PROCEDURE FOR CASTING OF BUILDING ELEMENT; THE LT-METHOD

Abstract: The present invention relates to a method of manufacturing prefabricated walls or floor structures. Preferably, single-course cast walls and thin-plate floor structures with insulation moulded therein. To avoid uneven compression of the insulation, the casting concrete is poured into a sloping form or an upstanding form which is brought to a horizontal position after having been filled with concrete. The walls can be made completely free of thermal bridges caused by concrete encroaching in the insulation.

Description: PROCEDURE FOR CASTING OF BUILDING ELEMENT; THE LT-METHOD The present invention relates to a method pertaining to the casting of prefabricated building units such as walls, building blocks, foundation beams and floor structures, preferably single- course plates to which or in which insulation is fastened or moulded. BACKGROUND OF THE INVENTION Present-day technology relating to the construction of cellars, split-level houses and multi-storey buildings, and also single- unit dwellings and multi-unit dwellings having concrete walls and concrete floor structures, utilises insulated concrete wall units together with di fferent types of prefabricated floor constructions. PROBLEMS ENCOUNTERED IN MANUFACTURE Problems encountered in the fabrication of wall units that incorporate thermal insulation. Patent specification SE 501752 teaches a method of pressing sheets of insulation down into the concrete of the wall plate under vibration. The casting concrete has earlier been poured into the mould. Drawbacks: This method requires the volume of concrete to be determined very accurately, in order for all cavities, slots, etc., in the plate to be filled. Precision weighing devices are used in practice, where each building element or fabricated unit shall contain a precise amount of concrete. Windows, doors and also other minor cut-outs must bp taken into account. The purpose of the thermal insulation is to thermally insulate the building and to function as a plaster carrier. It has been found that insulation cannot be made too dense from a thermal insulation aspect. It is, after all, the porosity and gas enclosures that provide a thermal insulating effect. A slightly flexible and therewith resilient insulation will yield as it is pressed into the concrete, which must be done whilst exerting heavy pressure against the concrete. The insulation does not have precisel uniform resilient properties and the concrete is not always able to flow out and fill all cavities. This results in walls of uneven thickness. We obtain a smooth surface inside of the building, since the concrete plate is turned inwards, whereas the insulation on the exterior of the building is stepped between the unit parts. These steps may be as much as one centimetre in size. This requires a very thick layer of finishing cement or plaster to be applied in order to obtain a smooth outer surface, therefore greatly adding to costs. This method of producing prefabricated wall elements or units is also encumbered wi l t the drawback of requiring the application of very heavy forces in pressing down the wall insulation, which has a very wide surface area. The method according to our invention enables units of optional lengths and having a width of 2.4 m to be fabricated with no difficulty. It is also conventionally possible to cast a concrete plate on top of the thermal insulation, although this requires a piece of solid workmanship in treating the surface of the concrete plate so that it becomes straight, smooth and free from pores. Other known techniques: Upstanding forms are also used for wall fabrication, sometimes in mutually adjacent relationship, so-called battery forms. The height of the wall units must correspond to the height of a storey plus the height of a floor structure. During casting, this height produces a vibrating concrete column (cf. liquid column) that has an enormous explosive effect and generates horizontal forces that greatly exceed a purely stationary "concrete liquid". The insulation is subjected to still greater compression than when the insulation is pressed into a horizontal concrete mass, and still greater variations in thickness occur. The floor to ceiling heights of present-day residential building developments exceed 2.4 m. heights of 2.6 to 2.7 m are not unusual. In the case of battery-mould casting, the explosive effect is worse than the above-mentioned. The present invention also provides a solution to the aforesaid problem. OBJECT OF THE PRESENT INVENTION With respect to moulding-in wall insulation, the object of the present invention is to improve the tolerances on primarily the thickness of a prefabricated wall unit with moulded-in insulation. This without needing subsequently work the unit with expensive facing cutters. Face cutting processes waste material and generate a noisy and dusty environment. Solutions of the problems with insulation that is compressed during casting of a prefabricated wall unit and means for fastening the concrete of the wall plate to the insulation: Incorporation of the insulation in the wall concrete plate: Because the wall units of this invention do not have any T-web reinforcements, i.e. any deep channels in the thermal insulation that can weaken it as it is handled prior to casting, sheets that have widths up to the width of the wall unit can be used. Suitable types of insulation are sheets of cellular plastic. The insulation is provided with grooves that are filled with concrete as the units or elements are cast. These grooves can be given the form of vertical, horizontal or inclined channels as seen in relation to an upstanding, mounted wall unit. The channel bottoms are made 1 arger inwardly of the insulation as seen from the surface, e.g. have a dovetail shaped cross-section. A suitable tool is a conical cutter with the base at its end. The channels, or grooves, may have a depth of from 1 to 2 cm, for instance. These channels will not weaken the sheet of insulation to any appreciable extent, considering that these sheets will normally have a thickness of at least 200 mm. This casting method is intended for use in constructions described in the original application, with toothed or finger-like attachment between floor structure and wall plates. This supporting method results in purely centrally vertical loading in the wall plates and eliminates the need of reinforced T-beam webs. Consequently, in manufacture, the casting concrete need not rise to a particularly high level when the concrete plate lies undermost, e.g. against a steel mould, as compared to the height it is required to rise in the case of reinforced T-beam webs, which are normally a decimetre in height. DESCRIPTION OF CASTING PROCEDURE According to the present invention, casting is carried out in accordance with the following method. Any forms required for window cavities and other cavities in the wall concrete plate are applied conventionally. Wall reinforcement is placed in the mould. Prior to casting, the prepared insulation sheets are fixed at the correct unit thickness with spacing blocks against the mould for the concrete. Or are lifted from the mould and held in place with the aid of suction cups through the medium of a vacuum, without requiring the use of blocks. There is always a risk of blocks being torn away by the heavy concrete mass; see below. Suitable stop means prevent the insulation sheets moving from the mould as the concrete is poured thereinto. SOLUTION Pouring concrete into a sloping mould. One end of the moul i .<- lifted so that the mould bottom builds an inclined plane or surface. The fastener channels in the insulation to be filled with concrete are suitably orientated in the longitudinal direction of the slope so that no unnecessary air pockets will form. The concrete is poured in from the upper edge of the slope, optionally while vibrating. The upper edge can be formed by any side of the unit whatsoever. When casting extremely tall units, e.g. two-storey units, the concrete is poured from the long side of the unit. After having filled th mould with concrete, the mould is lowered to a horizontal position back on its foundation or pallet attachment, w ioh provides stability and straightness in a conventional manner. Pressure against the insulation also ceases therewith. Light vibration can be employed to ensure that the concrete will flow out towards the steel mould. In this stage of the process, supplementary concrete can be supplied in the case of complicated forms, e.g. around windows apertures in which windows shall be fitted slightly out towards the outside of the wall and when wishing to provide in the aperture internal concrete linings that do not need subsequent treatment. Rising vents that allow air to escape in the concrete pouring operation can be readily provided at such locations, by providing holes in the insulation. With modern-day casting techniques and effective methods of enhancing the flow of concrete during casting, concrete may also be injected centrally through such holes or openings provided in the insulation. The mould may very well lie horizontally in this case. A check is made in the rising vents that all cavities to be filled with concrete have actually been filled. In a reverse procedure with the grooved insulation forming an inclined mould bottom in accordance with the above, and an overlying mould, e.g. a steel mould, that is held spaced from the mould bottom to form a gap for receiving the supporting plate. Plate reinforcement is spaced from the insulation sheet and holds the sheet m placo, so that the sheet will not float up. This casting method enables the insulation sheets to be made in large units, and also enables holding means to be provided against the overlying mould, to avoid the insulation floating up. The concrete/casting compound poured in the upper edge of the gap in accordance with the aforegoing runs readily down into fastener channels and pockets for windows, etc., wherewith the air is pressed up towards the overlying planar mould and has a much broader way out, which facilitates filling-out the mould with casting compound. As the gap is filled with casting compound, vibrators placed on the upper mould result in requisite packing of the relatively thin concrete plate right down to the insulation sheet. Vibrators placed along the sloping mould can be switched on and off respectively as the gap is filled. This will depend on whether or not vibration is required; see below. Because the mould is inclined whilst being filled, the "liquid height" is reduced and therewith the pressure on the insulation. This will not be compressed to the same extent as if the mould was upright or as in the case when the insulation is pressed down into the concrete mass. When the mould is returned to a horizontal position, the load acting on the insulation is removed completely. And the object achieved => a unit of uniform thickness. Also straight with a concrete surface that is cast against a steel mould: Ready to paint. It should be pointed out that particularly plastic concrete compositions which need not be vibrated during a casting operation are now commercially available. It will be seen that this gives typical interest to the aforedescribed casting procedure. The invention is defined in the accompanying independent Claim. Further developments of the invention are set forth in the dependent Claims. Only walls that incorporate insulation have been included in the examples, although it will be understood that the invention can be applied with respect to foundation beams having thin, preferably vertical sheets. Or roof plates in which insulation is firmly embedded. It will also be understood that the present invention is not restricted to the aforedescribed exemplifying embodiments thereof and that the invention includes all of the embodiments and similar solutions that lie within the scope of the following Claims.

