Accessory for creating recesses and cutting for prestressing.

Description

1 / 8 Accessory for creating recesses and cutting for prestressing. UTILITY MODEL FIELD

[001] This utility model refers to a device applied in civil construction, more specifically to the execution of prestressed slabs. The device is intended to be positioned on the edge of the slab during concreting, creating an adequate space for cutting the excess end of the strand using grinders or similar tools after tensioning. BACKGROUND OF THE UTILITY MODEL

[002] Prestressed slabs with greased strands constitute a structural system widely used in modern civil construction. Unlike conventional slabs, which use only passive reinforcement to resist stresses, prestressed slabs incorporate high-strength steel strands that, after being tensioned, introduce prior compressive stresses into the concrete. This procedure reduces cracking, increases the ability to span large distances, and allows for thinner slabs with lower concrete and steel consumption.

[003] The construction process of a prestressed slab begins with the assembly of conventional distribution and reinforcement bars. Next, greased strands, encapsulated in plastic sheaths, are arranged through the slab according to the prestressing design. These elements are fixed in defined positions, passing through devices that regulate their height and being anchored to specific pieces located at the ends of the slab. After the assembly of the reinforcement, strands, and accessories, the side panels are installed and the anchoring pieces are positioned. Once this stage is completed, the slab is concreted, completely covering the system.

[004] At the ends of the slab are found fundamental components for the performance of the prestressing. The reinforcement cage, positioned next to the anchorages, acts in the confinement of the concrete and in the control of cracking. Petition 870250086876, dated 09 / 25 / 2025, page 23 / 37 2 / 8 located. Anchorages, in turn, can be active or passive: active anchorage is that by which the prestressing force is applied with hydraulic jacks, while passive anchorage functions as a reaction point, receiving the forces transmitted by the strand. In both cases, an anchorage wedge is used, an element responsible for mechanically securing the steel wires and ensuring the safe transfer of forces.

[005] Another essential element is the prestressing niche, a space formed in the active anchorage region that allows subsequent access for tensioning operations, cutting of excess strands, and sealing with grout. Only after concreting and reaching the minimum concrete strength specified in the project does the tensioning phase of the strands begin. Once this procedure is completed, the need arises to treat the excess end of the strands, an operation that involves cutting and finishing them, a step in which the solution proposed in this patent is inserted.

[006] The state of the art reveals that, for the formation of prestressing niches, accessories of predominantly truncated cone shape are used, provided with nozzles centered on each of their faces (upper and lower), which receive a through hole intended for the entry of the strand. These accessories, known as pocket formers, are removed after concreting, leaving a cavity of the same shape that allows the tensioning of the strands by means of the prestressing jack. During assembly, a sealing element or adhesive tape is also usually used between the pocket former and the retaining panel, in order to prevent the concrete from flowing through the strand passage hole.

[007] The patent document that represents the state of the art closest to that described in the paragraph above is US patent US10633861B2 which reveals exactly the elements used to create the prestressing recess and its shape after concreting.

[008] After prestressing, the excess strands are cut off. Petition 870250086876, dated 09 / 25 / 2025, page 24 / 37 3 / 8 Technical standards and best practices establish that this cut must be made at least 20 mm into the niche and, in cases where tools that generate high temperatures are used, a minimum distance of 20 mm must be maintained in relation to the anchoring wedge.

[009] The most commonly used method today is the use of a blowtorch, due to its cutting speed. However, this process has logistical disadvantages, as it requires the availability of specific equipment and specialized labor.

[0010] Other known solutions include the use of plasma cutters and hydraulic guillotines. These tools, due to their dimensions and handling characteristics, allow the cutting to be carried out properly and safely.

[0011] Despite this, the solutions mentioned above have some obstacles to their implementation. Plasma cutting generates very high temperatures, capable of damaging the plastic encapsulation, deforming metal rings and compromising seals, as well as affecting the fixation of wedges and cables if the region is hit. The process also requires specialized labor and involves risks inherent to its use. Furthermore, it depends on specific equipment, such as adapted pocket formers, resulting in significantly higher costs.

[0012] As for guillotine or hydraulic shear cutting, it is possible to eliminate heat-related problems, offering greater precision and allowing for sectioning at appropriate lengths without requiring highly specialized labor. However, this is imported equipment, with a high acquisition cost and expensive operation, since the knives or blades, made of special alloys, suffer significant wear when cutting wire ropes, requiring frequent replacements and costly maintenance.

