ES2203730T3 - ENCOFRAR DEVICE FOR THE MANUFACTURE OF LIMITATIONS IN THE FORM OF A WALL OPENING ARCH. - Google Patents

Abstract

IN A FORMWORK DEVICE TO BUILD ARCHES IN WALLS OF WALLS WITH SUPPORT DEVICES FOR A FORMWORK HELMET (2) A CENTRAL, VERTICAL, ADJUSTABLE SUPPORT POINT (1) HAS BEEN PROVIDED BY A TELESCOPIC BRAZILIAN DEVICE, AND TWO-SIDES 3) SEPARATELY SEPARATELY FROM THE POINT (1), DISPLACABLE OR ROTATING. THE SUPPORT ARMS (3) ARE PARALLELOGRAMS BEING OR ARE FORMED OF DIFFERENT TELESCOPIC POINTS. IN THE HIGHER END OF THE POINT (1) A CHAIN IS FOUND WHICH, TOGETHER WITH THE VERTICAL POINT (1), SUPPORTS THE SUPPORT ARMS (3), WITH WHICH THE ELASTICALLY DEFORMABLE HELMET HAND COMES SUPPORTED BY ONLY THREE DEVICES SUPPORT IN THE ADJUSTED FORM AND WITH THE LIGHT OF AN ARC.

Description

Formwork device for manufacturing Arc-shaped limitations of openings in walls.

The invention relates to a device of formwork according to the preamble of claim 1, thus as with the preambles of dependent claims 22, 24, 25 and 26.

For the manufacture of arches in works of construction is usually done a wooden formwork for each arch that, in most cases, is destroyed after use or during disassembly. This means a considerable volume of Work and material.

Of the document AU-B-69 705/81 a known arc formwork device in construction sites, which can be use repeatedly, in which they are mounted so adjustable in a central hub, located inside the arch, numerous divergent support arms outward by way of radios Each support arm with an adjustable length is fixedly or orientably held at an anchor point in the flexible formwork sheet, in order to adjust different shapes and / or spans of arches and support them in formwork. The Adjustment jobs are laborious and time-consuming, since it is necessary to adjust a high number of points in the curvature of the arc that the formwork sheet encloses as a wrapping curve. The two support arms, which support the ends of the arch when this has its maximum span, they move down beyond the ends of the arch by shortening the length of the arch by modifying the in vain of it, since the formwork sheet is not mobile in the sense longitudinal in relation to the support arms.

An adjustable formwork device that can be use repeatedly, known from the document EP-A-0 136 906, has a bipartite formwork sheet whose parts are joined together by means of a hinge to be able to form ogival arches. In a bushing centrally mounted numerous arms of support, divergent outward by way of radii, whose ends free are firmly attached to the parts of the sheet formwork The hinge comprises a lever mechanism to be able to also form semicircular arches. The high number setting Support arms are laborious and time consuming.

In an adjustable formwork device, known of document DE-A-22 60 847, the One piece formwork sheet is supported by numerous adjustable length support arms that start as spokes of a bushing center clamping element. The handling of formwork device to vary the span and / or the shape of the arch is laborious and time consuming

In an adjustable formwork device for ogival arches, known from the document DE-A-23 34 020, are arranged numerous support arms in a central clamping element in bushing shape. Each support arm has a fixed point of formwork joint, adjustable in relation to the same. For lowered arches, the formwork sheet is provided with terminal sections, longitudinally movable and also supported on support arms. The device handling formwork to vary the span and / or the shape of the arch is laborious and It requires a lot of time and a special skill.

In a formwork device, known from document DE-A-195 09 078, for make curved lintels of doors and windows, the central strut It has a central support arm, adjustable up and down telescopically, which supports from below the center of a curved formwork plate. In the central strut is fixed a cross support on which support arms are located horizontal adjustable lengths that in turn carry crossbars to support the curved formwork plate. Between the central strut and the horizontal support arms are fixed on each arm of horizontal support other supports that run radially up to the formwork plate. In another embodiment, the ends of the formwork plate, configured with length variable, they are fixed by hinges on the crossbars of the horizontal support arms.

