding a hollow body as early as possible is preferred to increase formwork utilization and thus productivity. A casting compound in the form of a hollow body should only be demolded once it has reached sufficient inherent strength and is manageable. In theIn the technical field of concrete materials, this minimum level of inherent strength is referred to as green strength. Accordingly, process optimization can be achieved through time-optimized contraction immediately after reaching sufficient inherent strength. For this purpose, a temperature control system can be used, for example, to regulate the timing and extent of the contraction of the inner formwork, which is induced by a reduction in temperature.

[0041] The temperature control device can effect a temperature change, particularly with a number of energy transfer elements in the inner mold, specifically an increase in temperature for expansion and / or a decrease in temperature for contraction. For example, energy transfer elements made of metal or the like can be provided, which are temperature-controlled and preferably in direct contact with the inner mold to create a substantially conductive heat transfer. Likewise, the energy transfer elements can, for example, include a convective, media-based heat flow for energy transfer. Furthermore, energy transfer elements can, for example, include a radiation source to enable essentially contactless heat transfer. The described energy transfer methods can be implemented individually or in any combination.

[0042] In one embodiment, it may be provided that, for example, a number of energy transfer elements have a fluid line, wherein a fluid line runs at least partially within the inner formwork and / or adjacent to the inner formwork. In this context, an arrangement is considered adjacent if, during energy transfer, the distance-related energy loss is less than 50%. Initial tests have shown that "adjacent" includes an outer distance of less than or equal to 50 cm, preferably less than or equal to 25 cm.

[0043] For a fluid line running within the inner formwork, the inner formwork can, for example, have a number of cavities that allow the fluid line to pass through. Alternatively or additionally, the number of cavities can effectively create the fluid line through which it flows, without requiring an additional fluid line in the form of a pipe and / or hose. Particularly advantageously, the fluid lines can be supplied with temperature control fluids designed to transport heat energy to the inner formwork for expansion and / or to dissipate heat energy from the inner formwork for contraction. Preferably, a plurality of fluid lines are provided. Preferably, the fluid line is designed to be fluid-tight, with the exception of one fluid inlet. This prevents contact between the fluid and the casting compound.

[0044] Preferably, the minimum dimension of the formwork core is at least two meters. This ensures that a sufficiently large demolding gap is created by contraction of the inner formwork, and the formwork core is suitable for the production of space-defining building elements, room modules, garages, and similar structures.

[0045] According to a second aspect, the invention relates to a formwork device for producing a hollow body from a casting compound, wherein the hollow body has at least one extraction opening, comprising a formwork core with a contractible inner formwork wall, referred to as the inner formwork, and an outer formwork wall, referred to as the outer formwork, wherein the inner formwork and outer formwork define a casting chamber which essentially corresponds to the geometry of the hollow body, wherein the formwork core can have a number of the features described above and below, individually or in combination.

[0046] The outer formwork can preferably be a conventional mold assembled from panels, which is disassembled or lifted off for demolding. Alternatively or additionally, it can be provided that the hollow body is removed from the outer formwork after hardening. The formwork core can, for example, be held (suspended) within the outer formwork by spacers, particularly made of a casting compound.

[0047] Preferably, the casting chamber can be box-shaped, in particular with a bottom and preferably walls perpendicular to the bottom, preferably three walls. This makes it suitable for the production of box-shaped hollow bodies.

[0048] In a preferred embodiment, the formwork device may be oriented in a horizontal position, such that the extraction opening opens essentially in a horizontal direction.

[0049] In particular, the elasto-mechanical properties of a hollow body are significantly influenced by the distribution of the casting material within the casting chamber, or rather by the distribution of the components of the casting material during the formwork process. It has been shown that a horizontally oriented formwork system, that is, a formwork system that is essentially horizontal with respect to the longitudinal axis of the hollow body during the formwork process, has a positive effect on these properties.

[0050] Another aspect of the invention relates to a method for producing a hollow body from a casting compound, wherein the hollow body has at least one extraction opening, comprising the following steps: providing a formwork device with an outer formwork and a formwork core having an inner formwork, wherein the outer formwork and inner formwork define a casting chamber, filling the casting chamber with a casting compound, at least partially hardening the casting compound, contracting the inner formwork by means of a temperature reduction effective in the inner formwork, and removing the formwork core through the extraction opening.

