Printing plate arrangement in a press

Abstract

Heatable pressure plate arrangement for a continuous press (1) with at least one bendable and heatable pressure plate (8) by means of actuating elements (11, 12, 22, 23) and at least one counter-pressure plate (9), between which a pressing mat (2) that can be inserted in a direction of travel (L) can be compressed and discharged, wherein at least the at least one bendable and heatable pressure plate (8) has channels (24, 27, 28, 29) for a temperature control medium, which comprise at least one inlet channel (27) and one return channel (28), wherein the temperature control medium can be introduced into or discharged from the channels (24, 27, 28, 29) via one or more inlet and outlet connections (25, 26) provided on the pressure plate (8), characterized in that at least one inlet channel (27) and / or at least one return channel (28) in the pressure plate (8) is opposite the The direction of travel (L) of the press mat (2) has an angle Σ between 0.2° and 5.0°.

Description

The invention relates to a heatable pressure plate arrangement for a continuous press (1) having at least one pressure plate (8) which can be bent and heated by means of adjusting elements (11, 12, 22, 23) and at least one counter-pressure plate (9), between which a compressed material mat (2) which can be introduced in a running direction (L) can be compacted and discharged again, wherein at least the at least one bendable and heatable pressure plate (8) has channels (24, 27, 28, 29) for a temperature control medium which comprise at least one inflow channel (27) and one return channel (28), wherein the temperature control medium can be introduced or discharged into the channels (24, 27, 28, 29) via one or more inlet or outlet connections (25, 26) provided on the pressure plate (8).Such a pressure plate arrangement is known, for example, in the production of wood material boards. It is part of a continuous press in which a mat of pressed material scattered from chips or fiber wetted with binders is compacted to form a sheet. Preferably, endless circulating pressing belts, for example steel belts, are provided around the bendable and heatable pressure plate and the counter-pressure plate, which are supported on the pressure plates with the interposition of rolling bodies, for example rolling rods. The mat of pressed material is guided into the pressing gap with the aid of the pressing belts and is guided through the pressing gap and pressed using pressure and heat to form a wood material board or a (continuous) wood material board strand. Wood material board refers in particular to fiberboard or particle board. A fibre board can be, for example, an MDF board or else an HDF or LDF board.The pressure plate arrangement is accordingly arranged within a continuous press. Such a continuous press is known, for example, from DE 102 14 322 B4 or DE 197 40 325 C5. Double-acting differential cylinders are connected to the bendable and heatable pressure plate (in several rows) as adjusting elements, so that tensile and compressive forces for setting continuous bending lines are connected to the bendable and heatable pressure plate or to the lower counterpressure plate in a predefined distribution.In a continuous press, the first pressure plates and counterpressure plates form the so-called inlet mouth in the running direction of the press material mat to be pressed and compacted, as a result of their curvature. The lower and / or the upper pressure plate can be bendable.The printing plates are generally tempered, primarily heated. This takes place via bores made in the pressure plate. The introduction of such deep-hole bores into the pressure plate is known in principle. Whereas it does not matter in which direction the bores are arranged in relatively thick fixed and non-bendable pressure plates, the bores are introduced into the relatively thin plates which are bent toward the inlet mouth in the running direction of the mat of pressed material, i.e. parallel to the longitudinal axis of the plate. If the bores were at right angles thereto, which would enable more uncomplicated lateral supply of a heating medium, the pressure plate would be at risk of bending during the bending. This would be even more critical in the case of the highly modern inlet pressure plates of the applicant if they are lowered and raised cyclically in a pulsating manner, as described in DE 10 2017 110 865 A1.Thus, in the case of current flexible pressure plates, the channels in the interior of the plate run in the running direction of the mat. Because the inlet and outlet connections for the temperature control medium are practically provided only at one end of the pressure plate, this invention refers to inflow and return channels. This means that the inflow channel runs from the inlet connection to the opposite pressure plate end (for example opposite the running direction of the pressed material mat), and the return channel leads from the pressure plate end to the outlet connection (for example in the running direction