An assembly of a recess former and a lifting strap for concreting

Abstract

Present invention relates to an assembly (3) of a recess former (1) and a lifting strap (2) for concreting and comprising the recess former (1) and a lifting loop portion (6) of the lifting strap (2) therein. Side of said recess former (1) are trapezoidal. The recess former (1) is closable by removable lid (5). On the side of the shorter bases of the side walls (4), the bottom of the recess former (1) is formed as a channel (7) tapering from the opposite ends of the recess former (1), where said channel comprises a portion (8) with smoothly curved convergent walls, which passes into a narrow portion (9) of uniform cross-section. A portion (10) of the lifting strap (2) intended for fastening and to be concreated into the concrete element exits from said narrow portion (9) of the channel (7).

Description

An assembly of a recess former and a lifting strap for concretingTechnical Field

[0001] The present invention relates to the field of construction technology and more specifically to an assembly of a recess former and a lifting strap for concreting, intended for casting into the concrete element.Background Art

[0002] Utility model of Russian Federation RU194846U1 (published 25.12.2019) relates to an assembly eyelet of textile strap for concreting, the upper part of which forms the lifting loop portion, and two tails of which intended for concreting have attached reinforcement bars for anchoring into concrete. The assembly eyelet is intended for direct casting, adapted only for posts, beams, and stairs, but does not solve lifting problems of wall panels or lateral casting. Furthermore, the strap exiting from concrete is not protected against the breaking of fibres upon the friction of hardened concrete, and also the problem of the exit aperture or the resulting angle of the strap has not been solved, which may cause damage of the strap when cut due to a sharp concrete edge.

[0003] German utility model DE7541863U (published 08 / 07 / 1976) relates to an assembly of a recess former and lifting cable / lifting strap for concreting. In this solution, the recess former is formed as a channel tapering from the opposite ends of the recess former, whereby the width of the channel corresponds at least to a width of the lifting cable or lifting strap. A portion of the lifting strap forming the lifting loop intended for concreting exits from the narrower portion of the recess former. The wider portion of the recess former remaining on the surface of the concrete element includes sufficient space for pressing the lifting strap into that space. This solution is lacking the portion intended for the lifting loop of the lifting strap for protecting the lifting loop portion during concreting, which can be closed, for example, with a lid. In addition, the portion of the lifting strap to be concreted, exiting the narrower portion of the recess former, is not protected – it is exposed to concrete and upon lifting the concrete element from the lifting strap, when the lifting strap stretches, the hardened concrete will break the fibres of the lifting strap exposed to concrete, thus compromising its lifting capacity.Disclosure of Invention

[0004] The present invention proposes an economical lifting system consisting of a lifting strap made of a textile strap, forming a lifting loop, and a form installation accessory, which is a recess former for concreting comprising the mentioned lifting strap. The assembly of a recess former and a lifting strap for concreting is intended for casting into the concrete element.

[0005] The assembly of a recess former and a lifting strap for concreting forms a lifting structure intended for lifting and installing concrete elements. For lifting the concrete elements, relevant lifting loops must be attached to the concrete elements. In the prior art, mainly structures based on reinforced steel with certain thickness have been used, but a system based on textile makes production and construction much cheaper, more flexible, convenient, and environmentally sustainable. Use of textile lifting straps and lifting loops formed of such straps instead of metal loops is several times more environmentally sustainable, because it minimises carbon footprint.

[0006] The proposed textile lifting loop for concreting of the invention is a device cast into concrete for lifting concrete elements. The material of concrete elements can be concrete, fibrous concrete, composite or any other similar material. Concrete elements are mainly wall panels, both interior as well as exterior walls, but also latches, beams, posts, and stairs.

[0007] The lifting structure consists of a lifting strap and a protective recess former, which achieve the required functionality with mutual interaction, and enable the transport and placement of the element.

