STIFFENING OF PLASTIC FORMWORK ELEMENTS

Abstract: Stiffening of plastic formwork elements composed of plastic formwork blocks is carried out so that settlements and formations of cracks including related distortion are avoided when introducing I-profiles extending between the opposed walls of the formwork element, and which flanges by pressure, gluing or in another way are attached to these walls. The web of the I-profiles is provided with macroscopic openings of a such dimension that the floating concrete may freely flow unobstructed therethrough.

Description: Stiffening of plastic formwork elements The present invention relates to a method of stiffening formwork blocks which for example may consist of styropore (expanded polystyrene) and foundation wall elements composing a number of such interconnected blocks, connected with stiffening elements. A quick and simple method for casting isolated walls is to construct such walls by hollow blocks, consisting of vertical-standing side walls connected by webs and which are open in the upward and downward direction, normally by interconnecting devices of a "male/female" system at the top and the bottom of the walls. When a wall is built up by the formwork blocks, concrete is poured from the top and fills the cavity (space) inside the blocks and cures to a compact wall inside the element which gives the walls an intended mechanical strenght, while the outside plastic walls simultaneously provide isolation. Such blocks are for example described in Norwegian patent publication No. 160,799. A problem in constructing such walls is that during filling of the liquid concrete material, the blocks have a tendency to be forced up - often locally - due to the weight of the concrete mass. This may result in minor cracks with a size in the order of mm in the wall, and hence misalignment (distortion) in the wall. To solve this problem, an outside stiffening of the construction block wall has been provided during pouring of the liquid concrete. This stiffening which often is wooden columns (posts) or frames, thereafter are removed. This involves extra work at the construction site. Further, it is often desirable to provide a such wall with nailing strips. Therefore, a subject of the present invention has been to provide a permanent stiffening of the formwork elements composing interconnected light-weight plastic blocks of heights which normally will go up to 2,5 m, but which also possibly could be built higher. Further, it will in many cases, as mentioned earlier, be desired to provide fixed nailing strips on the concrete side of the plastic material walls. Therefore, the present invention relates to a method of stiffening plastic forwork elements consisting of interconnected plastic material forwork blocks, characterized by that in the space between opposed walls of the formwork element, is introduced stiffening elements with an I-profile, wherein the flanges are forced and eventually glued against the opposed walls of the formwork element, eventually introduced into preshaped grooves in these, and the web of the I-shaped stiffening profile is provided with macroscopic openings. The flanges on the stiffening elements may be glued to the plastic material walls with expanded glue (adhesive) to provide an optimal connection. The stiffening elements are installed in the wall so as to be in a vertical position when the wall is upright, and they may, if desirable, be placed between each web in the plastic blocks or with a lower frequency if desirable. It is often suitable to design the flanges of pressure treated wood to provide nailing strips as mentioned earlier, but also other materials such as metal profiles, which do not allow this possibility, could be utilized. The web itself could with advantage be a truss (grid) girder such as a reinforcement beam SB consisting of two parallell extending metal threads with desired spaced apart distance connected with diagonal extending thread (in zig¬ zag) , in which different ways of connecting such as spot welding etc. the stiffening thread to the parallell threads may be utilized. The truss girder may in different ways be connected to the flanges when these are made of wood, for example by cramps or the like, and may also be installed in a preformed groove in the flanges. However, the web may have other configurations, which for example could be a metal plate with sufficient large holes so that the concrete during filling will floate unobstructed therethrough. However, this is specially favourable achieved with said truss girder, where the concrete will float with the smallest possible resistance, and whereby a reinforcement simultaneously is embedded in the completed wall. The present invention also relates to such formwork elements consisting of interconnected formwork blocks to the desired dimension in height and length, which are characterized by that their stiffening elements consist of vertical standing I-profiles with macroscopic openings in the webs where the flanges rest against, and preferably are connected to, the opposed walls. Construction elements of this kind will be made completely stiff in the same way as a laminated construction and will not suffer from the previous problems concerning formation of cracks and torsion which lead to misalignments (destortions) and irregularities in the walls during casting. If desirable, a stiffening in the length direction of the wall may be provided by placing a corresponding stiffening device or only the flange there of horizontally in the bottom and the top of the wall, and connect these respectively to the bottom and the top of the flanges. By doing this, one will also achieve an increased stiffening in the length direction of the walls. Elements of the type described have the great advantage that they may be manufactured both at the construction site and prefabricated in a fabric as large completed, stiffened elements (forwork walls) with the desired dimension, ready for mounting and filling in of liquid concrete. Simultaneously they are easy to handle so that they do not require their own lifting equipment at the construction site. A manufacture of such elements may be carried out by continuous manufacturing, as for example expanded polystyrene elements or the like are succesively mounted together, introducing the stiffening elements, pushing the product forward, extending it by making up new formwork blocks, installing the stiffening elements, pushing forward, etc. The wall may be located in both a vertical and horizontal position when the stiffening elements are installed. By continuous production the elements may be cut in desired lengths, for example as standard lengths of 0.6, 1.2, 2.4, 3.6 m etc., or the lengths are cut according to order. Parts of the web may eventually be sealed (closed) at places where for example openings for windows are desired, so that the concrete will not fill this space. The design of the webs may be varied according to the desired nailing strips. The formwork element according to the invention is illustrated with reference to the attached drawing. The figure illustrates a part of a stiffened formwork wall (1) built up by formwork blocks (2) . The blocks have parallell extending opposed walls (3) connected by web (4) . In the opposed parallell extending walls (3) a groove (recess) (6) is provided. In the formwork blocks it is introduced a stiffening element with an I-profile where the flanges (5) are guided in the grooves (6) . The web (8) which connects the flanges consist of a truss girder The diagonal extending thread in the truss girder will normally have a dimension of 4-7 mm, when the parallell extending threads which are connected to the flanges, normally will have a diameter of 5-12 mm. The stiffening elements in the figure are introduced with a such distance that they have two webs of the formwork blocks in between. The invention is not intended to be restricted to the illustrated figure, which only constitutes an example of one of a number of possible embodiments of the invention, since the field of invention is restricted of the attached claims.

Claims: PATENT CLAIMS 1. Method of interconnecting stiffening of plastic formwork elements (1) including integrated webs, consisting of composed plastic material formwork blocks (2) , c h a r a c t e r i z e d b y that in the space between the opposed walls (3) of the formwork elements (1) is inserted stiffening elements (7) with a length about equal the height of the formwork element (l) and with an I-profile the flanges (5) being closely inserted against and glued or attached in another way to the opposed walls (3) of the formwork elements (1) , eventually introduced into preshaped grooves (6) in the walls (3) and glued or attached in another way to these, as the web (8) of the stiffening elements (7) being provided with large openings which freely allows the concrete to flow there¬ through. 2. Method as claimed in claim 1, c h a r a c t e r i z e d b y that the web (8) of the stiffening element (7) is glued to the walls (3) of the formwork blocks (2) with expanding glue (adhesive) . 3. Formwork element (1) composed of plastic material formwork blocks including integrated webs, c h a r a c t e r i z e d b y the stiffening elements (7) including vertical standing I-profiles with length equal to the height of the formwork element (1) and with large openings in the webs (8) which allow free flow of concrete there¬ through, which flanges (5) rest against, or in formed recesses (6) in, and preferably are attached to, the opposed walls (3) .

Inventors: LOHNE THORBJOERN, LOHNE, THORBJOERN
Applicants: LOHNE THORBJOERN, LOHNE, THORBJOERN
Application year: 1992
Main classification: E04B2
IPC codes: E04B2