FR2511934A1 - HOT PRESSING SYSTEM FOR BUILDING WOOD-BASED PANELS - Google Patents

Abstract

The invention relates to a system for hot-pressing material to form wood-based boards in the course of the production of chipboards, fibreboards and the like. The hot-pressing is carried out in a platen press with permanently heated press platens, which press platens have, in two platen planes of their platen thickness, heating-channel systems with heating channels parallel to one another through which a heating medium flows. The two heating-channel systems of each press platen can be independently open-loop controlled and/or closed-loop controlled as regards the flow rate of the heating medium with the aid of an open-loop and/or closed-loop control device. One of the heating-channel systems of each press platen is located in the press-platen centre plane. The other heating-channel system is arranged in that half of the press-platen thickness which is connected to the press-platen centre plane at the side towards the material to be pressed. Otherwise, the design is such that the open-loop and/or closed-loop control device only supplies the heating-channel system in the press-platen centre plane with the heating medium during heating of the press platens, however during operation of the press, the heating medium is switched over to that heating-channel system of the press platens at the side towards the material to be pressed. In this manner, the distortions in the press platens themselves caused by heat stresses can be compensated for or completely avoided, with simple open-loop and/or closed-loop control outlay.

Description

 The invention relates to an installation for hot pressing of material with a view to making wood-based panels such as chips, fibers, etc., compressed on a press (with one or more stages) with permanently heated plates, each of these plates having, arranged in two planes of its thickness, heating channel systems parallel to each other and traversed by a heating fluid, these two channel systems of each plate being able to be controlled and / or regulated differently (as far as fluid flow) using a control and / or regulation device.

 In known installations belonging to this type, the plates or plates of the press are, from the mechanical and thermodynamic point of view, integral parts of a box-shaped supporting frame to which belong the webs of beams which are welded to the plates of the press to which they are perpendicular, and closing plates parallel to the plates and welded to the webs of side members (patent No. 16 53 185 in Germany). The souls of longermons, as well as the closing plates, present systems of heating channels. The control and regulation device controls the supply of the various heating channel systems so that, during pressing, the press plates or plates remain flat and mutually parallel. This requires a very complicated set of measurement and regulation means. and important. In general, simple temperature measurements on the press platens are insufficient for control and / or regulation. Measuring devices controlling thermal deformation are required, and the measurements thus obtained must be introduced into the command and / or regulation device. Despite this, it is frequent that, during pressing, the press plates are not sufficiently flat and parallel to each other. In fact, in the known prior embodiment, it is not intended to compensate for the deformations due to thermal stresses, deformations which are due to the fact that the plates must, during pressing, yield heat to the pressed material, so that the trays are themselves the seat of a gradient.

 The object of the invention is to reduce the complexity of the control and / or regulation in the case of an installation of the type under consideration, and, for this, to compensate in the plates or trays themselves the deformations due to thermal stresses. or even prevent them from being born.

 To achieve this object, the invention recommends that one of the heating channel systems of each press plate is arranged in the median plane of this plate, and that the other channel system is arranged in that of the halves of the press. thickness of this plate which, relative to said median plane, is located on the material to be pressed side, and that the command and / or regulation device only supplies heating fluid, during the heating of the plates, to channel systems located in the median planes of these plateaus and. causes, during the press work, the supply of heating fluid to the heating channel systems that the plates comprise on the material to be pressed. The invention starts from the recognition of the fact that, in the case of an installation of the kind considered, intended for hot pressing of panels made of wood-derived materials, the press plates can be heated without deformation due to thermal stress, if the heating is carried out using a system of channels located in the plane of each tray. It goes without saying that the beams or box springs must not apply any disturbing mechanical stress to the press plates. This result can be obtained without difficulty by establishing appropriate degrees of freedom. In this context, the invention recommends that, with respect to the press bases which are combined therewith, the press plates are arranged with the possibility of performing the movements. due to their thermal expansions, the expression "when working the press does not only mean the pressing times but also the whole period during which the continuously heated press operates in opening and closing after the warming up.

 The invention includes developments which differ according to the particular operating conditions, the constitution of the material to be pressed and the press timing times. Thus, a preferred embodiment is characterized by the fact that, during pressing, the control and / or regulation device only supplies heating fluid to the heating channel system that the press plates have on the material side. press. If necessary, the command and / or regulation device can also supply, in addition, heating fluid to the system of channels that the plates have in their median planes.