[0051] Preferably, the formwork core can be removed from the hollow body essentially in a horizontal direction, i.e., in this case, for example, pulled out. The demolding of the outer formwork can take place before or after the removal of the formwork core.

[0052] In a preferred further development, it can be provided that a fluid is directed to the inner formwork during the curing of the casting compound, wherein the fluid in particular has a temperature that is lower than an instantaneous temperature of the casting compound during setting, such that the contraction of the inner formwork is supported by the temperature reduction.

[0053] Active cooling with coolants, especially (cooling) fluids, can accelerate contraction, for example, by extracting heat energy from the inner formwork. Furthermore, this allows precise control of the point in time at which a removal configuration is established, specifically after sufficient contraction of the inner formwork.

[0054] It may be advantageous for the process to further include, for example: expanding the inner formwork by means of a temperature increase effective in the inner formwork.

[0055] The inner formwork can expand before, during, and / or after filling. Expansion can also occur during the setting process. However, this latter expansion is only possible as long as the casting material is sufficiently deformable or displaceable, meaning that the degree of hardening of the casting material has not yet exceeded a certain limit. For example, deformation or displacement of a hardening concrete material is no longer possible once it has reached the previously described green strength.

[0056] According to a preferred further development, it can be provided that heat energy generated during the hardening of the casting compound is used to increase the temperature.

[0057] The hardening of a casting compound is regularly associated with heat generation due to the reaction process. For example, it is known that concrete materials develop a so-called heat of hydration during hardening, which, for instance, can be 20 K higher after two to three hours of formwork than the temperature of the casting compound at the beginning of the formwork process, i.e., when filling the casting chamber of a formwork device. The increasing temperature acting within the inner formwork can cause it to expand, thus reducing the size of the casting chamber over the expansion period and displacing and / or compressing the concrete material within it. Utilizing the heat of hydration is particularly advantageous because, ideally, no external heat energy input is required. This makes the process particularly resource-efficient.

[0058] In one embodiment, it may be provided that, optionally, a fluid is directed to the inner formwork before and / or during the filling of the casting chamber and / or during the hardening of the casting compound for the purpose of expansion, wherein the fluid in particular has a temperature that is higher than a temperature of the casting compound when the casting chamber is filled.

[0059] For example, in combination with the previously described use of reaction-induced heat generation, or alternatively, active temperature control of the inner mold can be achieved, for instance, by means of a temperature control fluid that is directed to the inner mold. Fluid temperatures comparatively higher than the casting compound temperature can be used to cause expansion of the inner mold until the casting compound no longer permits further deformation or expansion within the casting chamber. Alternatively or additionally, a temperature control fluid can be used to cool the inner mold by introducing a fluid whose temperature is lower than the current temperature of the inner mold. The decreasing temperature of the inner mold causes it to contract, allowing the inner mold or a mold core to be removed without damage.Water and / or steam can be used as the fluid particularly easily, as water is environmentally friendly, regularly available and contact with the casting compound, for example with a concrete material, is not critical after partial hardening.

[0060] Active temperature control is advantageous because, firstly, it allows for or increases the expansion of the formwork core, resulting in a greater cross-sectional difference between the removal configuration and the formwork configuration. This enables non-destructive removal. Secondly, the adjustment of a removal configuration can be carried out more quickly, thus reducing process times.

[0061] For example, a radiation source can be advantageously used, the rays of which are directed at the inner formwork. Infrared radiation, for instance, can be used to heat the inner formwork and thus cause it to expand. Radiation-based methods are particularly easy to install or retrofit.

[0062] The process can be supplemented, for example, by a step in which the outer formwork is removed after the casting compound has at least partially hardened. The removal of the formwork core can take place before, during, or after the removal of the outer formwork.

[0063] The process is preferably carried out with a concrete material which releases heat of hydration when curing, whereby an expansion of the inner formwork occurs due to this heat of hydration according to the process.

[0064] It may be particularly advantageous to provide that, in particular, a previously described formwork device, e.g. according to claim 11, preferably with a formwork core of the type described above and below, is used within the framework of the proposed method.

