AT14312U1 - Device for cooling moving flat material - Google Patents

Abstract

The invention relates to a device for cooling moving flat material (2) from a mixture of preferably lignocellulosic and / or cellulosic particles, in particular HDF and UTHDF plates, or MDF and UTMDF plates, which are mixed with binders, following one hot, compacting production process, wherein the cooling via at least one circumferential, the flat material (2) in operation in the direction over a length of at least 100 mm contacting surface of a revolving belt (7) or a circumferential roll shell of a cooling element (4) is vornehmbar, wherein the circulating belt (7) or the rotating roll shell can be acted upon by a cooling fluid on the inside and can be pressed against the flat material (2) under a contact pressure. In order to realize a faster and more accurate manufacturability, it is provided that the contact pressure and / or the cooling power can be applied via a plurality of zones (16) of at least one element (9) arranged transversely to the running direction of the flat material and independently controllable.

Description

description

DEVICE FOR COOLING MOVING FLAT MATERIAL

The invention relates to a device for cooling of moving flat material auseinem mixture of preferably added with binder lignocellulosic and / or cellulose-containing particles, in particular HDF and UTHDF plates, or MDF and UTMDF plates, followed by a hot, compacting production process, the cooling over at least one circumferential, the flat material in operation in the direction over a length of at least 100 mm contacting surface of a circulating belt or a Umlaufenden roll shell of a cooling element vornehmbar, wherein the circulating belt or the rotating roll shell can be acted upon on the inside with a cooling fluid and under a contact pressure against the flat material is pressed.

The production of HDF and UTHDF or MDF and UTMDF plates takes place in a hot compacting manufacturing process. MDF stands for a medium density wood fiberboard or medium density fiberboard, while HDF refers to the high density fiberboard. More specifically, the invention relates to sheet having a thickness of 1 to 5 mm and a density of 600 to 1200 kg / m3. At this point the thickness designation comes the intent in the designation, the UT, to bear, the "Ultra Thin" characterizes. The desired production rate should be able to reach up to 2 m / s.

So far, such plates have been insufficiently cooled with air or Wasserbeaufschlagung. Apart from the fact that the cooling section in this case is very long and has a pronounced high energy consumption, such processes also result in immernegative influences on the recently smoothed surface or effects on the chemical or physical structure of the flat material.

From DE 199 19 822 A1 and DE 199 26 155 A1 double-belt cooling presses are known, through which an approximately 15 mm thick material plate can be subjected to shock cooling. It can be seen from both publications (particularly detailed in FIG. 2 of DE 199 26 155 A1) that core temperatures of 80 to 100 ° C. can be achieved. It is known that, after such a treatment, material panels often have to be stored in such a double-belt cooling press for a relatively long time in so-called "cooling stars" until they reach a temperature at which they are stackable. Or the boards need to be ground in similar installations because the surfaces are roughened.

Particularly serious - and especially with thin sheet material according to the invention - is when it comes in the production process to density or thickness variations in the transverse profile. In the case of UTMDF / UTHDF flat material, the unevenness can arise due to fluctuations in both scattering, ie they are variations in basis weight. These are even in the order of 10 kg / m3 with a mean plate density of 860 kg / m3. It would be unavoidable when using the latter double-belt cold press alone that the (UT) MDF or (UT) HDF boards become wavy when stacked sections are cut. In addition, if the stacking occurs, if the temperature of the sheet is still too high or too high a gradient from the core to the surface, the binders may also change over time and adversely affect the mechanical properties.

In any case, plates of uneven thickness or density must be post-processed, which consumes a non-negligible production time.

The object of the invention is therefore to provide an apparatus with which a flat material according to the invention can be cooled without significant loss of quality, so that it is faster and more accurate to manufacture than the state of the art allows.

The object is achieved according to the device in that the contact pressure and / or the cooling power over a plurality of transversely to the direction of the sheet material arranged andunabhängig each other controllable zones of at least one element can be applied.

