The invention relates a form for concrete and, in par¬ ticular, to a form for concrete wherein the surface of a form plate facing the concrete is covered with a po¬ rous web.

Forms for concrete are known wherein the form plates are respectively covered with a porous web. A porous web material suited for such purposes is marketed by DuPont De Nemours (Deutschland) GmbH under the trade¬ mark Zemdrain. The web material, pervious to water and air, effects a drainage of the water contained in the concrete, which may drain off through the web, and it prevents the forming of gas bubbles or blowholes at the concrete surface. Thus, a planar faultless con¬ crete surface of high quality and density is obtained that is of low susceptibleness to corrosion. The web material may have a structured surfa ^c e so that the concrete surface is provided with a defined roughness in order to form an adhesion surface for filling mate¬ rials or other surface coatings.

The porous web is fixed to the form plate by helical springs, one end of which is hooked to the web, while

the other end of the screw is fastened at a tensioning frame. Tensioning the web is a rather time consuming work, there being a risk of an unequal tensioning of the web and of folds or warps occurring in the web due to local stress concentrations.

Tensioning devices for stretching a textile web, e.g. for closing openings in buildings or for wall cover¬ ings _r are well known. US Patent 4,337,815 discloses a device for releasably holding a web. In this case, a holding profile is provided that has a recess into which two locking rods may be inserted. The end of the web is wound around the one locking rod, whereas the other locking rod serves as a blocking member. The holding device described in this patent principally allows a subsequent manual stretching of the web, but to this avail, the web has to be pulled by its end which requires considerable physical effort.

US Patent 3,928,897 describes a stretching device for stretchable wall fabrics. A profile frame is fastened to the wall, into which a profiled strip may be clam¬ ped. The end of the web is fixed at the profiled strip and the profiled strip is pivoted into the profile frame, thereby stretching the web. Both the profile frame and the profiled strip are located behind the web which, when mounted, is arranged at a distance from the wall. Such stretching systems are not suited for use with form plates.

US Patent 4,053,008 also describes a stretchable wall fabric with a tensioning frame to be attached to a wall, the stretched web being arranged at a distance from the wall.

It is the object of the present invention to provide a form for concrete that has an improved tensioning de¬ vice for a porous web, and, in particular, to provide a form for concrete wherein the tensioning device al¬ lows a fast and simple mounting and stretching of the web.

According to the invention, the object is solved by the features of claim 1.

In the tensioning device of the present invention, a profile member is provided that may be mounted in a fixed relationship to the form plate and has a rigid arm at which a first deviation member is provided. At the end of this arm, an outer first section of the web is fixed with a first clamping member. A second clamp¬ ing member having a second deviation member serves to stretch the web at the profile member in a defined manner. The clamping members are only pushed or pres¬ sed onto the profile member, or they are set thereon e.g. by hammer strokes. Because of the simple manner of mounting, the clamping parts are fixed in a very short time. It is also possible, to perform a subse¬ quent tensioning should heat, for example insolation, have caused an expansion of the web. The releasing or the removing of the form plate from the cured concrete can also be done in only a very short time since only the clamping members have to be removed. The web may either be taken from the concrete or be left thereon after the form plate has been removed.

The profile member, preferably made of steel, is ei¬ ther fastened to the form plate or to a support struc-

ture supporting the form plate. The invention may be implemented with any kind of form plate, be it of steel or wood.

Suitably, the clamping members consist of U-shaped integral structures each having a base member and two laterally resilient legs protruding therefrom. The first clamping member serves to fix the end of the web to the profile member, while the second clamping mem¬ ber forms a tensioning device for providing a defined tensioning of the web and additionally fixes the web. The fact that the second deviation member provided at the second clamping member lockingly engages the first deviation member provided at the profile member, pro¬ vides an additional locking safety effect, whereby the clamping members are prevented from coming off the profile member due to the tension of the web.

Preferably, the second clamping member is considerably larger than the first clamping member, but, generally, is of the same structure. The second clamping member straddles the first clamping member sitting on the end of the arm of the profile member.

Preferably, each of the two clamping members has an elongate base member from which pairs of legs protrude spaced from each other in the longitudinal direction. Thus, individual clamps are formed that are rigidly interconnected by the base member.

The following is a detailed description of embodiments of the invention with reference to the accompanying drawings.

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In the Figures

Figure 1 is a partly cut illustration of a first embo¬ diment of the form for concrete,

Figure 2 is a perspective view of the first clamping member,

Figure 3 is a perspective view of the second clamping member,

Figure 4 is a partly cut illustration of a second embodiment of the form for concrete,

Figure 5 is a partly cut illustration of a third embodiment of the form for concrete, and

Figure 6 is a partly cut illustration of a fourth embodiment of the form for concrete.

The form for concrete, as illustrated in Figure 1, comprises a form plate 10 which, in the present embo¬ diment, is solid and, as a whole, is made of wood. Instead of the throughgoing form plate 10, one may also use a profiled form plate having holes or reces¬ ses or openings, respectively. The form plate 10 is flat, however, it is also possible to use an arched form plate, e.g. a convex or a concave one.

The form plate 10 is supported by a form support 11 that may be fixedly connected to the form plate and which supports the back side of the form plate facing away from the concrete. Behind the form plate 10, a steel profile member 12 is fastened to the form sup-

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port. This profile member has a flange 13 attached to the wooden form support 11 by screws 14. Further, mounting plates 15 engage the flange 13 that are fixed at the form support 11 by screws 16 and which press the flange 13 laterally against the form support. A ridge 17 protrudes laterally from the flange 13, being bent downward by approximately 90°. The downward bent portion of the ridge 17 forms the arm 18 of the pro¬ file member 12 and extends rectangular to the form plate 10, the lower end 19 of the arm being directed away from the form plate. Between the bend 20 and the end 19 of the arm 18, there is provided the first de¬ viation member consisting of a shaped portion 21 form¬ ing a trough 22 on one side of the arm 18. The arm 18 of the profile member 12 consists of a web material having the same thickness all over.