[0008] Functions of the recess former are:1) to prevent local linear loading and the resulting potential breakage of a textile strap positioned under an angle;2) to enable installation of the lifting strap to the designed location before concreting;3) to prevent penetration of concrete milk into the area of lifting loop of the strap;4) to protect the lifting strap from external impacts (UV radiation, moisture, rain, snow, ice).

[0009] The function of the lifting strap is to enable lifting up the element, taking account of its weight, for its transport and installation at a construction site. Composition of the lifting strap is based mainly on polypropylene, but also other materials with relevant strength can be used. The lifting strap may be reinforced with hydrophobic fibres and / or fibres made of stronger material (e.g. Kevlar®, aramid fibres, carbon fibres,etc).

[0010] In a preferred embodiment of the invention, the lifting strap is coated with a protective cover. The protective cover is made of polymer material.

[0011] The function of the protective cover of the lifting strap is to eliminate the stretching problem of the full extent of the strap and to provide more flexibility to the lifting strap and prevent the consolidation of the breaking point. The idea of this solution is to use mainly the attachment to the reinforcement for fixing the lifting strap in the concrete and to prevent the lateral adhesion of the lifting strap with concrete, which can damage fibres of the lifting strap upon lifting under high load.

[0012] In order to ensure a stable shape of the lifting strap, fine wires or metal yarns can be woven into the strap, which enable suitable positioning of the lifting strap into the concrete element, depending on the position of mesh, the position of mesh irons and the shape of the element (panels with windows, panels with steps or regular elements). Wires woven into the lifting strap also enable wrapping the concreting tails of the lifting strap around the reinforcement of the concrete element to ensure better adhesion and fix the tails. Wires can also be threaded into the strap or its edges.

[0013] The lifting structure is formed by casting the lifting strap into the concrete element upon its casting from the mould, whereby the lifting loop portion of the lifting strap remains outside to enable a crane to lift and transport the element.

[0014] The prices of a solution with a lifting strap based on a textile strap and the solutions with metal lifting loops are essentially different. The average price of a stainless-steel structure is 100–150 euros, the required number of which in an element is two or four, depending on the need. Thus, these elements make approximately half of the price of a concrete element. Solutions of non-stainless steel are cheaper, but at least two times more expensive than the solutions based on textile.

[0015] Approximate production price of a solution based on textile strap is currently approximately 8–15 euros.

[0016] Furthermore, the effect of environmental sustainability is achieved when using the assembly of textile lifting strap and recess former of the invention:1) production of textile causes less load to the environment than steel mining and the production of steel structures;2) steel structures are necessary only for lifting the concrete elements, they remain inside the panels and have no value, the top part is cut off, causing extra labour and load, and the elements of their upper part have no reuse potential. Moreover, the steel structure remaining inside the elements causes risk of corrosion (except for the details made of stainless steel) and therefore risk of fracturing of the elements. For that reason, use of structures / lifting loops made of non-stainless steel is prohibited in several countries (e.g. Sweden, Finland);3) there is no need for bending metal lifting loops, a bending device, and a specialist, which minimises factory costs;4) casting supports (formwork) can be reused, because there is no need for cutting special holes (saving plywood and labour costs during production);5) easier transport and less load on roads; one truck can deliver tens of times more lifting structures compared to metal units;6) saving of material, because metal solutions are usually not ready-made solutions, but instead metal bars are delivered for bending the required lifting loops in the factory, whereby approximately 20% of the metal is wasted;7) lifting loops formed of textile strap are universal and ready-made solutions, which do not need further separate processing for installation, thus minimising expenditure of time and resources.

[0017] The use of a textile lifting strap also resolves the safety issue at the site, because the lifting loops of the lifting strap will remain and do not need to be cut off (unlike metal lifting loops), and can be used for moving the panels away in the case of demolition or reconstruction of the object, if necessary. Lifting loops can also be used for ensuring safety during other activities on the roof or at the site.

[0018] Textile lifting loops are easy to install, there is no need to cut holes in moulds, which saves plywood material used for making the moulds and enables performing more casting rounds on casting supports. This in turn saves time and costs related to electricity, material, and labour force.