The cooled belt or the cooled jacket have a significant influence on the forming surface quality of the sheet. If pressure or temperature can be adjusted zone by zone over the width of the sheet or in its machining direction, one can skilfully influence the profile. For example, it may be necessary to operate at drier edge zones of the flat material with different pressures or temperatures than that which is applied in the center of the flat material. Unevenness in the flat material can also be compensated, for example in the transverse profile transversely or in the longitudinal profile in the direction of the flat material caused thickness variations. For MDF / HDF sheet, as noted, the unevenness could be due to variations in scatter, so they are basis weight variations. These are even in the order of 10 kg / m3 at an average plate density of 860 kg / m3, even in the case of modern plants. The pressure in the individual zones can be controlled via a processor, for example, based on the thickness differences determined by a sensor.

It is advantageous if the element is a pressure element which presses the rotating belt or the rotating roll shell against the sheet. Thus, one possesses an element which is capable of applying the base pressure to the tape or cladding. About the zones then only the local pressure increases or Kühlleis¬tungsveränderungen must be effected. Preferably, the pressure element is provided within the Küh¬lelementes to press the rotating belt or the rotating roll shell against the flat material. Such a pressure element can be adapted in its elasticity and Reib¬werten.

Preferably, the zones are narrower in the region of the flat material edge transversely to the direction of the flat material than in the middle. This gives a finer Profilierungsmög¬lichkeit on the edge, where usually the largest deviations from the nominal profile occur. In addition, there is the possibility of being able to treat also different widths of fiber material by the outermost zones are switched on or off accordingly.

It is advantageous if the zones comprise hydrostatic pockets. On the one hand, hydrostatic pockets make it possible to build up a pressure which greatly reduces friction in the case of two parts which can move relative to one another (band or jacket to the element). On the other hand, the hydrostatic fluid can also be used for cooling.

Particularly preferred is ensured that the contact pressure on the pressure of the cooling fluid can be generated. For example, pressure elements are used which can be operated by one or more piston-cylinder units. The cooling fluid is passed under a pressure of 3 to 20 bar through one or more capillaries into a so-called pressure pocket which is embedded on the surface of the pressure element facing the band or the jacket. The cooling fluid then flows over the framing webs of the pressure pocket and takes over two tasks. On the one hand, it provides for a frictionless liquid lubrication or gas cushion which also absorbs the pressure on the flat material, and on the other hand it cools the tape or the jacket from the inside in direct contact.

It is advantageous if the length of the contacting surface of a circulating belt or a rotating roll shell is at most 2000 mm, preferably at most 1000 mm. The structure of the cooling element simplifies constructively considerably. Technologically, the flat material experiences a type of short "pulse cooling" which has proven to be very advantageous in the overall cooling process. Assuming that the sheet material has a speed of 1.0 to 2.0 m / s, the cooling pulses last about 100 to 800 ms.

Preferably, a plurality of cooling elements are provided one behind the other with at least one temperature compensation zone lying between them.

It has been shown that it is possible with this arrangement in positive effect to cool the running flat material before or possibly even after cutting into desired Längenabschnit¬te very strong in the core. A goal that was achieved with this invention was to cool the sheet as a whole by at least 50 ° C.

The entire cooling section should not exceed 25 meters as possible. This secondary objective is fulfilled with the device according to the invention. As a rule, this is an inlet temperature of about ΙΟΟΌ to a temperature (preferably before the cut) of below 50 ° C, is desirable and achievable - depending on the thickness of the flat material - even below 40 ° C.

Under the temperature compensation zone is a stretch for the flat material to understand, in which the greatly reduced in the cooling element surface temperature and the core temperature approach each other again. In addition, a moisture and Dampfdruckausgleich take place.

