FR2715958A1 - Wooden moulding panel for manufacture of concrete slabs - Google Patents

Abstract

The wooden panel used in presses for the manufacture of moulded concrete is assembled by gluing successive wooden planks which are oriented in the direction of their fibres. The planks are brought together and held by two press plates. Glue is applied on one or both sides of each plank, which may or may not be provided with grooves, by passing a gluing roller over them. A bi-directional pressure, perpendicular to the wooden planks under the press and perpendicular to the plane of the moulding panel, is applied on the glued battens preventing their movement. A high frequency current is applied in the glued joints between successive planks to cause polymerisation of the joint glue.

Description

WOODEN PANEL ASSEMBLED BY HIGH FREQUENCY
FOR THE CONCRETE PREFABRICATION INDUSTRY
The release panel is used as a mold base in the manufacturing of vibrated and non-vibrated concrete products. The products can be concrete blocks. (or blocks). free or self-locking blocks. gravel or not. curbs of all types wtoirv aisles ..) as well as any other concrete object made of one or more materials (mass with or without facing) intended for urban planning and decoration. in any site. for assay collets only for individuals.

In b production line for concrete products. the release panel itervbnt significantly on the final product quality To obtain high quality and high density products. the release panels must be perfectly flat. without haze effect or surface defect. The assembly of the various constituent elements must be able to resist.

without any deviance, alternating humidity and drying in the ovens, temperature changes. as well as the transmission of vibrations from the machine to the concrete product. The release panels are extremely stressed. The object of this patent relates to an assembly system capable of simultaneously resisting all the physical and chemical parameters which are imposed on it, increasing its mechanical resistance by the same its lifetime.

Whatever the assembly process. the release panels are made up of several edged boards or battens, joined together by their length. These basic components are generally made of coniferous wood (species which varies depending on the region) but any other species can enter the process protected by this patent.
Some users prefer exotic woods. for their high density and high mechanical strength.

Nowadays. two assembly systems are particularly used for this kind of product:
Assembly by dovetail and assembly by profile and transverse metal tie rods.

The dovetail assembly is the only one used so far in France for this kind of product. It is a mechanical type assembly. like the one we used ten years ago to make coffins. This assembly is carried out on a paneling machine. capable of producing a conical profile. pluggable and pluggable in one direction only However. the system has many flaws: assembly being purely mechanical. the profile works and changes with the alternation of humidity and drying undergone by the panel during the manufacturing cycle of the molded products. The dovetail then moves away. and two phenomena can occur: the separation between two successive boards causes a defect in the concrete product molded on the panel: or the panel. weakened. is disjointed. and became permanently unusable.

Notching the wood to make a profile such as the fragile dovetail makes the board thick. and this embrittlement often causes the breakage of the panel on the joint. This phenomenon is accentuated today because the paneling capable of producing these profiles are very old. It is therefore increasingly difficult to obtain regular and well-fitting prdlls with these machines.

On the other hand. Assembly by profile and transverse metal tie rods poses the problem of the difference in behavior between the Wood Material and the Metal Material. the metal ties which cross the thickness of the panel come out on both sides of this. the presence of this metal can cause incidents in the metal rails during transfers to concrete presses, or even cause short-circuits Finally, this system requires that the panel be pierced in its thickness, which. here again. questions the mechanical resistance of solid wood.

All the above-mentioned manufacturing methods are not satisfactory. it seemed interesting to conduct research on other assembly techniques.

All this research has led to the development of a bonding system. The object of this patent is therefore explicitly the association for a given function, here the release panels. of two materials put under specific conditions, in the present case a 1BOlS material "and a GLUE material". The importance of the intrinsic qualities of the release panel with regard to these geometric characteristics is evident in the manufacturing process of concrete products. It is therefore necessary to pay particular attention to the use of the various materials during the manufacture of the release panels.

The different assemblies resist the following constraints: - Temperature variations between 0 and 80 "C depending on the seasons and the regions (these temperatures will be effective at humidity levels up to 95%) - Alternating humidity cycles and drying (variation of approximately 75%) over a maximum duration of 24 hours.

- High mechanical stresses due to the application of vibrations on the main table of the machine.

The prefabrication presses are equipped with vibrators on each side and under the panel
The vibrations can vary in intensity from 0 to 60 kN. The motors that cause these vibrations operate at a speed of 1,500 to 4,700 rpm.