In general, by operating as described, the perfect flatness and the plane-parallelism of the plates of an installation according to the invention are maintained, the control requiring - as indicated below - only temperature measurements on the press platforms. It is furthermore within the scope of the invention to produce an arrangement such that the command and / or regulation device leads to the production of a heating countering the deformations by applying heating fluid to the system of channels which the plates comprise in their median planes, the heating countering the deformations (anti-deformation heating) of the plates or press plates is known per se.

 The advantages achieved lie in particular in the fact that, in the case of an installation of the type considered, the deformations inherent in thermal stresses are compensated for, or even prohibited, which significantly reduces the complexity of the control and / or regulation .

 The description which follows, with reference to the accompanying drawings by way of nonlimiting examples, will make it possible to understand clearly how the present invention can be put into practice.

 Figure 1 schematically shows an elevational view of the plate press of an installation according to the invention, and shows the channel systems in the plates or plates of the press.

 Figure 2 shows the object of Figure 1 during the heating of the plates.

 Figure 3 shows the object of Figure 1 during pressing.

 FIG. 4 shows, on an enlarged scale compared to FIGS. 1 to 3, a sectional view along A-A of FIG. 3.

 The installation shown in the figures is used for hot pressing of material 1 with a view to making compressed panels made of materials derived from wood. The material 1 to be compressed may, for example, be intended to constitute panels of chips, fibers, etc. The hot pressing is carried out in a plate press, which is mono-stage in the present example and comprises plates or pressing plates 3 which are continuously heated. These pressing plates 3 have, in two planes located in their thickness, 4.5 systems of heating channels 6,7 parallel to each other and traversed by a heating fluid.

The heating fluid is supplied via lines 8, 9. The two heating channel systems 4, 5 of each plate 3 of the press can be controlled or regulated differently, as regards the flow of heating fluid, using a known control and / or regulation device. per se, not shown.

 A comparative examination of FIGS. 1 and 4 shows that the first system 4 of heating channels of each plate 3 of the press is located in the median plane of this plate, while the other system 5 is located in that of the half thicknesses of the plate which, with respect to the aforementioned median plane, is located on the material side to be pressed.

 In FIG. 2, lines drawn in strong lines show that, during the heating and heating of the plates 3 of the press, the command and / or regulation device only supplies heating fluid to the system 4 of channels in the plane median of each tray. The plate press 2 is open and no material to be pressed is found in this open press 2. On the other hand, in the case of FIG. 3, material 1 to be pressed has been introduced into the press 2 and the latter is closed. In this figure, the solid lines show that the command and / or regulation device then brings, during the working of the press, the heating fluid only to the system 5 of heating channels which, in the platens of the press, is located side material to compress.

 FIGS. 3 and 4 considered together show that it is also possible, without problem, to supply heating fluid to the system 4 of channels in the median planes of the plates 3 of the press. One could also, suitably carry out a heating countering the deformations. In general, in such an installation, the plates or plates 3 of the press will be arranged so that they can accomplish the movements due to thermal expansion relative to the bed bases 10 of the press.

Claims (5)

 1. - Installation for the hot pressing of material with a view to making panels of wood derivatives such as chips, fibers, etc., compressed on a press with permanently heated plates, each of these plates having, arranged in two planes of its thickness, heating channel systems parallel to each other and traversed by a heating fluid, these two channel systems of each plate being able to be controlled and / or regulated differently using a control device and / or re regulation, this installation being characterized in that, for each plate (3) of the press, one (4) of the systems (4,5) of heating channels is arranged in the median plane of this plate, and l 'other system (5) in that of the thickness halves of this plate which, relative to said median plane, is located on the material side to be pressed, and by the fact that the control and / or regulation device, during the heating of the plates (3), feeds only the systems (lut) of c anal located in the median planes of these plates and, when working the press, causes the supply of heating fluid to the systems (5) of heating channels that the plates have on the material side to be pressed.  2. - Installation according to claim 1, characterized in that, relative to the press bases (10) which are combined with them, the plates (3) of the press are arranged with the possibility of carrying out the movements due to their expansions thermal.  3. - Installation according to claim 1 or 2, characterized in that during the work of the press, the control and / or regulation device provides heating fluid only to the system (5) of heating channels that the plates include side of the material to be pressed.  4. - Installation according to claim 3, characterized in that, when the press (2) is open, the control and / or regulation device also supplies heating fluid to the system (lut) of heating channels as the plates ( 3) include in their median planes.  5. - Installation according to claim 1 or?, Characterized in that it is for heating against deformations that the command and / or regulation device applies heating fluid to the system (4) of channels that the trays have in their median planes.