Preferably, the temperature compensation zone has a length of 100 to 2000 mm. In this section, the sheet is given the opportunity to lower the temperature gradient from surface to core again. The internal heat is therefore carried out with the opportunity of a moisture and vapor pressure equalization to the outside. In contact with the next cooling element, the process is repeated until both surface and core temperatures are at an approximately equal and low level. Preferably, the temperature compensation zone is at least partially provided with a hood open towards the flat material. Thereby, a temperature compensation zone with a conditionable atmosphere near the surface of the sheet is created between the cooling elements. It can "flash" -like evaporations are avoided and thus tearing and roughening of the surface.

As in the temperature compensation zone can be additionally provided that umlaufenden bands encapsulated and / or conditioned. This prevents condensation on the cold strips.

Advantageously, it is ensured that at least 10 cooling elements are connected in series. From this number of cooling elements with a contact length of about 800 mm, it has surprisingly been possible to cool down medium-strength HDF boards from a core temperature of 100 * 0 to 50 °.

It is advantageous if the cooling elements on the opposite side of the plate is assigned in each case a counter element. This not only acts as a counterforce to the pressure built up by the cooling element against the flat material, but is suitably also designed as a cooling element. This results in a symmetrical temperature curve over the flat material thickness and the heat accumulated on the inside can flow off in two directions.

Preferably, the counter element and the cooling element are constructed largely identically. It is also advantageous if all cooling and counter elements are constructed substantially the same. This creates a module which, depending on the Fasermaterialbrei¬te only once must be constructed and finally, as needed, can be used several times in succession.

It is advantageous if the band or the sheath has a maximum wall thickness of 0.1 to 2 mm and at least the surface of the band or the jacket consists of Metall.Dadurch is the heat dissipation because of the high thermal conductivity of the sheath or Band¬ material facilitates. A 0.2 mm thick strip of electroformed nickel has proven to be particularly effective here.

In order to obtain a very smooth surface of the flat material, it is also advantageous if the surface of the band or of the shell has a roughness with a maximum

Value of 0.8 pm.

In many cases, it is advantageous if the flat material is "calibrated" before it reaches the first cooling element. For this purpose, it is provided that at least the first cooling element is preceded by a roller nip for the flat material. Such a nip is spielsweise in a calender. The rollers may be provided with adapted surfaces, such as hard and smooth metal to produce a particular smoothness, or with an elastic coating to achieve a uniform compaction. In addition, the rollers can be tempered.

With respect to the method, the object of the invention is achieved in that a cooling of at least 50 ° C via the device described.

And with respect to the product of a UTMDF or UTHDF plate having a thickness of 1 to 3 mm, the object of the invention is achieved by cooling it by means of the described device.

The invention will be explained in more detail below with reference to an embodiment with Bezugnah¬me to the drawings. 1 shows a schematic, partially sectioned illustration of an apparatus according to the invention for cooling, [0031] FIG. 2 shows a cross section through a cooling element, [0032] FIG. 3 shows a three-dimensional illustration of a cooling element without a strip and [0033] FIG 4 is a diagram in which the temperature profile of the core and surface of a

Flat material over the treatment time in the device according to the invention is shown.

The device 1 for cooling a flat material 2, in particular of (UT) MDF or (UT) HDF plates, shows in the web running direction first a calibrating nip 3 and then a plurality of successively connected cooling elements 4, each with a more than 100 mm long, circumferential contact surface 5 to the flat material 2, and their counter-elements 4 'on the opposite side of the sheet 2. The counter-elements 4' are constructed identically, as the cooling elements 4, so that the device be¬sitzt several similar modules. Both cooling element 4 and counter element 4 'have a frame 8 in which two deflection rollers 6 are mounted. In this case, the contact surface 5 is formed by a metal band 7 which circulates over the two deflection rollers 6. Alternatively, however, flexible roller coats would also be conceivable. Within the frame are refrigerated elements 9, in particular Andru¬ckelemente stored, which will be described later. Each cooling element 4 has at least one connection, not shown, for a cooling fluid. Via the cooling fluid, the metal band 7 is cooled on the side facing away from the flat material, that is to say on the inside. In this way, the heat is dissipated from the surface area of the fiber material through the metal band 7. For this purpose, the band has a very small thickness of, for example, 0.3 mm and is made of a good heat-conducting metal such as steel or better nickel. The temperature of the cooling fluid can be monitored, and as soon as the cooling fluid in the sealed cooling element 4 has exceeded a temperature limit, it is discharged via drain lines (not shown). In order to make the cooling device 1 according to the invention particularly effective, at least 10 cooling elements 4 should be connected in series (for illustrative reasons only four are shown in FIG. 1). In addition, if the metal strip 7 has a surface roughness Ra below 0.8 μm, even after-smoothening effects can be produced.