of the pressed material mat). As a rule, one or two inflow channels are arranged next to one or two return channels. The bores, both for a feed channel and for a return channel, are made over the entire length of the plate, wherein normally only one end of the plate (viewed in the running direction of the pressed material mat being made) is provided with a cross-connection channel. Since the plates are nowadays between 3.0 and 7.0 m long, the temperature control medium, generally heating oil, experiences a sharp temperature decrease from the inlet connection along the inflow channel over the pressure plate length and back again via the return channel up to the adjacent outlet connection. Thus, for example, a heating oil at 260° C. is introduced into the heating plate and comes out again at 255° C., i.e. a relatively high temperature difference. The heating oil inlet usually moves in a temperature range between 180° C. and 300° C.The problem here is that a different energy level can thereby be emitted from one feed channel to the steel strip and thus to the mat of material to be pressed than from an adjacent return channel. In fact, in the case of some pressed material mat compositions, this causes a formation of stripes of different temperatures on the rolling bodies or the revolving steel strip and thus also on the pressed product, which is naturally undesirable. By means of various parameters such as the volume flow of the temperature control medium, component thicknesses, etc., the temperature difference can be reduced to a limited extent, but a homogeneous heat emission state on the pressure plate onto the mat of material to be pressed is never achieved.The object of the invention is to provide a heatable pressure plate which enables more uniform heat emission to the mat of pressed material over its width.The object is achieved with the features of claim 1 and in particular in that at least one inflow channel and / or at least one return channel in the pressure plate has an angle of between 0.2° and 5.0°, preferably an angle of between 0.3° and 1.0°, with respect to the running direction (L) of the pressed material mat.It has been found that this angle adopted is small enough not to jeopardize the plate during the bending, but on the other hand to significantly equalize the energy output to the mat of pressed material over its width. This is because the rolling bodies and the steel strip now pass over both warmer and colder channel points. The angle is also small enough to not generate a dead space that is not heated slightly at the end, i.e. in the reversal region of the pressure plate. The effect is in fact that the rolling bodies and the steel strip pass uniformly over "hot" and "cold" points when moving along the heating plate, as a result of which a better temperature distribution is achieved in the steel strip and the same amount of heat is therefore introduced into the mat of material to be pressed on average over the entire width of the mat of material to be pressed.It is preferred that at least 90% of the return and return channels are arranged in parallel.In this case, it is additionally expedient if the spacing of different forward and return channels is identical.This makes the temperature field on the surface of the printing plate uniform.It is particularly preferred if the offset of the end of a feed channel relative to the end of the feed channel, in which the feed channel is oriented in the running direction of the introduced pressed material mat, has an amount of 20 to 80% of the distance between the feed channel and an adjacent channel.Experiments have shown that in this offset region the best equalization of the heat input into a passing mat takes place. The reversal point from the forward to the return channel is also slightly displaced at one end of the pressure plate in this way. The most effective value of the displacement is dependent on the thickness of the mat of material to be pressed and the passing speed of the steel strip, rolling bodies and mat of material to be pressed.It is advantageously provided that a return channel and a run-in channel overlap at different ends of the printing plate with respect to a longitudinal strip of the printing plate, with the same edge spacing everywhere.In this case, each point of the pressed material mat passes once over a temperature section of a return channel and a temperature section of a run-in channel. In this case, too, the total heat input is equalized.It is advantageous if the spacing of the feed and return channels is between 50 and 150 mm for a pressure plate made of steel and 40 to 150 and preferably 50 to 70 mm thick, and the feed and return channels have a diameter of 30 to 50 mm.Pressure plates with these geometric dimensions have a good bending possibility, especially in the case of the pressure plates 50 to 70 mm thick, with a comparatively economically cost-effective hydraulic arrangement for the adjusting elements. At the same time, a satisfactorily uniform heat input into the compressed material mat can be