Building block comprising light transmitting fibres and a method for producing the same

0001The present invention relates to a building object made of a cast material with a partial light transparency, comprising light transmitting fibres embedded in the cast material. The present invention also relates to a method for producing the building object comprising embedded light transmitting fibres.

0002For practical and decorative reasons it is usually frequent that a building object, such as a wall-, floor-or ceiling-surface is illuminated by one or several separate sources of light, e. g. so called spotlights, directed to the surface in question. Nowadays it is also popular to mount lamps in building elements, such that they are recessed and/or flush with the surface, which provide some lighting over the surface and some lighting in adjoining rooms adjacent to the surface.

0003A first group of building objects relates to building elements or blocks with a predetermined mechanical stability required for being used in building constructions.

0004<patcit id="pcit0001" dnum="FR2745135"><text>FR 2745135</text></patcit> belongs to this first group and it discloses an illumination/lighting apparatus, which comprises the combined use of concrete or cement, and systems based on optical fibres fed with light. The optical fibres are enclosed in a protective sheath and the fibres are organize in bundles. One end of the bundles of the optical fibres is provided at a wall surface and embedded in concrete, while the other ends of the bundles of the fibres end up at a light source such as a lamp.

0005A second publication of this first group is <patcit id="pcit0002" dnum="GB1561142A"><text>GB 1561142</text></patcit> from which it is previously known to arrange light guiding bars comprising bundles of optical fibres, in drilled through holes between two opposite sides of a building element. Light from a light source that illuminates a rear side of the element is guided through the bars bundles of fibres to the opposite side.

0006A second group of semi-transparent building objects include German utility model <patcit id="pcit0003" dnum="DEG9310500"><text>DE G 9310500.2</text></patcit> that describes a disc-like thin building object that uses optical light conducting cables embedded in the cast material from which the object is made, wherein the cables are evenly spread and provide a limited light transparency. In an embodiment one of the surfaces of the disc-like object comprises a further light transparent element that serves optical tasks i.e. colouring or spreading the transmitted light. The publication is silent concerning the position and arrangement of the light transmitting cables and how such cables can be embedded in the cast material to keep their positions and not to be displaced during the casting step under the weight of the paste-like cast material. For attaining a noticeable transparence a large number of light conducting cables should be placed, which placement and positioning will become very problematic and expensive, especially when the object is thin.

0007The optical properties of the semi-transparent building object are largely defined by the way how the fibres are arranged within the object. One known cable arrangement is described in the cited <patcit id="pcit0004" dnum="FR2745135"><text>FR 2745135</text></patcit> wherein the light transparent cables are spread out at one surface and focused to the light source at their other ends, whereby they have a conical positioning within the concrete body to divert the light of the light source.

0008In the first group of the cited building object it is unpractical, time consuming and costly, as mentioned above, to mount light sources or optical cables in prepared building elements or in built walls, ceilings or floors, in order to transfer light through the building element. Particularly, if discrete small light sources should be mounted in the building element. If a considerable part of a surface shall emit light, it is easily appreciated that the work will be lengthy since a large number of holes have to be made. Besides, only amounting of a limited number of light sources in the building element can be done by these known methods, if not influencing the strength of the element.

0009In case a light emitting and/or illuminating effect is desired to be provided combined with sufficient strength, the way how the light conducting fibres are arranged and embedded in the cast material will be significant, since the structure determines both the optical and mechanical properties. Uniformity is a further requirement, as different objects must have largely identical optical and mechanical properties. In this regard the cited second group of building objects has failed to describe any structure and ways for providing uniformity.

0010The object of the invention is to provide a semi-transparent building object made of a cast material that can be used as a building block and has the required mechanical strength, and wherein the light conducting elements are embedded and arranged in the cast material of the object in such a way to ensure the needed uniform optical and mechanical properties for different objects. A further object lies in providing a method for making such building objects.

0011These objects have been achieved by providing a building object and method for making the same as defined in the attached claims.

0012In the present building object the cast material and the embedded fibres therein constitute a building block with a homogeneous layered structure of the embedded fibres extending parallel with each other between a rear and a front surface of the block.

0013An advantage with this solution according to the invention is that a pre-fabricated light transmitting building block is provided. By means of the fibre ends that ends up at the lateral surface according to the invention it is thus possible to achieve light sources at certain spots evenly spread over substantially the whole lateral surface, which provides a feeling that the whole lateral surface is illuminated, alternatively is emitting light. Yet an advantage is that the light transmitting fibres are wholly integrated with the cast material presenting thereby a homogeneous structure with the capability to receive large loads.