Between the cooling elements 4 temperature compensation zones 10 are provided. This is a path for the flat material 2, in which it is not actively cooled. When the sheet 2 is in the temperature compensation zone 10, heat flows from the hotter core to the recently cooled surfaces of the sheet 2. The temperature compensation zone 10 is covered by a hood 11 to provide a favorable, humid, ie conditioned, atmosphere. so that it does not come to Flashverdampfungen and thus to a roughening of the surface of the sheet 2. The temperature equalization zone 10 has a length of 100 to 2000 mm, in this embodiment about 900 mm. In addition, the temperature compensation zones prevent a condensation of ambient air on the flat material 2 or the band 7. Accordingly, in an unillustrated manner, each band 7 may also be at least partially enclosed.

The nip 3 is formed by two rollers 12, 13. The roller 12 is in this case a roller with a jacket 15 which can be bent over at least one support element 14 and can be turned against the roller 13. The flat material 2 is also pressurized via the at least one support element 14 and correspondingly smoothed or calibrated.

FIG. 2 shows a cross-section through a counter-element operating against each other and constructed identically. Between the two, the sheet 2 is cooled. Against the circulating metal band 7 presses the (pressure) element 9, which is supported on the frame 8. In the band 7 side facing the element 9 zones 16 are incorporated. These pocketed zones 16 are supplied with pressurized cooling fluid to build up a pressure pad between element 9 and belt 7. The contact pressure can therefore be generated via the pressure of the cooling fluid. In the area of the edges of the flat material 2, a plurality of narrow zones (pockets 16 ") are provided, while the zones (pockets 16 ') in the center of the sheets may be larger. The purpose is to be able to more accurately adjust the pressure and cooling to the often drier or thinner edges of the sheet 2 in order to subsequently obtain a uniform transverse profile of the sheet 2.

The spring 17 acts on the edge even in the opposite direction to the hydrostatic fluid pressure in the pockets to build in extreme cases, although a lubricating film, but to be able to completely exclude pressure on the edges of the sheet 2. In addition, with the aid of this configuration of a plurality of narrow pockets 16 "and the spring 17, which can be controlled individually with cooling fluid, the entire cooling element 4 is at different, d. H. adjustable Flachmaterialbrei¬ten adjustable. It has therefore been created by the pockets 16 ', 16 "different controllable zones 16, can be reacted to any cross-sectional deviation in the sheet.

In the figure 3, the cooling element 4 is shown in three dimensions. For a better understanding, the band 7 was not drawn. With this representation, the pocket distribution of the zones / pockets 16, 16 'and 16 "in the pressure element 9 is better illustrated.

The technological mode of operation of the device according to the invention can easily be demonstrated on the basis of the diagram in FIG. 4 with reference to a practical example. The temperature is applied over the cooling time. The curve A stands for the core temperature of the flat material 2 and the curve B shows the temperature profile at the surface.

At time T = 0, the sheet, in this case a UTHDF sheet having a thickness of 3 mm, runs at a continuous temperature of 100 ° onto the first cooling element 4. The surface is contacted by the strip 7, which has a thickness of 0.1 to 2 mm, abruptly cooled to about 30 ° C. The temperature of the cooling fluid (in this case water) is maintained at 15 * Ό.