In a formwork device, known from GB-B-14 32 142, in both sides of an adjustable height section of a central strut, whose free end is inserted below the formwork sheet curved, a support arm is mounted on fixed hardware adjustable and of adjustable length whose end is joined together articulated by a hinge with the end of the sheet of formwork

The objective of the invention is to create a arc formwork device with which it is possible to manufacture quickly and exactly all types of bows normally used in construction works.

This goal is achieved through a device formwork with the characteristics of one of claims 1, 22, 24, 25 or 26.

With a formwork device according to the invention it is possible to make semicircular arches, ogival arches, carpanel arches and lowered arches with all radii, as well as symmetric and asymmetric arches. It is also possible to build vaults joining several elements.

With the same formwork device it is possible make different openings and wall thicknesses.

The support arms carry at their ends free clamping elements that are always under the angle correct with respect to the vertical strut. Through the crossbars of the parallelogram, movable in parallel, of each arm of support is always guaranteed a correct determination of the radius of All types of arches. Thanks to the possibility of moving the lower transverse support, as well as the clamping elements of the formwork sheet is possible to cover all types of arches and inclinations with the same formwork device.

With such a formwork device, which can be used with special frequency, arcs can be made with spans of 60 cm to 1.60 m without modification of the system.

Advantageously it is planned to use for the central strut a conventional steel support used Normally in construction sites.

According to the invention a sheet is fastened of appropriate formwork by means of three clamping elements, that is, above, to the left and to the right. Thanks to the fixed hold of the formwork sheet in three clamping elements and to the possibility of moving the support arms along the strut, as well as the possibility of moving the crossbar horizontal, it is possible to perform quickly and exactly any type of Arc. Due to the arrangement of the three clamping elements, no additional supports are required on the formwork sheet.

As a formwork sheet material you can Use wood, plastic or metal.

Instead of the adjustable clamping arms, configured in the form of a parallelogram according to claim 25 or claim 26 it is also possible to use support arms individual or, according to claim 24, shaped arms of scissors, as well as open parallelograms according to claim 22 connected with the strut fixed or movable. In accordance with claim 26 it is possible to fix or support the support arms at the top point of the strut. Functional versatility is achieved through the possibility of adjusting the support arms lateral and horizontal support. Due to the solicitation by traction of the lateral support arms, as a mechanism for fastening is preferably used on each side a chain conveniently sized, or an adjustable inclined arm. The different radii and spans of the arcs can also be achieved by telescoping adjustable horizontal crossbars according to claim 26.

With a formwork device according to the invention, and according to claims 22 to 26, it is possible make semicircular arches, carpanel arches and lowered arches with all radii, as well as symmetric or asymmetric arcs. As well It is possible to make vaults joining several elements.

According to the invention, the arms of support carry at its free ends tightening elements that They are under the correct angle with respect to the vertical strut. Thanks to the movable crossbars of the support arms, or the horizontal alignment of the crossbar in the case of a support individual, a correct determination of the radios of all types of arches. Due to the possibility of move the horizontal crossbar, or also the support arms, as well as to different types of clamping elements for fixing of the formwork sheet, all inclinations can be made and types of arches with the same formwork device.

As supports, supports can be used specially manufactured for this purpose, especially supports with a central guide to move the horizontal crossbar or the arms of support.

Examples of embodiment of the invention with reference to the figures in the which shows:

Fig. 1 Schematic elevation of a device formwork according to the invention.

Fig. 2 View in section through an element of upper tightening of the formwork sheet in the figure 1.

Fig. 3 View in section through an element of lateral tightening of the device formwork sheet formwork according to figure 1.

Fig. 4 Schematic view of the adjustment of the formwork device for an ogival arch.

Fig. 5 View of the inner side of the sheet formwork in the area of a clamping element.