[0065] Another aspect of the invention relates to a hollow body, in particular a concrete hollow body, preferably in the form of a space cell, which is produced by means of a method of the type described, in particular according to a method of claims 12 to 15.

[0066] These design features can be implemented in connection with the invention or be independently inventive, and they can be implemented either individually and independently of each other or in any combination, including the implementation of all the aforementioned features, unless a combination is expressly or technically excluded.

[0067] Further features, details and advantages of the invention will become apparent from the wording of the claims and from the following description of exemplary embodiments with reference to the purely schematic drawings, whereby individual features or a combination of features of the illustrated exemplary embodiments may also be realized independently of the other configuration. The drawings show: Fig. 1 a front view of a formwork core; Fig. 2 a sectional view along the Fig. 1section line AA shown; Fig. 3 a sectional view along the in Fig. 1 Section line BB shown; and Fig. 4 an overview of a manufacturing process.

[0068] Fig. 1 The figure shows, in a front view, a formwork core 1 of a formwork device in formwork configuration, such that the casting compound, here a concrete material B, which creates a hollow body 2, is in direct contact with the inner formwork 10 of the formwork core. For illustrative reasons, an outer formwork of the formwork device is not shown, which together with the inner formwork 10 defines a casting chamber that essentially corresponds to the geometry of the hollow body 2 to be produced.

[0069] The inner formwork comprises four formwork elements 11: two side formwork elements 12, one slab formwork element 13, and one slab formwork element 14. The slab and slab formwork elements 13 and 14 are each connected to the side formwork elements 12, with the joints of the formwork elements 11 being sealed to prevent the casting compound from leaking and designed such that the side formwork elements 12 are positioned between the slab and slab formwork elements 13 and 14, respectively. Countersunk screws (not shown) create a permanent connection at the joints. The side formwork elements 12, the slab formwork element 13, and the slab formwork element 14 define a cuboid shape without forming any significant demolding slopes. Rather, the formwork elements 11 are parallel to the demolding direction ER ( Fig. 2 ) aligned.

[0070] The formwork device is oriented horizontally, so that the extraction opening 20 of the hollow body 2 opens essentially in a horizontal direction.

[0071] In the illustrated embodiment, the side formwork elements 12, the ceiling formwork elements 13, 14 preferably each comprise four formwork elements 11, wherein the formwork elements 11 are made of polyvinyl ether and have a wall thickness of 25 mm. The side formwork elements 12 are each 3490 mm long and 2500 mm wide. The ceiling and floor formwork elements 13, 14 are each 3490 mm long and 1800 mm wide.

[0072] If the temperature acting on the inner mold 10 decreases, the inner mold 10 contracts into a removal configuration, causing the inner mold 10 to detach from the hollow body 2 and creating a demolding gap. The demolding gap formed is sufficient to allow the mold core 1 to be removed non-destructively in the demolding direction ER through the removal opening 20.

[0073] Furthermore, in Fig. 1A rib-like support structure 15 can be seen, which supports the inner formwork 10 and also consists essentially of polyvinyl ether. The side ribs 16, arranged upright along the side formwork elements 12, have side rib elements 16k that are conical in longitudinal cross-section and taper from the bottom formwork element 14 towards the top formwork element 13. Top and bottom ribs 17, 18 comprise top and bottom rib elements 17e, 18e, respectively, and are essentially the same length, with some bottom rib elements 18h being significantly wider or taller than the top ribs 17. Overlapping rib sections are shown by dotted lines.

[0074] A cross-sectional view along the in Fig. 1 The depicted section line AA shows Fig. 2The second side formwork element 12 is not shown for illustrative purposes. The ceiling and floor formwork elements 13 and 14 are in direct contact with the concrete material B of the hollow body 2. The formwork core 1 can be removed in a removal configuration in a substantially horizontal demolding direction ER.

[0075] The formwork elements 11 and the inner formwork 10 are supported by a multi-layered support structure 15. Elements of the slab ribs 17 and the floor ribs 18 interlock with elements of the side ribs 16, creating a particularly rigid, interlocking support structure 15. The side ribs 16 each have two conically shaped side rib elements 16k with a length of 2500 mm, so that these side rib elements 16k abut directly the slab and floor formwork elements 13, 14. In contrast, further side rib elements 16e rest on floor rib elements 18e, in particular the tall floor rib elements 18h, or connect to slab rib elements 17e.