Cooling elements 4 and temperature compensation zone 10 are designed so that they are traversed at a speed of 1.8 m / s each 500 ms. In total, sixteen cooling elements are connected in series. The total length of the device according to the invention is therefore about 28 meters.

After leaving the first cooling element, ie in the first Temperaturaus¬gleichszone, the surface temperature increases at the surface again up to 65 ° C. However, the core temperature decreases due to the heat flow. Shortly after all sixteen cooling elements have passed through, both the core and the surface temperature are in a field of 25 to 45 * 0 and finally evened out to 35 ° C. As a result, the flat material can be cut and stacked without cooling for cooling, without becoming wavy.

REFERENCE LIST 1 Apparatus for cooling 2 Sheet material 3 Nip 4 Cooling element 4 'Counter element 5 Contact surface 6 Deflection roller 7 Belt, metal belt 8 Frame 9 Element, pressure element 10 Temperature compensation zone 11 Hood 12 Roller, bendable 13 Counter roller 14 Support element 15 Sheath 16 Hydrostatic pockets, zones 16' Hydrostatic pockets in center of sheet, zone 116 "Hydrostatic pockets on sheet edge, zone 2 17 Spring A Temperature curve over time KernB Temperature curve over time Surface

Claims (13)

Claims 1. A device for cooling moving flat material (2) from a mixture of lignocellulosic and / or cellulose-containing particles, in particular HDF and UTHDF plates or MDF and UTMDF plates, preferably added with binding agent, following one hot, compacting production process, wherein the cooling via at least one circumferential, the flat material (2) in operation in the direction over a length of at least 100 mm contacting surface of a circulating belt (7) or a umlau¬fenden roll shell of a cooling element (4) vornehmbar is, wherein the peripheral belt (7) or the rotating roll shell beauf¬ charged on the inside with a cooling fluid and under a contact pressure against the flat material (2) can be pressed, characterized in that the contact pressure and / or the cooling capacity over several, At least one zone (16) arranged transversely to the running direction of the flat material and independently controllable Elementes (9) can be applied. Device according to claim 1, characterized in that the element (9) is a pressure element which presses the circulating belt (7) or the rotating roll shell against the flat material (2). A device according to claim 1 or 2, characterized in that the zones (16) are narrower in the area of the edge of the flat material transverse to the running direction of the flat material than in the middle. Device according to any one of Claims 1 to 3, characterized in that the zones (16) comprise hydrostatic pockets (16 ', 16 "). 5. Device according to one of claims 1 to 4, characterized in that the contact pressure on the pressure of the cooling fluid can be generated. 6. The device according to claim 1, characterized in that the length of the kontaktie¬renden surface (5) of a circulating belt (7) or a rotating roller shell is at most 2000 mm, preferably at most 1000 mm. 7. Device according to one of claims 1 to 6, characterized in that a plurality of cooling elements (4) are provided one behind the other with at least one Tempera¬turausgleichszone (10) located therebetween. 8. The device according to claim 7, characterized in that the Temperaturaus¬gleichszone (10) has a length of 100 to 2000 mm. 9. Device according to one of claims 7 to 8, characterized in that at least ten cooling elements (4) are connected in series. A device according to any one of claims 1 to 9, characterized in that a respective counter element (4 ') is associated with the cooling elements (4) on the side opposite the flat material (2). 11. The device according to claim 10, characterized in that the counter-element (4 ') and the cooling element (4) are constructed substantially identical. 12. Device according to one of claims 1 to 11, characterized in that the band (7) or the jacket has a wall thickness of at most 0.1 to 2 mm and zumin¬ the surface of the band (7) or of the shell consists of metal , 13. Device according to one of claims 1 to 12, characterized in that at least the first cooling element (4) a roller gap (3) for the flat material (2) is pre-switched. 4 sheets of drawings