Fig. 6, 7, 8 Schematic elevations of the device of formwork for the realization of different arches.

Fig. 9 Schematic elevation of another form of realization of the formwork device.

Fig. 10 Schematic elevation of another form of realization of the formwork device.

Fig. 11 Schematic elevation of another form of realization of the formwork device.

Fig. 12 Schematic elevation of another form of realization of the formwork device.

Fig. 13 View of an embodiment concrete formwork device.

The essential parts of the formwork device they are a vertical strut 1, a formwork sheet 2 and two arms of support 3 extending laterally from the strut 1. The formwork sheet 2 is elastic, but has its own stiffness enough to support the load of concrete or masonry applied on top of it. Appropriate materials for The formwork sheet 2 are PVC, plastics, steel or wood.

The formwork sheet 2 is held through clamping elements 4, 5 both at the top point of the strut 1 vertical as at the free ends of the support arms 3. In instead of the clamping element 4 at the top point of the strut 1 vertical could also be provided a rigid joint between the formwork sheet 2 and strut 1.

Each of the two support arms 3 is consisting of a lower cross member 6 and an upper cross member 7 which form a parallelogram together with the clamping plates 8, 9. The clamping plates 8 are fixed on the vertical strut a through a flange 10 and a clamping element 11. The upper crossbars 7 are supported on the clamping plate 8 by bolts 12.

Each lower cross member 6 is supported by the clamping plate 8 on a guide 14 in the form of a circular arc, the Guide 14 in the form of a circular arc is for example a groove.

The clamping plates 9 are fixed in the lower and upper crossbars 6, 7 by means of axes 15.

It is supported on each clamping plate rotating a base plate 16 bearing the clamping element 5 (fig. 1).

The clamping elements 4, 5 comprise according to U-shaped figures 2, 3 stirrups 17, 18 spanning the sheet formwork 2. On the side wings of the stirrups 17, 18 in shape of U are formed hooks 19, 20, directed inwards in which tension elements 21, 22 are coupled. In the elements of press 5 (fig. 3), the tensioning elements 22 are formed by a tightening bar 23 and a tightening screw 24. By turning the clamping screw 24 moves the tightening bar 23 in the direction of the bidirectional arrow in figure 3, so that it is held or release the formwork sheet 2.

In the clamping element 4 (fig. 2), the tensioning elements 21 are formed by rotating levers 25 which, through screws 26 supported on counter supports 27, they can tilt in the direction of the bidirectional arrow in figure 2, of so that the stirrup 17 is tensioned or tensioned.

By tilting the support arms is possible to make semicircular arches with different diameters or vain Figure 1 shows the formwork device fitted to form a semicircular arch.

If the base plates 16 are turned to the position represented in figure 1 with dots and strokes, the device formwork is set to form a lowered arch.

For the realization of ogival arches it is used preferably a split 2 'formwork sheet (fig. 4), fixed at the upper point of the strut 1 by means of fasteners 28, linked together in a hinge by means of an articulated joint 29.

Because the clamps 17, 18 do not protrude laterally (figures 2 and 3), the formwork device can be placed between vertically aligned formwork plates that laterally delimit the arc to be made.

Additionally, supports 30 may be provided. verticals (fig. 6) that constitute the outer limits of the arc.

In the support plates 8 it can be provided a graduated indicator plate (not shown) by which it is It is possible to adjust an exact angle of the support arms 3. Also, the formwork sheet 2 may have a scale 31, or of several scales 31, which facilitate the tilting of the arms of support 3 and, thus, the arc radius adjustment.

In figure 1, the formwork device is adjusted to form a semicircular arch, for example with a maximum vain. With dashed lines a middle arc is shown point and a carpetan arch with a smaller opening, the elements of Squeeze 5 sides are fastened in their exact angular position with with respect to the central vertical strut 1, as in the positions represented with continuous lines for the largest span.

Figure 6 shows a lowered arc, or reduced arrow arch, with large span and made with concrete in work. The vertical radius is less than the horizontal radius.