[0013] As an alternative to the processes described above, cutting with abrasive tools, such as sanders, grinders or similar tools, stands out, which, although somewhat slower, represent a low-cost and higher-quality solution. Petition 870250086876, dated 09 / 25 / 2025, page 25 / 37 4 / 8 logistical simplicity, enabling execution by conventional construction teams. However, the reduced diameter of the niche makes proper tool positioning difficult, compromising the necessary setback into the structure. Consequently, the cut is made flush with the lateral surface of the slab, a practice that fails to meet technical standards and good execution practices, as it does not respect the minimum cover and does not allow for proper sealing of the niche, either with caps containing protective greases and grout, or with prefabricated elements intended for closing the niche.

[0014] Given these limitations, there is a need to develop improvements capable of optimizing the wire rope cutting process, providing greater efficiency and safety, without relying on complex, expensive tools or those requiring highly specialized labor. SUMMARY OF THE UTILITY MODEL

[0015] This utility model refers to an ACCESSORY FOR FORMING A NICHE AND CUTTING FOR PRESTRESSING, intended to be attached to the lower (larger diameter) part of the pocket former, with the purpose of facilitating the cutting of the strands in accordance with technical standards and good construction practices.

[0016] The accessory has a trapezoidal shape, with a through hole centered on its upper and lower faces. It is fitted to the pocket former by means of its shorter (upper) face and to the retaining panel by its longer (lower) face, that is, it is positioned between the retaining panel and the pocket former. After the slab is poured, both the accessory and the pocket former are removed, resulting in a trapezoidal niche with a truncated cone hole in its center.

[0017] This trapezoidal configuration allows the use of grinders for cutting the strand to be feasible, ensuring adequate spacing between the end of the strand and the edge of the slab, which is not achieved by Petition 870250086876, dated 09 / 25 / 2025, page 26 / 37 5 / 8 known solutions.

[0018] The accessory's design also allows it to be positioned alongside others of the same type, enabling its application in areas where the cables are grouped together while respecting the recommended minimum distances between anchor points.

[0019] In an alternative model configuration, the niche forming accessory can be integrated into the pocket former in a single piece, simplifying the installation process and reducing the time required for on-site assembly.

[0020] Another alternative configuration consists of producing multiple sets, in which the accessories are manufactured already joined together to accommodate groupings of strands, and this configuration can also be associated with integrated pocket formers.

[0021] The accessory now proposed, therefore, overcomes the limitations of the state of the art by providing a prestressing niche suitable for cutting the strand, ensuring the correct spacing between the end of the strand and the edge of the slab, in addition to greater practicality and safety in the execution of the prestressing. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 shows three views of the accessory (7), demonstrating the top (2) and bottom (3) faces, through hole (1) and recess (8).

[0023] Figure 2 shows three views demonstrating examples of pocket former configurations (4) comprising nozzles (5).

[0024] Figure 3 shows an exploded view and a view already assembled on site, of the traditional system, demonstrating the cable and pocket former (4) directly fitted into the anchoring element.

[0025] Figure 4 shows an exploded view and a view already assembled on site, demonstrating the cable, the accessory (7) fitted into the pocket former (4) which Petition 870250086876, dated 09 / 25 / 2025, p. 27 / 37 6 / 8, in turn, fits into the anchoring element.

[0026] Figure 5 shows views of the side face of the slab after concreting using the traditional system, showing the recesses (10) and the strands (6) before and after cutting with an angle grinder or equivalent tool. Note that the end of the strand (6) after cutting is flush with the face of the slab.

[0027] Figure 6 shows views of the side face of the slab after concreting using the accessory (7), showing the niches (10) and the strands (6) before and after cutting with an angle grinder or equivalent tool. Note that the end of the strand (6) after cutting is recessed into the niche (10).

[0028] Figure 7 shows isometric views of the alternative configurations in which the accessory (7) has, respectively, two, three and four holes (1).

[0029] Figure 8 shows an isometric view of and a side view of the accessory (7'), demonstrating an alternative configuration in which the accessory (7) and the pocket former (4) are joined into a single piece (7'). DETAILED DESCRIPTION OF THE UTILITY MODEL

[0030] The present utility model proposes an ACCESSORY FOR FORMING A NICHE AND CUTTING FOR PRESTRESSING, consisting of a trapezoidal prism-shaped body provided with a through hole (1), centrally located and extending from its upper face (2) to its lower face (3). The accessory is coupled to the pocket former (4) by means of its upper face (2), so that the tip (5) of the pocket former passes through the aforementioned hole (1). The strand (6) is passed through this assembly, accessory and pocket former.

