Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
2001-03-30
2003-07-15
Crispino, Richard (Department: 1734)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S228000
Reexamination Certificate
active
06592694
ABSTRACT:
BACKGROUND OF THE INVENTION
Sandwich elements have been commonly used in buildings and in ships for many years. They were first used in the form of thin concrete layers separated by an isolating layer, the core. Very often there was a mechanical connection between the concrete layers because the core usually could not transfer the forces necessary for holding the element together. Later sandwich elements were introduced in which the surface layers were made of thin layers, e.g. sheet-metal or laminate. With thin and flexible surface layers, a need arose for rigid cores which were able to transfer forces. This need could be met with cellular plastics, but the need, especially for fire protection and sound isolation, led to mineral wool becoming an important core material.
To make the mineral wool core rigid enough it is sometimes sufficient to increase its density. However it is more customary to change instead the orientation of the fibres in the core so that the main direction of the fibres is orthogonal to the surface plane. Using such a fibre orientation, allows the board to withstand deformation better when it is loaded orthogonally to its plane compared to a mineral wool core that is not reoriented. Reorientation can be carried out using a so called lamina technique, i.e. the normal hardened mineral wool boards are divided into narrow strips, which are rotated 90° around their own axis and assembled in a new sheet-type construction. Other techniques for carrying out the reorientation also exist.
Development has since moved towards using sandwich elements in which e.g. sheet-metal is used as a surface layer not only in partition walls as before, but also in outer walls and roofs. This has placed much higher demands on the quality of the elements, in terms of both appearance and especially strength characteristics, while at the same time the dimensions of the elements also increased many times over previous dimensions.
The principle of manufacturing sandwich elements of this kind is described in WO 98/42503.
The glue that attaches the core to the surface layers is preferably of a thermosetting type, but it may also be self-curing or hardened by some other means, e.g. ultrasound. In a press operation, if needed during heating or other procedure, the surface layers are attached to the mineral wool layers and the glue is cured. When manufacturing sandwich elements, the pressing measure is usually controlled by being carried out against a stopping block which defines the distance between the pressing plates and thereby the thickness of the element during the pressing.
This method can give a poor result when using thin sheet-metal, with faults such as rough surface layers and weak glue joints. Functionally this causes visual problems, because even small roughness in the form of ripples and bosses are clearly visible, especially on totally smooth elements. The strength also deteriorates, which usually is not permissible. To eliminate these problems, the amount of glue, the thickness of the surface layers, the density of the mineral wool layer, the binding agent concentration etc. has been increased or the surface has been additionally machined. Additional glue and binding agent contents result however in inferior fire properties. Another fact is that the product will be much more expensive, and, besides, the result is often not good enough or predictable. Not the least serious problem is, that more expensive measures have to be taken also on elements which have no obvious weaknesses.
In the light of this, extensive and thorough studies and experiments have been made, which have given rise to the invention according to WO 98/42503. According to this publication, the pressing, when needed under heating, is not carried out against a stopping block to a predetermined thickness, but by using a pressure within a predetermined range, P
max
−P
min
, the size of which is determined by the included components, the mineral wool laminas, the surface layers and the glue. In this case both the terminal points of the interval are determined by two different phenomena: the lower limit for the pressing pressure being the lowest pressure needed so that no adhesion breakage will occur; the upper limit being determined by how much the core material withstands while retaining its structural properties.
An important problem remains in this known method, i.e. how the pressing pressure can be kept locally within these limits over the press platen. The problem is accentuated by the reorientation of the mineral wool core, which causes systematical variations between different parts of the core, irrespective of the system used to achieve reorientation. One reason for this is the strength requirement of the element. The core construction must not be destroyed by overpressing, but, on the other side the attachment of the top layer must be guaranteed. The visual appearance of the element is also of importance since the human eye is disturbed by even very small bosses on the surface of the element.
SUMMARY OF THE INVENTION
Yet another problem with the pressing method lies in the flatness and parallelness of the press platens. Usually the structures are huge, sizes of up to 15 m
2
not being unusual, and the demands often include a requirement that deviations from smoothness and parallelness shall be less than 0.2 mm. The press platens are usually also heated and problems especially arise with traditional presses in which the displaceable press platen often becomes slightly bent.
The invention solves the aforesaid problems with a method and an apparatus according to the accompanying patent claims.
When thin surface layers, e.g. made of sheet-metal, must be attached to a core made of reoriented mineral wool in a sandwich element, according to the invention a laminating apparatus is used in which at least one of the press platens is flexible and is acted on by many power units, the influence of which can be controlled individually or in groups, it then being possible to control the pressing pressure in different parts of the press platen and keep it within the aforesaid limits P
max
−P
min
.
In the simplest embodiment the other press platen is fixed and flat.
Before pressing is performed, the power units are usually adjusted so that the flexible press platen becomes flat and preferably also parallel to the other press platen. For this purpose the power units may be double-acting.
In some applications it is preferable that both press platens are flexible and separately acted on by several power units, the influence of which during the pressing can be controlled individually or in groups.
Then the press platens can be formed, in the first instance with a curved cross-section. Both press platens must then be bent in the same direction and by the same amount. The element then becomes accordingly curved or dome shaped, which may be desirable in certain applications. Partly these dome shaped elements give an architectonic effect, partly the dome shape means that smaller deviations from an otherwise regular plane will not be as clearly visible as in the case of a flat element.
In a normal case the influence of the power units shall be controlled in such a manner that both flexible press platens becomes both parallel to each other and flat. As aforesaid, the aim can be elements, which have curved cross-sections and in these cases the press platens must anyway be parallel.
By continuous pressing, the optimal curing of the glue may require the press platens to be flat but convergent or divergent.
For an optimal glue effect it is necessary for the press platens to exert a pressure against the press object within predetermined limits, in which the lower limit is determined by the lowest pressure, Pmin, which is needed so that when tearing apart the connection, adhesive failure will not occur, and the upper pressure, Pmax, is determined by the condition that the proportionality limit of the core material not shall be reached.
The limits are, at their broadest, Pmax and Pmin respectively, but they may also, when t
Brunila Esko
Heselius Lars-Henrik
Willman Tarmo
Connolly Bove & Lodge & Hutz LLP
Crispino Richard
Koch, III George R.
Paroc Group Oy AB
LandOfFree
Flexible belt pressing laminating apparatus and method does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Flexible belt pressing laminating apparatus and method, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Flexible belt pressing laminating apparatus and method will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3026980