[0019] The lifting loops of the textile lifting straps can be installed manually into the correct position (e.g. one prong is turned straight down, while the other is turned above the door or window aperture and fixed). Metal lifting loops require additional bending, which increases necessary time and resources.

[0020] The lifting straps (lifting loops) are inserted into concrete during the casting process of the concrete element. Long concrete elements or beams have two lifting loops, while plate-shaped elements have at least four lifting loops.

[0021] Lifting systems based on textile cast into concrete enable lifting and transporting reinforced concrete elements from the factory to the site and install panels easily on the site. Unlike steel lifting loops, the lifting loops need not to be removed and are simply pressed between two concrete blocks or sealed back into the box with the lid of the recess former.

[0022] This is an economical lifting system consisting of a loop made of textile strap and a mould installation accessory.

[0023] The upper portion of lifting structure has a special recess former, due to which the quality of the lifting strap is protected from external impacts (moisture, UV radiation, freezing), and which makes lifting the elements safe and supports lift-proof fixing of the structure inside the concrete.

[0024] Thus, the invention provides an assembly of a recess former and a lifting strap for concreting, comprising the recess former and a lifting loop portion of the lifting strap located therein.

[0025] In a side view, the side walls of the recess former are trapezoidal, where the width of the recess former between the side walls corresponds at least to a width of the lifting strap.

[0026] At the side of the longer bases of the side walls, the recess former is closed with a removable lid, where under said lid in the recess former lies the lifting loop portion of the lifting strap. At the side of the shorter bases of the trapezoidal side walls, the bottom of the recess former is formed as a channel tapering out from the opposite ends of the recess former. The said channel comprises a portion with smoothly curved convergent walls, which pass into a narrow portion of uniform cross-section, where the width of the channel corresponds at least to a width of the lifting strap. The symmetry plane of the channel is perpendicular to the imaginary bottom plane of the recess former and the height of the narrow portion of the channel corresponds at least to the double thickness of the lifting strap. From the narrow portion of the channel exits a portion of the lifting strap intended to be fixed and cast into the concrete element.

[0027] The channel is cast of flexible polymer or plastic material, e.g. natural or artificial rubber. Its main purpose is to prevent direct contact of the fibres of the lifting strap with hardened concrete and to allow the fibres of the lifting strap stretch upon stretching of the lifting strap without breakage.

[0028] In a preferred embodiment of the invention, the lifting strap is covered by a protective cover. The protective cover is made, for example, of flexible cover material. Its main purpose is to prevent direct contact of the fibres of the lifting strap with hardened concrete and to allow the fibres of the lifting strap stretch upon the stretching of the lifting strap without breakage.

[0029] The protective cover may be based on polymers, both synthetic (e.g. plastic, caoutchouc and rubber, adhesives, and resins) as well as natural polymers (e.g. polyprene, cellulose, starch, natural caoutchouc,etc). The material can be organic or inorganic, such as silicones.

[0030] In a further embodiment of the invention, the portion of the lifting strap intended to be fixed and cast into a concrete element is placed into a protective shell. Preferably the protective shell and narrow portion of uniform cross-section of said channel with curved convergent walls are formed as one piece. Such solution enables using a lifting strap without a protective cover. In this solution, the portion of the lifting strap located in the protective shell is formed as an eyelet through which a reinforcement bar can be inserted.

[0031] In a preferred embodiment of the invention, the length of the narrow portion of the channel corresponds to at least 1.5 times the height of the recess former between the bottom and the lid.

[0032] In a further preferred embodiment of the invention, the portion of the lifting strap intended to be fixed and cast into a concrete element is formed as an eyelet. This eyelet can be fixed to the reinforcement before casting the concrete element, or a reinforcement bar can be inserted through the eyelet, which will be cast into the concrete element.

[0033] In a further preferred embodiment of the invention, the portion of the lifting strap intended to be fixed and cast into a concrete element is in the form of two tails to be fixed into the concrete element.