Figure 7 shows a carpetan arch, formwork with the formwork device whose support arms 3 they are facing up, the vertical radius or arrow is less than the horizontal radius.

In figure 8 a carpanel arch of in vain large, the formwork sheet 2 is in contact with the lateral limitations of the arch along a height considerable and the arrow of the bow is less than half of the vain.

Figure 9 shows another form of realization of the formwork device in which the two arms of support 3 in the central vertical strut 1 consists of one or two extendable horizontal HS arms aligned, leading in its free ends the lateral clamping elements SK or side clamping elements 5, the length of which is adjustable from telescopic shape Three clamping elements 4, 5 support the sheet of formwork 2 in a semicircular arch. As vertical support of support arms 3 are provided with adjustable chains or braces adjustable V that run obliquely from the elements of tighten 5 lateral, or horizontal HS extendable arms, respectively, to the area of the strut head 1. With lines Continuous a semicircular arch is symbolized with great vain. With dotted and dashed lines shows the device setting of formwork for a semicircular arch with a lower opening. In both positions, the side clamping elements 5 are held in their correct angular position with respect to the strut 1. As a guide length of support arms 3 along strut 1 a groove guide S may be provided in the strut 1.

In the embodiment of the device formwork according to figure 10, the support arms 3 are arms extendable SA, whose length is telescopically adjustable, which from the central vertical strut 1 run downwards obliquely and symmetrically with respect to the strut 1. The arms of support 3 are fixed on the strut 1 near the tip thereof and They have lateral clamping elements at their ends, or elements tightening SK of the formwork sheet. These arms are supported with each other, or with respect to the strut 1, through a crossbar St horizontal. With continuous lines the setting of the formwork device and formwork sheet 2 for an arc of Half point with large opening. Through dotted lines and dashes indicates the adjustment of the formwork sheet for a medium arc point with a lower opening, in both variants the correct angular position of the side 5 clamping elements with respect to strut 1. At the top point of strut 1 is provided a clamping element 4.

In the embodiment of the device formwork according to figure 11, the two support arms 3 in the central vertical strut 1 consists of crossbars 6, 7 lower and upper that intersect in the form of scissors and that are joined together in an articulated way. The inner ends of the lower crossbars 6 are fixedly articulated in a flange 10 which is part of an extensible support VS in the strut 1. The inner ends of the upper crossbars 7 are joined also articulated in a sliding support in the strut 1. The outer ends of the lower crossbars 6, 7 and upper are articulated together with a guide piece Elongated FT, approximately parallel to strut 1, which in the articulated junction point of the upper cross member 7 has a SL slot guide in which the point can slide down of articulated joint when the FT guide pieces approach the strut 1 (see figure 11). The lateral clamping element 5, or the clamping element SK of the formwork sheet, is always supported on each FT guide piece in its correct angular position with with respect to strut 1.

With continuous lines the device is represented formwork adjusted in such a way that the formwork sheet 2 forms a semicircular arch of great vain. With dotted lines and dashes the setting for a semicircular arch with a span is shown lower.

In the embodiment of the device formwork according to figure 12, the support arms 3 are constituted by crossbars 6, 7 inferior and superior to both sides of the strut 1 that form an open main parallelogram and which at their ends are rotatably connected to each other. In the common junction area of the lower and upper crossbars 6, 7 is provided a parallelogram F of smaller size guide comprising two auxiliary braces, fixed in an articulated way in one of the crossbars 6, 7 and swiveled together. The extremes interiors of the lower crossbars 6 are fixed so articulated on flange 10 or on a sliding support in strut 1. The inner ends of the upper crossbars 7 are joined jointly articulated at a point of articulation in the strut 1. In the common orientable joint of the crossbars 6, 7 lower and upper is an elongated support piece, which runs approximately horizontally with respect to the strut 1 through the guide parallelogram and has a guide linear for the junction point of the two auxiliary braces. In the support piece is mounted an extendable vertical tube VS, additionally supported if necessary by means of a crossbar in the support piece carrying the lateral clamping element 5 or the clamping element SK of the formwork sheet and keeps it in all positions always at the correct angle with respect to the strut 1.