[0076] Several rib elements 16a, 16k, 17e, 18e, 18h are connected to each other in a lamellar fashion by means of bolts 19. All rib elements 16a, 16k, 17e, 18e, 18h have a uniform wall thickness of 25 mm. Furthermore, the support structure 15 exhibits the same contraction behavior as the inner formwork 10, which is particularly beneficial for extended service life.

[0077] A cross-sectional view along the in Fig. 1 The depicted section line BB shows Fig. 3 The bottom formwork element 14 is not shown for illustrative purposes. The side formwork elements 12 are in direct contact with the concrete material B of the hollow body 2.

[0078] A ceiling rib 17 essentially comprises a ceiling rib element 17e, to which four conical side rib elements 16k are laterally connected via rib flanks, and which abuts directly at its ends the side formwork elements. The rib elements 16a, 16k, and 17e are connected to each other by means of bolts 19.

[0079] Fig. 4Figure 100 shows the process of an exemplary method 100 for producing a hollow body 2 from a casting compound. First, a formwork device with an outer formwork and a formwork core 110 comprising an inner formwork 10 is provided, wherein the outer formwork and inner formwork 10 define a casting chamber. The casting chamber is then filled with a casting compound 120, in particular with a concrete material B. Before filling, reinforcements are regularly placed in the casting chamber and suspended. After filling 120, the casting compound is allowed to harden at least partially 130, to a degree of hardening at which the hollow body 2 can be handled essentially monolithically. After reaching a sufficient degree of hardening, the inner formwork 10 is contracted 140 by means of a temperature reduction effective in the inner formwork 10.The contraction 140 creates a removal configuration in which the formwork core 1 has a smaller cross-section than in a formwork configuration, in particular a formwork configuration at the time of filling 120. Subsequently, the removal 150 of the formwork core 1 takes place through the removal opening 20 of the hollow body 2 in the demolding direction ER.

[0080] As previously explained, during the curing process of the concrete material B, heat of hydration is released, which acts on the inner formwork 10 and causes it to expand. After reaching a culmination point, at which the inner formwork 10 has expanded to its maximum extent, it can be actively cooled, for example, using a cooling fluid. Cooling the inner formwork 10 supports contraction and, firstly, accelerates the curing process of the concrete material B and, secondly, reduces the process time until the extraction configuration is reached.

[0081] The invention is not limited to one of the embodiments described above, but can be modified in many ways.

[0082] All features and advantages arising from the claims, the description and the drawing, including design details, spatial arrangements and process steps, can be essential to the invention both individually and in various combinations. Reference symbol list

[0083] 1 Formwork core 2 Hollow body 10 Inner formwork 11 Formwork element 12 Side formwork element 13 Ceiling formwork element 14 Bottom formwork element 15 Support structure 16 Side rib 16e Side rib element 16k Conical side rib element 17 Ceiling rib 17e Ceiling rib element 18 Bottom rib 18e Bottom rib element 18h High bottom rib element 19 Bolt 20 Removal opening 100 Manufacturing process 110 Providing a formwork device 120 Filling the casting chamber 130 Curing the casting compound 140 Contracting the inner formwork 150 Removing the formwork core B Concrete material ER Demolding direction

Claims

1. Formwork core (1) for producing a hollow body (2) from a casting compound, wherein the hollow body (2) has at least one extraction opening (20), comprising ▪ an inner formwork wall designated as inner formwork (10), ▪ and a support structure (15) supporting the inner formwork (10), wherein the inner formwork (10) is designed to be contractible, such that the formwork core (1) has a smaller cross-section in an extraction configuration than in a formwork configuration, characterized by that the inner formwork (10) essentially comprises a thermoplastic material and is designed such that a temperature reduction effective in the inner formwork (10) causes the inner formwork (10) to contract, such that the formwork core (1) can be removed from the hollow body (2) in the removal configuration through the removal opening (20) without damage.

2. Formwork core (1) according to claim 1, characterized by thatthe support structure (15) is essentially made of plastic and is designed to follow the contraction of the inner formwork (10).

