Measuring and testing – Miscellaneous
Patent
1997-04-24
1998-12-29
Raevis, Robert
Measuring and testing
Miscellaneous
B29C 3100
Patent
active
058544267
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND
The invention relates to a method for metering and distributing pouring material comprising a mixture of wood fibers or such base materials and a mineral binding agent for the production of chipboards, fiber boards or particle boards, especially cement-bonded particle boards, wherein the pouring material is metered volumetrically and the volume and/or weight of the supplied pouring material is controlled.
In the production of mineral-bonded particle boards fiber boards, stringent demands are made in metering and distributing the pouring material. To obtain high quality and high tensile and bending strength in the boards to be produced, it is necessary that in completed boards no variations occur in the surface weight and that the material be regularly distributed along the entire length and width of the boards. It is desirable that the boards have largely the same specific weight and a regular unit of area-related structure.
The importance of a regular distribution of pouring material along the width of complete boards may be illustrated with an example from the practice of the production of casing concrete elements according to the Thermoform/Thermoklith-process. In this production process, 2.times.0.5 m wood wool cement-construction boards (WWC-boards) are divided in the longitudinal and transversal direction such that four 1.times.0.25 m basic parts are formed. Next, these basic parts arc interconnected in pairs and in parallel to each other using steel spacers pressed into the sides of the basic parts. Because the width distribution of the material in the WWC-boards is not regular enough, two basic parts having a higher density and two basic parts having a lower (too low a) density are obtained after dividing a WWC-board. In the basic elements having a density that is too low, either the spacers experience hardly any or no grip and will loosen up or pieces will break away from the boards while the spacers are pressed in. This leads to rejection of these elements. A constant and regular width distribution of the material in the WWC-boards would lead to reducing the rejection percentage of the complete Thermoform/Thermoklith-casing concrete elements to a minimum.
In the production of wood particle boards and wood fiber boards, one usually, in a metered manner, supplies the pouring material to a traveling mould belt from a bunker through at least one distributing device. With such devices one usually employs a method of metering the pouring material using a weight or volume control of the layer of pouring material distributed onto the mould belt or a combination of both controls. A corresponding method and device are described in DE-C-1,048,691. From a supply bunker, pouring material is led to a metering belt where, at some distance above the metering belt, a counter-acting scraping drum creates an intermediate supply of pouring material by rotating in the opposite direction and volumetrically meters this pouring material. The metering belt transfers this pouring material, in a metered manner, to a weighing belt by controlling the traveling speed of the metering belt using a control device, such that the amount of material on the weighing belt remains constant in respect of its weight. The weighing belt conveys the material with a constant speed such that a regular amount of pouring material is supplied to the mould belt distributed as a regular layer.
A device in correspondence with the above method can supply a constant stream of pouring material to the mould belt because of a weight or volume control of the distributed layer. Even with a compressible pouring material which rapidly experiences compressions, such as those used for the production of cement-bonded particle boards, regular metering and distribution of the pouring material into the moulds is possible by using an intermediate supply bunker, but only if, with a constant supply of material, the level of pouring material in the intermediate supply bunker also remains, as much as possible, constant in time as well as constant transver
REFERENCES:
patent: 4557882 (1985-12-01), Arnold
patent: 4703783 (1987-11-01), Buksek
patent: 4847022 (1989-07-01), Bold
Bau- und Forschungsgesellschaft Thermoform AG
Raevis Robert
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