The front side 23 of the form plate 10 facing the con¬ crete is covered with a porous web 24. This web 24 consists, for example, of a woven fabric or a nonwoven material. It is important that the web 24 is pervious to water and air and that it is of such tenacity that it may be stretched tightly. The web 24 may be single- or multilayered.

The outer first section 24a of the web 24 forms the end or the edge of the web. This section 24a is laid around the end 19 of the arm 18 and fixedly clamped to the end 19 by means of the first clamping member 25. First, the section 24a is laid onto the end 19 of the arm 18 from outside and, then, is bent around the end 19 by 180° so that the section 24a lies on both the outside and the inside of the end 19.

The first clamping member 25 has an elongate rod-shaped base member 26 and a pair of substantially parallel legs 27 and 28 protruding therefrom. These legs and the base member together form a U-shaped clamp, the width of which is slightly smaller than that of the end 19 with the section 24a of the web 24 lying there¬ on. The inner sides of the legs 27 and 28 are slightly diverging. When pushing the clamping member 25 onto the end 19 wound with the section 24a, the legs 27, 28 are spread apart. Due to the elasticity of the legs, the section 24a of the web is fixedly clamped to the end 19. In this way, the end of the web is fixed at the arm 18 of the profile member 12.

The second clamping member 30 is of a structure simi¬ lar to that of the first clamping member 25, but it is much larger. The clamping meber 30 has a longitudinal¬ ly extending rod-shaped base 31 and a pair of substan¬ tially parallel legs 32 and 33 protruding therefrom, their inner sides slightly diverging from the base 31 upward. Provided at the inner side of the leg 33, there is a second deviation member 34 that is shaped complementary to the first deviation member 21 of the arm 18 and, in the present embodiment, is a welded-on circular rod.

While the legs 27, 28 of the first clamping member 25 extend just up to the deviation member 23, at most, the legs 32, 33 of the second clamping member 30 are long enough to extend beyond the first deviation mem¬ ber 21. While the leg 32 is supported on the outer side of the deviation member 21, the deviation member 34 at the other leg 33 engages into the trough 22. In doing so, the deviation member 34 forces the inner

the deviation member 21. Thereby, the web 24, the outer section 24a of which is fixed at the end 19 of the profile member 12, is tensioned, because the inner section 24b of the web is deviated between the devi¬ ation members 21 and 34 and a certain length of the web is used up in this deviation. The second clamping member 30 is secured against co ing off the profile member 12 by the interlocking deviation members 21 and 34.

Figure 2 illustrates a perspective representation of the first clamping member 25. The base 26 is an elon¬ gate rod of spring steel of about 10 to 200 cm in length. Two pairs of legs 27, 28 are respectively ar¬ ranged thereon at distance between 10 and 50 cm so that the pairs of legs are spaced apart in the lon¬ gitudinal direction of the base 26. The legs 27 and 28 have diverging inner sides 35 flaring at their ends.

Figure 3 shows a perspective view of the second clamp¬ ing member 30. Again, the base 31 is an elongate rod of spring steel with a length of 10 to 200 cm. From the base 31, pairs of legs 32, 33 project that are spaced apart in the longitudinal direction of the base. The inner sides of the legs 33 press against a flattened portion of the second deviation member 34 which extends parallel to the base 31 and has sub¬ stantially the same length as the base. The distances between the pairs of legs measure between 10 and 50 cm.

In the present embodiment, the first and second clamp¬ ing members 25 and 30 are straight, i.e. each has a straight base and the second clamping member 30 has a

straight deviation member 34. It is also possible to provide arched clamping members so as to achieve an adaptation to a concave or convex edge of a form plate. To achieve such adaptation to curved form plates, one may also arrange a plurality of successive short straight clamping members in the shape of a draft of traverse. Due to the fact that the arm 18 of the profile member and the second deviation member connecting the legs 33 of the second clamping member 30 are continuous in longitudinal direction, a uniform clamping and a warp-free tensioning of the edge of the web 24 is obtained.

On the other hand, it is also possible for one clamp¬ ing member 25 or 30 to have only a single pair of legs, a plurality of such short clamping members being set on the profile member in this case.

In the embodiments of Figures 4 to 6, the same clamp¬ ing members 25 and 30 are used as in the first embodi¬ ment. The respective differences only relate to the type of the form plate and the profile member.

While, in the first embodiment, the arm 18 of the pro¬ file member 12 extends rectangular to the form plate 10, the arm 18, as depicted in Figure 4, extends up¬ ward from the end of the form plate support 11, when the form plate 10 is vertically orientated, and in parallel to the form plate 10. Thus, the web 24 is not drawn under the form plate around the edge of the form plate 10, but, in extension of the form plate 10, it is drawn outward with only a little deflection.

In the embodiment of Figure 5, the form plate support 11 is made of steel. In this case, the profile member

12b is welded or screwed to the back side of the steel form plate support 11a facing away from the form plate 10, the arm 18 extending rectangular to the form plate 10.

In the embodiment of Figure 6, with a vertical form plate 10, the form plate support 11a is made of steel. Here, the profile member 12c is welded or screwed to the front end of the form plate support 11a so that the arm 18 projects laterally from the form plate sup¬ port 11a and extends parallel to the form plate 10.