With continuous lines the device is represented formwork adjusted in such a way that the formwork sheet 2, held at the upper point of the strut 1 by the element of press 4, form a semicircular arch with large spans, where Extensible vertical VS tubes have their shortest length. With dashed lines and strokes is symbolized for the same vain, represented with continuous lines, which by extension of expandable vertical VS tubes it is possible to form an arc carpetan Also, with dotted lines and strokes it is symbolized that, through a flatter adjustment of the open parallelogram of the 6, 7 lower and upper crossbars, an arc can be formed half a point with a smaller opening if the extensible VS tubes They are adjusted properly.

In the above embodiments, the 5 lateral clamping elements constitute support devices adjustable that, together with the clamping element 4 of the sheet formwork, determine the shape of the arch. The support arms 3 they are fixed on vertical strut 1. On each support arm 3 a clamping element 5 of the formwork sheet.

The embodiment of the device formwork according to figure 13 corresponds essentially to the form of embodiment shown in figure 1, with support arms 3 whose crossbars 6, 7 form a parallelogram together with the connecting elements or clamping plates 8, 9. On the plates of support 9 are fixed support plates 16 of the elements of tighten 5 sides. At the top point of vertical strut 1 central is the upper clamping element 4, so that the three clamping elements 4, 5 support the formwork sheet 2 above and on both sides according to the adjusted arc shape. In the strut 1 are fixed two curved crossbars, which run out and down, in a considerable part of its extension longitudinal are provided with holes of identical size whose intermediate distances grow with increasing distance from the fixation point of the curved crossbar in the strut 1. On the plate clamping 9 extends around each curved crossbar a stirrup, approximately perpendicular to strut 1, in which Find a body aligned with respect to the holes. This way it is possible, as shown in figure 13, to fix the positions of the support arms 3 in relation to the strut 1. Curved crossbars fulfill a function similar to that of adjustment chains or extendable crossbars V in the figure 9.

Claims (28)