3. Formwork core (1) according to claim 1 or 2, characterized by that the supporting structure (15) has a number of ribs (16, 17, 18) which are designed to be multi-layered at least in sections.

4. Formwork core (1) according to one of the preceding claims, characterized by that a plurality of mutually abutting formwork elements (11) forms the inner formwork (10), in particular that a number of side formwork elements (12), ceiling formwork elements (13) and / or bottom formwork elements (14) form the inner formwork (10), wherein at least two formwork elements (11) are connected to each other along a joint in a substantially casting-tight manner.

5. Formwork core (1) according to claim 4, characterized by that a first formwork element (11) is screwed to a second formwork element (11).

6. Formwork core (1) according to claim 4 or 5, characterized by that the inner formwork (10) comprises at least five side formwork elements (12), wherein four side formwork elements (12) are aligned parallel to a demolding direction (ER) and a fifth side formwork element (12) is aligned transversely thereto, wherein each of the four side formwork elements (12) is substantially sealed against casting compound with each of the other two of the four side formwork elements (12), and wherein the fifth side formwork element (12) is substantially sealed against casting compound with each of the four other side formwork elements (12).

7. Formwork core (1) according to one of the preceding claims, characterized by that the wall thickness of the inner formwork (10), in particular the wall thickness of a formwork element (11), is at least 15 mm in at least sections, preferably between 15 mm and 40 mm, and particularly preferably between 20 mm and 30 mm.

8. Formwork core (1) according to one of the preceding claims, characterized by that the inner formwork (10) comprises a first formwork element (11) and a second formwork element (11), wherein the first formwork element (11) has a first wall thickness and the second formwork element (11) has at least in some areas a second wall thickness that differs from the first.

9. Formwork core (1) according to one of the preceding claims, characterized by a temperature control device with a number of energy transfer elements which are connected to the inner formwork in an energy transfer-effective manner (10).

10. Formwork core (1) according to claim 9, characterized by that a number of energy transfer elements have a fluid line, wherein a fluid line runs at least partially within the inner formwork (10) and / or adjacent to the inner formwork (10).

11. Formwork device for producing a hollow body (2) from a casting compound, wherein the hollow body (2) has at least one extraction opening (20), comprising ▪ a formwork core (1) with a contractible inner formwork wall, referred to as the inner formwork (10), ▪ and an outer formwork wall, referred to as the outer formwork, wherein the inner formwork (10) and the outer formwork define a casting chamber which substantially corresponds to the geometry of the hollow body (2), characterized by that the formwork core (1) is designed according to one of the preceding claims, wherein the formwork device is preferably oriented in a horizontal position, such that the removal opening (20) opens substantially in a horizontal direction.

12. Method (100) for producing a hollow body (2) from a casting compound, wherein the hollow body (2) has at least one extraction opening (20), comprising the following steps: ▪ Providing (110) a formwork device with an outer formwork and a formwork core (1) having an inner formwork (10), wherein the outer formwork and inner formwork (10) define a casting chamber, ▪ Filling (120) the casting chamber with a casting compound, ▪ At least partially hardening (130) the casting compound, ▪ Contracting (140) the inner formwork (10) by means of a temperature reduction effective in the inner formwork (10), ▪ Removing (150) the formwork core (1) through the extraction opening (20).

13. Method (100) according to claim 12, characterized by thatDuring the curing (130) of the casting compound, a fluid is directed to the inner formwork (10), the fluid having a temperature lower than the instantaneous temperature of the casting compound during curing (130), such that the reduction in temperature supports the contraction (140) of the inner formwork (10).

14. Method (100) according to claim 12 or 13, characterized by that the method (100) further comprises: ▪ Expanding the inner formwork (10) by means of a temperature increase effective in the inner formwork (10), wherein heat energy generated during the curing (130) of the casting compound is preferably used for the temperature increase.

15. Method (100) according to claim 14, characterized by thatFor expansion, a fluid is directed to the inner formwork (10) before and / or during the filling (120) of the casting chamber and / or during the curing (130) of the casting compound, wherein the fluid has a temperature that is higher than a temperature of the casting compound during the filling (120) of the casting chamber.

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