0014The cast material can be of concrete, cement, gypsum, plastics, metal or the like. Suitably use is made of concrete or cement that provides an average density of the prepared building block within the range from about 2200 kg/m³ up to about 2400 kg/m³. The number of fibres per building block can be in the range from some hundred up to some thousand. The volume relation of the cast material and fibres is preferably within the range from about 1: 15 up to about 1: 8. A suitably dimension of a building block produced by the method according to the present invention is e. g. 250mm/120mm/68mm, which has a weight of about 5 kg and a concrete/fibre relation of 1: 13.

0015The present invention will now be described more in detail by way of examples, with reference to the accompanying drawings. In the drawing: <ul id="ul0001" list-style="none" compact="compact"><li><figref idref="f0001">Fig. 1</figref> shows in a perspective view at an angle from above of a building' block according to the invention;</li><li><figref idref="f0001">Fig. 1B</figref> shows a cross-section A-A of the building block in <figref idref="f0001">Fig. 1A</figref>;</li><li><figref idref="f0001">Fig. 1C</figref> shows a longitudinal section B-B of the building block in <figref idref="f0001">Fig. 1A</figref>;</li><li><figref idref="f0001">Fig. 1D</figref> shows a partially perspective view of a wall built of a number of building blocks according to <figref idref="f0001">Fig. 1A</figref>; and</li><li><figref idref="f0002">Figs. 2A-C</figref> show in schematic illustration various steps of a production method of a building block according to the present invention.</li></ul>

0016A building block 2 according to the invention is shown in <figref idref="f0001">figs. 1A-C</figref>. The building block comprises a cast material 4 and embedded light transmitting fibres 6 in the cast material. The fibres are arranged in the cast material from a first lateral surface 8 of the building block to an opposite second lateral surface 10. One end of a fibre 6, respectively, is arranged to end up at a position 12 at the first lateral surface 8 and the other end of the fibre is arranged to end up at a position 14 on the second lateral surface 10. Pluralities of fibres 6, suitably some hundred single fibres, are arranged in parallel in the longitudinal direction L of the building block. The fibres are evenly spread in the block 2 and the ends of the fibres thus ends up at the lateral surfaces in positions 12, 14 over substantially the whole lateral surface 8, 10, respectively. The fibres permits that light is transferred through the building block emitted from a light source arranged e. g. behind the second lateral surface 10, to the first lateral surface 8, or vice versa, whereby light is emitted from the evenly distributed fibre ends in positions over substantially the whole lateral surface.

0017In that fibres are evenly distributed in the block 2 and that the cast material substantially surrounds respective fibre as evident in <figref idref="f0001">figs. 1A-C</figref>, the block forms a homogeneous structure with high strength. Load-bearing walls of desired size and extension could thereby easily be constructed with a number of integral building blocks 2 as is evident from <figref idref="f0001">fig. 1D</figref>.

0018In <figref idref="f0002">figs. 2A-C</figref> is shown a production method according to the present invention, for production of a building block 2 according to the invention as described above. In an elongated mould 20 (see <figref idref="f0002">fig. 2A</figref>) of e. g. steel or wood, is in a first step a cast material 4 added.

0019In a second step is a layer 22 of fibres 6 arranged in the longitudinal direction of the mould 20. In a third step, the mould is subjected to a mechanical pressure and/or vibration such that the fibre layer is permitted to sink into the cast material to a desired depth. Then, steps one to three is repeated, alternatively steps two to three, until the mould is filled with the cast material and several fibre layers. Each layer 22 constitutes of a plurality of parallel fibres 6, for example some twenty fibres or more per layer. The thickness of the layer and the fibres may suitably be about 1 mm and the number of layers can be some twenty or more. The fibre layers 22 are fed continuously in the mould 20 from a fibre roll 24 via a nozzle 26 that provides for an even distribution of the fibres along the whole, transverse direction T of the mould. When the cast material 4 has become solidified, the solid moulded body 28 is divided by cutting into separate building blocks 2, e. g. with the dimension 250mm/120mm/68mm. The cutting is done such that the ends of the fibre layers 22, respectively, end up at a lateral surface 8, 10, respectively, of the building block 2.