Claims: CLAIMS 1. A method of fabricating a thermally insulated unit which includes a supporting layer of cast material and a layer of thermally insulating material which is fastened against and orientated generally parallel with the cast layer, c h a r a c t e r i s e d b y providing an openable mould that has a mould cavity whose shape corresponds to the shape of said unit; in that the layer of thermally insulating material is introduced into the mould and held firmly against and generally parallel with a main surface of the mould cavity; in that the mould is positioned to define an angle between said main surface and the horizontal plane; and in that the casting material is introduced into the mould via a high point in the mould cavity whilst keeping the mould at an angle relative to the horizontal plane. 2. A method according to Claim 1, c h a r a c t e r i s e d b y lowering the mould after filling said mould and prior to the casting material having hardened, so as to cause the cast sheet to lie generally horizontally during the hardening or curing process. 3. A method according to Claim 1 or 2, c h a r a c t e r i s e d i n that the thermally insulating layer has undercut recesses in its main surface facing the casting material. 4. A method according to Claim 3, c h a r a c t e r i s e d i n that that the recesses have the form of elongated grooves having an undercut cross-sectional shape; and in that the mould is orientated so that the grooves will extend in a direction that deviates from the hori zontal during the casting process . 5. A method according to Claim 3, c h a r a c t e r i s e d i n that that the mould is orientated so that the grooves lie generally in vertical planes that are perpendicular to the plane of the layers. 6. A method according to any one of Claims 1-5, c h a r a c t e r i s e d i n that the unit is a prefabricated building unit; and in that the casting material is concrete. 7. A method according to any one of Claims 1-6, c h a r a c t e r i s e d i n that the insulating sheet is formed by edge- joining sheets of insulating material. 8. A method according to any one of Claims 1-7, c h a r a c t e r i s e d i n that the sheet of thermally insulating material extends over at least a part of the main surface area of said unit.

Inventors: WEGLER GEORGE, WEGLER, GEORGE
Applicants: WEGLER GEORGE, WEGLER, GEORGE
Application year: 1998
Main classification: B28B23
IPC codes: B28B19, E04B1, E04B5, E04C2