[0034] In the simplest embodiment, said tails of the lifting strap can be cast into the concrete element in sufficient length, while in the following embodiment, the tails can be connected to the reinforcement. In a further embodiment, the tails can be equipped with additional elements to improve the adhesion of the tails of the lifting strap during casting, or the tails are provided with elements (hooks, eyelets,etc) intended to be fixed to a reinforcement before casting.Brief Description of Drawings

[0035] The invention is described below with reference to the appended schematic figures, where:Figure 1 is an axonometric view of the assembly of a recess former and a lifting strap for concreting of the invention;Figure 2 is an end view of the assembly of a recess former and a lifting strap for concreting of the invention;Figure 3 is a cross-sectional view of the assembly of a recess former and a lifting strap for concreting of the invention along the line A-A of Fig 2;Figure 4 is a cross-sectional view of the assembly of a recess former and a lifting strap according to Figure 2 with the lid removed and the lifting loop portion of the lifting strap pulled out of the recess former;Figure 5 is a cross-sectional view according to Figure 2 of the recess former of the assembly of a recess former and a lifting strap for concreting of the invention;Figure 6 is partial cross-sectional view of an embodiment of the lifting strap with polymer protective cover;Figure 7 is a cross-sectional view according to Figure 3 of the assembly of a recess former and a lifting strap for concreting of the invention, where the portion of the lifting strap for concreting comprises a protective shell.Mode(s) for Carrying Out the Invention

[0036] For the sake of clarity, similar details and elements on different figures have similar reference numbers.

[0037] Figures 1 and 2 show an assembly 3 of a recess former 1 and a lifting strap 2 for concreting, comprising the recess former 1 and a lifting strap 2 located therein.

[0038] In a side view, the side walls 4 of the recess former 1 are trapezoidal and mutually parallel, whereby the width of the recess former 1 between the side walls 4 corresponds at least to a width of the lifting strap 2.

[0039] At the side of the longer bases of the side walls 4 (at the top on figures 1–3), the recess former 1 is closed with a removable lid 5, where under the said lid in the recess former 1 lies the lifting loop portion 6 of the lifting strap 2 – see Figure 3.

[0040] At the side of the shorter bases of the trapezoidal side walls 4, the bottom of the recess former 1 is formed as a channel 7 tapering out from the opposite ends of the recess former 1. The width of the channel 7 corresponds to a width of the lifting strap 2. The channel 7 comprises two main portions, one of which is fixed to the bottom of the recess former 1, and starts with a portion 8 with smoothly curved convergent walls, which pass into a narrow portion 9 of the uniform cross-section. As seen in the figures, the symmetry plane of the channel 7 is perpendicular to the imaginary bottom plane of the recess former 1.

[0041] The height of the narrow portion 9 of the channel 7 corresponds at least to a double thickness of the lifting strap 2. From this portion 9 exits a portion 10 of the lifting strap 2 intended to be cast into the concrete element. In the embodiment shown in the figures, the portion 10 to be concreted is formed as a loop, while in other embodiments not shown in the figures, the portion 10 of the lifting strap 2 intended to be cast into the concrete element exiting from the portion 9 is formed as two tails for their fixing into the concrete element. In the concrete element, these tails are fixed to a reinforcement or reinforcement mesh, or loops are formed at the tails, through which reinforcement will be inserted. The tails may also be wound around the reinforcement or to the reinforcement mesh.

[0042] Tapering channel 7 may be made of flexible plastic to allow its flexible deformation upon lifting the concrete element from the lifting loop 6 and mitigate the impact of stress on the lifting strap 2.

[0043] Figure 7 shows an embodiment where the portion 10 of the lifting strap 2 intended to be fixed and cast into a concrete element is placed into a protective shell 11 – in the embodiment shown in the figure, the protective shell 11 and narrow portion 9 of uniform cross-section of the channel 7 are formed as one piece.

[0044] The protective shell 11 enables providing stable shape to the portion 10 to be concreted and simplifies, for example, the insertion of a reinforcement bar through a loop formed in the portion 10.