realized with them.It is furthermore advantageous if all the outward and return channels have a distance from the printing plate surface, measured to its surface-closest point of the outward and return channels, of more than 10 mm and preferably more than 15 mm.This distance has proven to be advantageous in the case of the process heat introduced into the mat nowadays, since the distance assists the aim of sufficiently uniformizing the heat flow rate and the temperature at the surface.In order to be able to react specifically to temperature differences in the pressure plate surface, it is preferably provided that the cross section of a feed channel or return channel is reduced in sections by inserts.By changing the cross-section of the channels, the speed of the heating medium is increased and thus the heat transfer value is also increased. In this way, the heat transfer can be locally changed.For better distribution of the heat emitted from the channels, it is also advantageous if channels have a distance A from the surface of the printing plate, measured to its surface-closest point of the channel, of more than 10 mm and, if possible, even more than 15 mm.As a result, the heat flux fans out further and does not concentrate on a narrow strip above the channel.It is a further object of claim 11 to protect a continuous press having a printing plate assembly according to the invention.The invention is explained in more detail below with reference to drawings illustrating exemplary embodiments. They show FIG. 1 shows a pressure plate according to the invention, which is cut several times and in which the channels for tempering are visible, FIG. 2 shows the pressure plate according to the invention, illustrating the oblique position of the feed and return ducts, FIG. 3 shows the state of the art of a front part of a continuous press, and FIG. 4 shows a detail of a pressure plate.The description of the figures starts with Figure 3 because it represents a continuous press of the prior art in which the invention can be integrated.FIG. 3 shows the front part of a continuous press 1 for pressing mats 2 to form boards during the production of particle boards, fibre boards and other wood material boards. This side view represents the prior art as is known from DE 102 14 322 B4. This press has a lower press part 3 and an upper press part 4, namely with steel press belts 5 continuously rotating in the lower press part 3 and upper press part 4 and with an inlet mouth E. In the lower press part 3 and upper press part 4 there is arranged in each case a heatable press plate 6, 7, of which, according to the exemplary embodiment, the upper press plate 6 can be adjusted against the lower press plate 7 in order to adjust the press gap. The press plates 6, 7 are adjoined by heatable pressure plates 8, 9 projecting on the inlet side, forming the inlet mouth E. The steel pressing belts 5 are supported on the pressing plates 6, 7 and pressure plates 8, 9 with the interposition of rolling rods 10 or similar rolling bodies. Furthermore, a device 11 for setting the inlet mouth E and adjusting elements 12 for setting the inlet contour of the inlet mouth E are provided.The device 11 for setting the inlet mouth E has on both sides of the inlet mouth E in each case at least one roller 13, 14 arranged upstream of the pressure plates 8, 9 for the steel press belts 5 running to deflecting drums 15, 16. Similar deflecting drums to the deflecting drums 15, 16 are present in the rear part of the press 1, so that the steel belts 5 produce closed circuits both in the upper press part and in the lower press part. The rollers are designed as press rollers 13, 14 or pressure rollers and form a pre-compression zone 17 for the incoming pressed material mats 2 which is arranged upstream of the pressure plates 8, 9. The last press roller 13 in the inlet direction upstream of the upper pressure plates 8 is assigned a counter-press roller 14 on the underside of the inlet mouth E. In the inlet mouth E, a transfer conveyor 18 with a transfer nose 19 for transferring the pressed material mats 2 is arranged. Depending on the thickness of the respective mat 2 of pressed material, the transfer nose 19 can be advanced right before the compression region between the last upper press roller 13 and the lower counter press roller 14 in the region of the lower steel press belt 5. In addition, the transfer conveyor 18 can be moved back and forth with its transfer nose 19 by an indicated drive unit 20 with a control or regulating device 21 depending on the properties of the material to be pressed, the spreading density, the mat density, the plate thickness to be produced, etc. in the horizontal and vertical directions. This is indicated by arrows. The device 11 for adjusting the inlet mouth E with the upper press rollers 13 in the pre-compression zone 17 can be pivoted in and out via cylinder piston arrangements 22 arranged articulated on both sides. The upper press rollers 13 are arranged in series next to one another and form with the abutting steel press belt 5 