Patent Publication Number: US-2002011549-A1

Title: Encasing skins using transparent material for fair-faced concrete

Description:
BACKGROUND OF THE INVENTION  
       [0001] The invention concerns an encasing component for fair-faced concrete with a supporting frame and an encasing skin stayed by the latter.  
       [0002] For some decades fair-faced concrete has become popular in architecture, which makes plastering or painting unnecessary but, for aesthetic reasons, should have a flawless surface. For encasing fair-faced concrete walls, wooden support encasings and steel frame encasings of relatively large dimensions are used for instance, these being constructed so that they withstand the pressure of the concrete when it is poured. The surface facing the concrete, the encasing skin, consists of smooth wooden or steel plates with the surface quality that is necessary for the evenness of the fair-faced concrete. The encasing sections for a wall are fixed in place by threaded rods, which—surrounded by a pipe—penetrate the wall and project on both sides through the encasing sections so that they can be fixed by nuts. In actual practice, so-called concrete nests easily appear at the surface on these joining points, caused by inadequate compression in the region of the exit of the threaded rod. These concrete nests are visible in the concrete surface after removing the encasing and detract from the appearance of the fair-faced concrete. Frequently the entire wall then has to be torn down and poured anew, meaning considerable effort and cost.  
       SUMMARY OF THE INVENTION  
       [0003] The object of the invention is to create an encasing for fair-faced concrete that enables these disturbing concrete nests to be avoided and fair-faced concrete surfaces to be produced that are free of flaws.  
       [0004] This object is solved by the features stated in claim  1 . Further embodiments of the invention are defined in the subclaims.  
       [0005] The invention is based on the experience that unwished concrete nests, air gaps and other flaws in the fair-faced concrete, which can appear despite the use of vibrators, are not noticed until the encasing is removed, i.e. when the concrete has already settled and no corrective compression is possible any longer. If one had sufficient means of checking the compression at critical points while pouring, better compression could be produced with the vibrator at the points concerned, or the turnscrews for the encasing could be retightened to produce the correct compression.  
       [0006] The invention creates the possibility of such a check through the amazingly idea of using transparent material for the encasing skin instead of the wooden or steel plates customary to date, so that the fair-faced concrete can be watched through the encasing skin while pouring and the still fluid concrete can be compressed extra, if necessary, at points where irregularities of the fair-faced concrete begin to emerge before the concrete settles. The transparent material of the encasing skin should be fracture-proof, impact-resistant and scratch-resistant so that it is not damaged during rough building site operations. Glass clear plastic material like Makrolon, for example, has shown itself to be especially suitable, satisfying the requirements for the purposes of the invention and whose cost is negligible compared to the effort of tearing down and repouring a fair-faced concrete wall with surface flaws.  
       [0007] Within the framework of the invention it is also possible to create visible grooves in the concrete surface by providing strips on the transparent encasing skin for example, preferably of the same material, by adhering them or possibly forming them as one part with the encasing skin. In this way, in the region of such visible grooves, which can be provided for optical subdivision of large fair-faced concrete surfaces, impairments of the concrete surface can be recognized in good time and made to disappear. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0008]FIG. 1 is a perspective view of a wooden support encasing with the encasing skin according to the present invention; and  
     [0009]FIG. 2 is a perspective view of one embodiment of the encasing skin according to the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
     [0010] The invention will now be explained in more detail with reference to an example of its implementation illustrated in the accompanying drawing. It shows the single figure of a wooden support encasing with the encasing skin according to the invention.  
     [0011] A frame  2  standing on the ground serves to hold a wooden supporting structure  4  upright as part of a wall encasing. Attached to the wooden supporting structure is an encasing skin  6 , which, as in the invention, consists of glass clear plastic material, preferably a polycarbonate plastic, and which determines the fair-faced concrete surface with its surface facing away from the wooden supporting structure  4 . Suitable materials for the encasing skin  6  are plastic materials that allow a transparent view on the concrete behind the skin, such as PVC-based plastic materials, polycarbonate-based plastic materials and polymethacrylates. The thickness of the encasing skin  6  is preferably between 5 to 30 mm, more preferably 10 to 20 mm, e.g., 12 mm. Through a combination of several such elements as shown in the figure, fair-faced concrete surfaces of any size can be produced. The encasing can also be formed in the same size as the fair-faced concrete surface that is to be produced of course, i.e. as long as it is still easy to handle.  
     [0012]FIG. 2 illustrates the provision of structures  8  on the transparent encasing skin  6  according to the invention, which is shown without the supporting structure. The structures  8  are adapted to create the above visible grooves or alternatively visible projections on the concrete surface. The shape and dimension of the structures  8  are selected in dependence on the intended aesthetic appearance of the concrete wall.  
     [0013] The invention is by no means restricted to wooden supporting encasings of the kind illustrated. The transparent encasing skin can also be used on other supporting structures, for example steel frames, which is not separately illustrated however. What is decisive is that the encasing skin, non-transparent to date, becomes transparent by the invention and allows observation of the fair-faced concrete surface while pouring fair-faced concrete walls for timely elimination of visible flaws.  
     [0014] The encasing skin of the invention can be formed as an integral skin or alternatively, as a multilayer structure consisting of a plurality of thin bendable transparent plates. As an example, three thin transparent plastic plates can be combined for forming the encasing skin wherein each of the plates have a thickness of 5 mm. The thin plates have essentially the same shape. They are connected to each other with clamps along the outer circumferences thereof. The advantage of this embodiment of the invention is realized if non-planar concrete walls are to be poured. The thinner plates allow an adaptation of the encasing skin to the shape to be poured due to their elasticity.