[0045] The lifting strap 2 itself is preferably coated with a protective cover 12 made of flexible polymer material – see Figure 6. The protective cover 12 has two main functions – first, to protect the lifting strap 2 from damages, and second, to separate the portion of the lifting strap 2 in the narrow portion 9 of the tapering channel 7 cast into the concrete element from hardened concrete to prevent the breakage of fibres of the lifting strap 2.

[0046] The assembly of a recess former and a lifting strap for concreting is intended mainly for the production of concrete elements with lateral casting. Tails of the lifting strap are placed and fixed deep in the concrete to achieve the lifting stability of heavy concrete elements. The exit point of the lifting strap from the concrete element, i.e. the point where the lifting strap is located in the curved convergent channel portion and enters the narrow portion of the uniform cross-section of the channel, solves the cutting problem of concrete edge, i.e. it prevents the cutting of the concrete edge into the lateral surface of the lifting strap.LIST OF REFERENCE NUMBERS1 – recess former2 – lifting strap3 – assembly4 – side wall of recess former5 – lid6 – lifting loop portion of lifting strap7 – tapering channel8 – curved convergent channel portion9 – narrow portion of uniform cross-section10 – concreting portion of the lifting strap11 – protective shell of the lifting strap12 – protective cover of the lifting strap

Claims

An assembly (3) of a recess former (1) and a lifting strap (2) for concreting, comprising the recess former (1) and a lifting loop portion (6) of the lifting strap (2) located therein,characterized in thatin a side view the sides walls (4) of the recess former (1) are trapezoidal, where the width of the recess former (1) between the side walls (4) corresponds at least to a width of the lifting strap (2),where at the side of the longer bases of the trapezoidal side walls (4) the recess former (1) is closed with a removable lid (5), where under said lid in the recess former (1) lies the lifting loop portion (6) of the lifting strap (2), andwhere at the side of the shorter bases of the trapezoidal side walls (4), the bottom of the recess former (1) is formed as a channel (7) tapering out from the opposite ends of the recess former (1), where said channel comprises a portion (8) with smoothly curved convergent walls, which pass into a narrow portion (9) of uniform cross-section, where the width of the channel (7) corresponds at least to the width of the lifting strap (2) and where the symmetry plane of the channel is perpendicular to the imaginary bottom plane of the recess former (1),where the height of the narrow portion (9) of the channel (7) corresponds at least to a double thickness of the lifting strap (2), andwhere from the narrow portion (9) exits a portion (10) of the lifting strap (2) intended for fastening and to be concreated into the concrete element.Assembly (3) of a recess former (1) and a lifting strap (2) for concreting according to claim 1,characterized in that, the lifting strap (2) is covered by a protective cover (12).Assembly (3) of a recess former (1) and a lifting strap (2) for concreting according to any previous claim,characterized in that, the length of the narrow portion (9) of the channel corresponds to at least 1.5 times the height of the recess former (1) between the bottom and the lid (5).Assembly (3) of a recess former (1) and a lifting strap (2) for concreting according to any previous claim,characterized in that, the portion (10) of the lifting strap (2) intended to be fixed and cast into a concrete element is formed as an eyelet.Assembly (3) of a recess former (1) and a lifting strap (2) for concreting according to any previous claim 1 to 3,characterized in that, the portion (10) of the lifting strap (2) intended to be fixed and cast into a concrete element is in the form of two tails to be fixed into the concrete element.Assembly (3) of a recess former (1) and a lifting strap (2) for concreting according to claim 5,characterized in that, the tails of the lifting strap (2) are provided with hooks or eyelets intended to be fixed to a reinforcement before casting.Assembly (3) of a recess former (1) and a lifting strap (2) for concreting according to any previous claim,characterized in that, the portion (10) of the lifting strap (2) intended to be fixed and cast into a concrete element is placed into a protective shell (11).Assembly (3) of a recess former (1) and a lifting strap (2) for concreting according to claim 7,characterized in that, the protective shell (11) and narrow portion (9) of uniform cross-section of said channel (7) are formed as one piece.

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