a predetermined inlet radius which is maintained when the press rollers 13 are pivoted in and out depending on the respective thickness of the press material mats 2. The adjustment of the inlet contour of the inlet mouth E by the adjusting element 12 takes place in the region of the pressure plates 8, 9 by means of double-acting actuating cylinders 23 arranged in a predefined distribution and optionally individually controllable.The pressure plates, i.e. both the upper pressure plate 8 in the press upper part 4 and the pressure plate 9 in the press lower part 3, are bendable and heatable pressure plates in this exemplary embodiment. However, within the scope of the invention, only one flexible pressure plate 8 should also be sufficient.FIG. 1 illustrates the heatable pressure plate 8 which is novel compared with the prior art in a plurality of sectional views of the one pressure plate 8, the reference sign for the pressure plate being denoted by 8 below, wherein the invention would also be usable for the pressure plate denoted as counter-pressure plate 9 in the prior art. In the lower part of FIG. 1, the pressure plate 8 is shown in a side view. An inlet connection 25 for a temperature control medium can be seen. Immediately above this, FIG. 1 shows the section, designated A-A, through the pressure plate 8 at half the height, whereby the individual channels 24 become visible. A single piece is cut out of the pressure plate 8 shown in FIG. 1 in the middle, because the channels 27, 28, 29 in a true-to-scale embodiment would be difficult to see in section A-A.The heatable pressure plate 8 has channels 24, 27, 28, 29 running in the interior, wherein the inflow channels 27 and the return channels 28 have been produced by deep hole bores in this exemplary embodiment. At the end of the pressure plate 8 opposite the inlet ports 25 and outlet ports 26, the inflow channels 27 and the return channels 28 are connected by a cross-connection channel 29. The cross-connection channel 29 is milled, for example. The openings of the channel system, which have been formed by drilling or milling, are tightly welded before the pressure plate 8 is installed in the continuous press 1.Apart from the inlet connections at the edges of the pressure plate 8 (which, however, can also be outlet connections), two channels 24 emerge from all other inlet connections 25 and outlet connections 26.During the flow of the temperature control medium through the pressure plate channels 24, there is heat released to the pressure plate. As a result, the temperature control medium in the supply channel 27 has a temperature that is up to 5° C. higher than in the return channel 28, which temperature differences can become noticeable as stripes on the surface of particularly sensitive products, which is naturally undesirable. The situation becomes even more extreme if-as likewise explained in the exemplary embodiment-apart from the channels 24 on the side of the pressure plate 8 completely outside-even two inflow channels 27 are located next to two return channels in each case, in order to save inlet and outlet connections.For this reason, the feed channels 27 and the return channels 28 are introduced into the pressure plate 8 at a slight angle of 0.2° to 5.0°, preferably between 0.3° and 1.0°, with respect to the running direction L of the mat of pressed material. This leads to an offset V of the channels 24 at different points in the running direction L, as can be clearly seen on the exemplary sections B-B and C-C on the right-hand side of FIG. 1. Thus, all the rolling elements 10, the steel press belt 5 and also the press material mat 2 pass over both warmer and cooler points on the surface of the pressure plate, which leads to an effective heat transfer compensation.In FIG. 2, the guidance of the channels 24 is schematically shown in a simplified manner. The channels are indicated only by a line corresponding to the central axis of the bore. Since the running direction L of the mat of pressed material generally corresponds to the side edge of the pressure plate 8, the angle α is shown here simply between a first channel, for example a run-in channel 27, and the longitudinal side of the pressure plate 8. However, the same angle α would also be indicated between the center line of the pressure plate 8 (shown in dash-dot lines) and every other channel 24, since all the inflow channels 27 and all the return channels 28 run parallel and at the same distance in this exemplary embodiment.The cutout 32 is provided for the deflection devices of the rolling bodies only and has no further significance for the invention.Finally, FIG. 4 shows a detailed cross section of the pressure plate 8, wherein a channel 24, i.e. for example a run-in channel 27 or a return channel 28, is provided with an insert 30 at least in places. As a result, the cross section for the temperature control medium is reduced, which leads to an acceleration of the temperature control medium. The heat transfer value of the temperature control medium to the pressure plate can thus be