[0031] Although the dimensions of the accessory (7) may vary, its height, bottom angles and the length of its base must be such that they allow the cable (6) to be cut with a grinder at the appropriate recess (at least 20 mm from Petition 870250086876, dated 09 / 25 / 2025, p. 28 / 37 7 / 8 face of the concrete). The dimensional ranges foreseen are: height between 20mm and 40mm, lower length (base of the trapezoid) between 90mm and 150mm, lower angles of the trapezoid between 30° and 45°, and width between 60mm and 90mm. If these measurements are smaller, the grinder would not correctly reach the strand (6) and / or there would not be a perfect fit with the pocket former (4), allowing concrete to enter the assembly. On the other hand, dimensions larger than the established ranges would imply greater consumption of grout and could hinder the concentration of strands in grouped areas.

[0032] The lower face (3) has, around the hole (1), a preferably flat surface (9). This configuration eliminates the need for additional sealing elements. In the absence of this flat surface (9), the accessory (7) may require the use of a sealing element or adhesive tape to prevent the passage of concrete during concreting.

[0033] Another preferred feature consists of a recess (8), arranged on the upper face (2) concentrically to the orifice (1). This recess (8) assists in the fitting between the accessory (7) and the pocket former (4), in addition to providing better sealing between the parts. In the configuration where the accessory (7) does not have such a recess, the union with the pocket former (4) will occur only by fitting the nozzle (5) into the orifice (1), and may also require an additional sealing element. Furthermore, without the recess (8), the niche (10') created by the accessory (7) + pocket former (4) assembly is unnecessarily enlarged, resulting in a greater consumption of grout for sealing the niche (10').

[0034] An alternative configuration provides that the accessory (7) is manufactured already joined to others of the same type, forming a set with up to 4 holes (1) intended for the passage of the strands (6). This limitation is sufficient, since the quantity of strands (6) grouped is restricted by the construction standards.

[0035] Another possible embodiment consists of manufacturing the accessory (7) integrated into the pocket former (4) in a single piece (7'). This configuration makes its use on site more agile, as it reduces the assembly step, but Petition 870250086876, dated 09 / 25 / 2025, page 29 / 37 8 / 8 implies a more complex and costly manufacturing process.

[0036] Although the preferred form is that of a trapezoidal prism, the accessory (7) may have equivalent geometric variations, such as, for example, an oblong hemisphere with the top cut off in a plane. This alternative is considered equivalent, since it provides the same technical and functional effects in a substantially similar manner. Petition 870250086876, dated 09 / 25 / 2025, pp. 30 / 37

Claims

1 / 2 CLAIMS 1) ACCESSORY FOR FORMING A NICHE AND CUTTING FOR PRESTRESSING, characterized by having a trapezoidal prism-shaped body, provided with a central through hole (1) that extends from the upper face (2) to the lower face (3), intended for coupling, by its upper face (2), with a pocket former (4), so that the tip (5) of the latter passes through the said hole (1), allowing the passage of the strand (6); the said body of the accessory (7) having dimensions of height between 20mm and 40mm, lower length between 90mm and 150mm, lower angles of the trapezoid between 30° and 45° and width between 60mm and 90mm. 2) ACCESSORY FOR FORMING A NICHE AND CUTTING FOR PRESTRESSING according to claim 1, characterized by the accessory (7) having a recess (8), arranged on the upper face (2) in a manner concentric to the hole (1). 3) ACCESSORY FOR FORMING A NICHE AND CUTTING FOR PRESTRESSING according to either claim 1 or 2, characterized in that the accessory (7) has on its lower face (3), around the hole (1), a flat surface (9). 4) ACCESSORY FOR FORMING A NICHE AND CUTTING FOR PRESTRESSING according to any of claims 1, 2 or 3, characterized by being integrated into the pocket former (4), constituting a single body (7'). 5) ACCESSORY FOR FORMING A NICHE AND CUTTING FOR PRESTRESSING according to any of claims 1, 2, 3 or 4, characterized by being manufactured together with other identical accessories, forming a multiple module with up to 4 holes intended for the passage of grouped strands. Petition 870250086876, dated 09 / 25 / 2025, p. 31 / 37 2 / 2

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