1. Formwork device for the manufacture of limitations in the form of an arc of openings in walls, with support devices (1, 4, 5) for an elastically deformable formwork sheet (2, 2 ') comprising a strut (1) vertical center and two adjustable support arms (3), which protrude laterally on both sides of the strut (1), characterized in that each support arm (3) is provided with a lower cross member (6, 7) and an upper one which , together with the connecting elements (8,9) at their ends, constitute a parallelogram and support the formwork sheet (2, 2 ') together with the vertical strut (1). 2. Formwork device according to claim 1 characterized in that at the free ends of the support arms (3) and at the strut (1), preferably at the upper point of the strut (1), clamping elements are arranged ( 4, 5) as support devices for the formwork sheet (2). 3. Formwork device according to claim 1 characterized in that the clamping elements (5) in the support arms (3) are orientable, preferably parallel to the tilt plane of each parallelogram. 4. Formwork device according to at least one of claims 2 or 3 characterized in that the clamping elements (4, 5) comprise U-shaped stirrups (17, 18) that encompass the formwork sheet (2). 5. Formwork device according to at least one of the preceding claims characterized in that the formwork sheet (2) is provided with at least one scale (31) in the support arms (3) in the area of the elements of tightening (5). 6. Formwork device according to claim 4, characterized in that hooks (19, 20) are formed in the lateral ribs of the stirrups (19, 20) directed in which tensioning means (25, 26) can be engaged. found within the stirrups (17, 18). 7. Formwork device according to claim 3 characterized in that the clamping elements (5) are arranged in base plates (16), rotating in the connecting elements (9) around a horizontal axis. 8. Formwork device according to at least one of claims 1 to 7, characterized in that a support plate (8) is fixed on the vertical strut (1) as a connecting element for the ends of the crossbars (6, 7 ) lower and upper bearing a guide (14) in the form of a circular arc for the lower crossbar (6) of the support arm (3). 9. Formwork device according to at least one of claims 1 to 8 characterized in that the clamping element (4), placed at the top point of the strut (1), for the formwork sheet (2 '), configured preferably in a divided way, it comprises two clamping pieces (28) supported as a hinge on the strut (1) through a joint (29). 10. Formwork device according to claim 1 characterized in that the strut (1) is telescopically adjustable. 11. Formwork device according to at least one of the preceding claims characterized in that the clamping elements (5) are always in a correct angular position with respect to the vertical strut (1) during an adjustment by tilting the arms of support (3). 12. Formwork device according to at least one of the preceding claims characterized in that the lower and upper cross members (6, 7) of the parallelograms of the support arms (3) are movable in parallel to specify the radius of all types of arches, preferably by tilting the support arms (3). 13. Formwork device according to at least one of the preceding claims characterized in that additionally a crossbar, preferably the lower one, is movable in relation to the other crossbar, preferably the upper crossbar, for different inclinations and types of arc. 14. Formwork device according to at least one of the preceding claims characterized in that different clamping elements (4, 5) of the formwork sheet for the same formwork device are provided for different inclinations and / or types of arc. 15. Formwork device according to at least one of the preceding claims characterized in that with the formwork device arches of approximately 60 cm to 1.6 m can be made. 16. Formwork device according to at least one of the preceding claims characterized in that the strut (1) is a conventional steel support used in construction sites. 17. Formwork device according to at least one of the preceding claims characterized in that the formwork sheet (2, 2 ') is made in an elastic manner, but with its own rigidity sufficient to withstand the load of the concrete on site or of the masonry placed on the formwork sheet, preferably PVC, plastic, steel or wood. 18. Formwork device according to at least one of the preceding claims characterized in that the formwork sheet (2) is preferably fastened at the top point of the vertical strut (1) and at the free ends of the support arms, preferably by means of clamping elements (4, 5) of the formwork sheet, if necessary at the upper point of the strut (1) by means of a fixed connection between the formwork sheet (2) and the strut (1). 19. Formwork device according to at least one of the preceding claims characterized in that the joining elements of the parallelogram of each support arm (3) are support plates (8, 9), because the internal support plates (8 ) are fixed on the vertical strut (1), preferably by means of a flange (10) and a clamping element (11), because each upper cross member (7) is articulated together by means of a bolt (12) on the support plate inside (8) and by means of an axle (15) in the outer support plate (9), and each lower cross member (6) is articulated with a pivot (13) in a guide (14) in the support plate inside (8) and with a shaft (15) on the outer support plate (9). 20. Formwork device according to at least one of the preceding claims characterized in that the tensioning elements (21, 22) are coupled to the side ribs of the stirrups, and that the tensioning elements (22) of the clamping element (5) they consist of a clamping bar (23) and a rotating clamping screw (24) to move the clamping bar (23) in order to tighten or release the formwork sheet (2). 