changed in a targeted manner. It is also shown that a greater distance A is provided between the channel and the surface 31. The distance from the surface 31 of the pressure plate to the closest point of the channel 24 is measured. This distance should be at least 10 mm if the distance between the return and return channels is between 50 and 150 mm for a pressure plate made of steel and having a thickness of 40 to 150, and preferably 50 to 70, mm, and the bores for the return and return channels have a diameter of 30 to 50 mmList of reference characters1 Continuous press 2 Press material mat 3 Press lower part 4 Press upper part 5 Steel press belt 6 Heatable press plate 7 Heatable press plate 8 Heatable press plate 9 Counterpressure plate 10 Rolling bodies, rolling rods 11 Device for adjusting the inlet mouth 12 Adjusting element for adjusting the inlet contour 13 Roller 14 Roller 15 Deflecting drum 16 Deflecting drum 17 Pre-compression zone 18 Transfer conveyor 19 Transfer nose 20 Drive unit 21 Regulating device 22 Cylinder piston arrangement 23 Actuating cylinder 24 Channel for temperature control medium 25 Inlet connection for temperature control medium 26 Outlet connection for temperature control medium 27 Inflow channel 28 Return channel 29 Transverse connection channel 30 Insert 31 Surface 32 Cutout E Inlet mouth L Running direction V Offset A Distance Channel to the surface α Angle

Claims

Heatable pressure plate arrangement for a continuous press (1) having at least one pressure plate (8) which can be bent and heated by means of adjusting elements (11, 12, 22, 23) and at least one counterpressure plate (9), between which a compressed material mat (2) which can be introduced in a running direction (L) can be compacted and discharged again, wherein at least the at least one bendable and heatable pressure plate (8) has ducts (24, 27, 28, 29) for a temperature control medium which comprise at least one inflow duct (27) and one return duct (28), wherein the temperature control medium can be introduced or discharged into the ducts (24, 27, 28, 29) via one or more inlet or outlet connections (25, 26) provided on the pressure plate (8), characterized in that, at least one feed channel (27) and / or at least one return channel (28) in the pressure plate (8) has an angle α between 0.2° and 5.0° with respect to the running direction (L) of the mat (2) for material to be pressed.Heatable pressure plate arrangement according to claim 1, characterised in that the adjacent outward and return channels (27, 28) in the pressure plate (8) have an angle between 0.3° and 1.0° with respect to the running direction (L) of the pressed material mat (2).Heatable pressure plate arrangement according to claim 1 or 2, characterised in that at least 90% of the feed and return ducts (27, 28) are arranged in parallel.Heatable pressure plate arrangement according to one of Claims 1 to 3, characterized in that the spacing between different inflow and return ducts (27, 28) is identical.Heatable pressure plate arrangement according to one of Claims 1 to 4, characterized in that the offset of the end of a run-in channel (27) with respect to the end of the run-in channel, in which the run-in channel is aligned in the running direction of the introduced pressed material mat, has an amount of 20 to 80% of the distance between the run-in channel (27) and an adjacent channel (24, 28).Heatable printing plate arrangement according to one of Claims 1 to 5, characterized in that a return channel (28) and a run-in channel (27) at different ends of the printing plate (8) overlap with respect to a longitudinal strip of the printing plate (8) which has the same edge spacing overall.Heatable pressure plate arrangement according to one of Claims 1 to 6, characterized in that the distance between the axes of the inflow and return ducts (27, 28) is between 50 and 150 mm in the case of a 40 to 150 mm thick steel pressure plate (8), and the inflow and return ducts (27, 28) have a diameter of 30 to 50 mm in this case.Heatable pressure plate arrangement according to one of Claims 1 to 6, characterized in that the distance between the axes of the inflow and return ducts (27, 28) is between 50 and 150 mm in the case of a pressure plate (8) made of steel and having a thickness of 50 to 70 mm, and the inflow and return ducts (27, 28) have a diameter of 30 to 50 mm in this caseHeatable pressure plate arrangement according to one of Claims 1 to 8, characterized in that, in at least one section, the cross section of a feed or return duct (27, 28) is reduced by an insert (29).Heatable pressure plate arrangement according to one of claims 1 to 9, characterised in that channels (24) have a distance (A) from the surface (31) of the pressure plate (8), measured to its surface-closest point of the channel (24), of more than 10 mm, preferably more than 15 mm.Continuous press for producing wood-based material boards, characterized in that it has a pressure plate arrangement according to one of Claims 1 to 9.

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