Each panel undergoes the vibrational movements of two or three synchronous motors synchronized so as to obtain a unidirectional vertical vibration. This makes it possible to say that the attack of the vibratory waves is always made perpendicular to the joint pbn The prefabrication presses exert a force centered on the release panel from 0 to 15 tonnes. which can generate a significant bending stress.

 The process that we implemented to reach such resistances Siors initial conditions is a bonding of the wooden strips and drying under press (or column) at high frequency. The basic principle is to glue the battens. press them to keep them in position and allow the glue to pass through a high frequency current to cause it to polymerize.

Passage of a glue roller on the edges. or gluing with a brush or by spraying.

or any other type of glue existing or to come.

- The wooden sticks thus glued are brought into contact by a mechanical system. This system can be either pneumatic. oleo-hydraulic, electric or manual.

- The battens thus brought together undergo bi-directional pressure. preventing any movement of the board components. that is to say a pressure perpendicular to the edges of the boards under press. and perpendicular to the plane of the release panel.

- When b lower table and the upper plate of the press exert their vertical thrust on the battens, power is applied. High frequency current is applied.

The panel is perfectly surfaced at the exit of high frequency press. without the need to make any changes. However, a surface treatment (planing, sanding, or any other treatment) can be applied if the panel was necessary.

Its characteristics and its dimensional stability independent of any hygrometric or thermal variation allow it to be assimilated to solid wood.

 It is possible to make a groove or a profile on the raw battens. to increase adhesion by increasing the bonding surface. If it is not necessary to groove the board before gluing it, the full mechanical strength will be preserved, avoiding stress concentrations due to the absence of failure initiation. When using the adhesive, its temperature rise increases its viscosity. this penetrates into the wood fibers. by giving it the characteristics of a continuous and homogeneous medium.

The process of gluing the boards by high frequency is able to ensure a final assembly.

Obtaining a continuous medium assimilates the assembly to solid wood. The user is certain by this type of implementation that he no longer knows the problems of dislocation of the panels in his installations without compromising the mechanical and vibrational qualities of the board.

The following alternatives are proposed as possible extensions of bonding techniques. therefore as extensions of the initial patent here notified.

The initial deposit should be extended to all bonding processes currently known or to come.

whatever the type of preparation of the surfaces to be bonded, allowing to restore from wooden battens panels whose mechanical resistance will be equivalent or superior to that of solid wood. regardless of the type of petrol used.

By way of non-exhaustive example, mention may be made, among the methods currently known, of hot water bonding and all of the cold bonding methods.
The same result is also obtained using HotMeL type adhesives
The initial patent filing must be extended to all categories of existing or future adhesives.

 namely: - Urée-Formol adhesives, and all derivatives.

- Resorcin glues, and all derivatives.

- Vinyl glues. and all derivatives.

- Phenolic glues. and all derivatives.

- Polyurethane adhesives. and all derivatives.

- Acrylic adhesives. and all derivatives.

- Epoxy adhesives, and all derivatives.

And in general. all other adhesives or substitute products which could make it possible to obtain a result equivalent to the process used.

And this. whatever their application process. their dosage or their origin with or without hardener. thermosetting or not. single-component or multi-component. whatever their hardening mode, their drying mode. their hot melt or their non hot melt.

Claims (5)

1) - Wooden release panel for the use of prefab presses for molded concrete products. characterized by an assembly system by gluing of successive wooden strips arranged in the direction of the wood fibers. 2) - Release panel according to claim 1 characterized by an assembly by thin enjoined bonding (Fig 1). 3) - Release panel according to any one of the preceding re-endaations, characterized by the application of an adhesive or a substitute product on one or both fields of each strip. Previously grooved (s) or not, by the passage of a gluing roller, or with a stiff brush, or by spraying, or by any other means allowing to glue a strip of wood. 4) - Release panel according to any one of the preceding claims, characterized by mechanics. pneumatic, oleo-hydraulic. electric or manual 5) - Demoulding panel according to any one of the preceding claims. characterized by the application on the glued battens of a bi-directional pressure, preventing any movement thereof. or a pressure perpendicular to the edges of the boards under press. and perpendicular to the plane of the release panel. 6) - Release panel according to any one of the preceding claims. characterized by the application of a high frequency current in the adhesive joints between two successive battens.