21. Formwork device according to at least one of the preceding claims characterized in that the tensioning elements (21, 22) are coupled in the lateral ribs of the stirrups (17, 18), and that the tensioning elements (21) of the element of tightening (4) are constituted by screws, which can be supported on counter supports (27), to tighten or release the formwork sheet (2) by means of adjustable levers (25). 22. Formwork device for the manufacture of arc-shaped limitations of openings in walls, with support devices (1, 4, 5) for an elastically deformable formwork sheet (2) comprising a vertical central strut (1) and two adjustable support arms (3) that protrude laterally on both sides of the strut (1) which, together with the strut (1), support the formwork sheet (2) elastically deformable, characterized in that each support arm (3) comprises an upper and lower crossbar (6, 7), where the crossbars (6, 7) of each support arm (3) are joined together at their outer ends, and their inner ends are orientably connected with the strut (1 ) at a top junction point and at a movable bottom junction point and form an open main parallelogram in which a smaller built-in guide parallelogram (F) is arranged in the orientable joint of the crossbars (6, 7), for always guide in its correct angular position with respect to the strut (1) a clamping element (5) for the formwork sheet (2), arranged at the free end of the support arm (3). 23. Formwork device according to claim 22, characterized in that the lower guide parallelogram (F) comprises the outer ends of the upper and lower crossbars (6, 7) and two auxiliary braces, each joined in an articulated manner with a crossbar , which have a common articulation point, and because an elongated support piece, approximately horizontal in relation to the vertical strut (1), is disposed on the adjustable joint of the upper and lower crossbars (6, 7), which has a linear guide for the point of articulation of the auxiliary braces and supports a vertical extensible tube (VS) with adjustable length that carries the clamping element (4). 24. Formwork device for the manufacture of arc-shaped limitations of wall openings, with support devices (1, 4, 5) for an elastically deformable formwork sheet (2) comprising a vertical central strut (1) and two adjustable support arms (3), protruding laterally on both sides of the vertical strut (1), which support the formwork sheet (2) together with the strut (1), characterized in that each support arm (3) It has a lower and upper crossbar (6, 7), where the lower and upper crossbars (6, 7) of each support arm (3) are fixed with their inner ends articulated and orientable on two movable supports on the strut (1), crossing at a point of articulation in the form of scissors, and which at their outer ends are orientably connected with an elongated support, approximately parallel to the strut (1), of a lateral clamping element (5) for the formwork sheet (2), where a groove guide (SL), approximately parallel to the strut (1), is provided on the support for a point of attachment between a crossbar and the support. 25. Formwork device for the manufacture of arc-shaped limitations of openings in walls, with support devices (1, 4, 5) for an elastically deformable formwork sheet (2) comprising a vertical central strut (1) and two support arms (3), which protrude symmetrically laterally on both sides of the strut (1) and support together with the strut (1) the formwork sheet (2), characterized in that each support arm (3) it has an extensible arm (SA) of adjustable length, which protrudes from an attachment in the strut (1) obliquely downwards and carries at the free end of the extensible arm a clamping element (5) for the sheet (2) of formwork and is supported by a crossbar (ST) approximately horizontal with respect to the vertical strut (1). 26. Formwork device for the manufacture of arc-shaped limitations of openings in walls, with support devices (1, 4, 5) for an elastically deformable formwork sheet (2), comprising a vertical central strut (1) and two support arms (3), protruding laterally on both sides of the strut (1) and supporting together with the vertical strut (1) the formwork sheet (2), and by an extensible horizontal arm (HS), or by two aligned horizontal arms (HS) aligned, guided in a displaceable way along the strut (1), where the extendable horizontal arm, or both extendable horizontal arms, with telescopically adjustable length, have clamping elements at their free ends ( 5) for the formwork sheet (2) and are supported by adjustable chains or adjustable straps (V) that run obliquely upwards and towards the strut (1), characterized in that the strut (1) has at least one groove guide (S) for extendable horizontal arm or arms (HS). 27. Formwork device according to claim 1 characterized in that in the strut (1) two curved cross members are arranged, which run symmetrically downwards and outwards, on which they are fixed in relation to the strut (1), or with the upper clamping element (4), the support arms (3) that hold the formwork sheet (2) in the arc shape and with the opening adjusted by means of the clamping elements (5). 28. Formwork device according to claim 27, characterized in that the two curved crossbars are fixed in an articulated way orientable in the strut (1), because, each curved cross member runs obliquely in the form of an arc from its point of articulation downwards and towards out to beyond the corresponding support arm (3), so that the concave side of the arc is directed towards the strut (1), because each curved cross member has holes in most of its longitudinal extension, arranged in a series of drills, whose intermediate distances increase with increasing distance from the point of articulation, and because around each curved cross member extends in the area of the free end of the support arm (3) a stirrup fixed in it in which it is arranged a body aligned with respect to the holes.