DE202011110528U1 - Device for cooling moving flat material - Google Patents

Abstract

Device for cooling moving flat material (2) from a mixture of lignocellulosic and / or cellulosic particles preferably mixed with binder, in particular HDF and UTHDF boards, or MDF and UTMDF boards, following a hot, compacting manufacturing process Cooling can be carried out via at least one circumferential surface of a circumferential belt (7) or a circumferential roller shell of a cooling element (4) which contacts the flat material (2) in operation in the running direction over a length of at least 100 mm, the circumferential belt ( 7) or the circumferential roller jacket can be acted upon on the inside with a cooling fluid and can be pressed against the flat material (2) under a contact pressure, characterized in that the contact pressure and / or the cooling capacity can be controlled via several, arranged transversely to the running direction of the flat material and independently of one another Zones (16) at least one element (9) open are acceptable.

Description

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

The production of HDF and UTHDF or MDF and UTMDF plates takes place in a hot compacting process. MDF stands for a medium density fiberboard or medium density fiberboard, while HDF refers to the high density fiberboard. More particularly, 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 of the thickness marking comes the intent in the name, the UT, to bear, the "Ultra Thin" characterizes. The desired production speed should reach up to 2 m / s.

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

From the DE 199 19 822 A1 and the DE 199 26 155 A1 Double-belt cooling presses are known, can be subjected to a about 15 mm thick material plate of a shock cooling. From both publications is removable (particularly detailed in the 2 of the DE 199 126 155 A1 ) that core temperatures of 80 to 100 ° C can be achieved. It is known that material panels after such a treatment often have to be stored in such a double-belt cooling press usually for a long period of time in so-called "cooling stars" until they have reached a temperature at which they are stackable. Or the panels must be ground in similar systems because the surfaces are roughened.

Particularly serious - and especially with thin sheet material according to the invention - is when it comes to density or thickness variations in the transverse profile in the production process. With UTMDF / UTHDF flat material, the unevenness can arise due to fluctuations in the scattering, ie they are variations in basis weight. These are even in modern systems in the order of 10 kg / m ³ at a mean plate density of 860 kg / m ³ . It would be unavoidable when using the last-mentioned double-belt cold press alone that the (UT) MDF or (UT) HDF plates become wavy when stacked sections are cut. If the stacking takes place, if the temperature of the flat material is still too high or has a too high 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 reworked, which consumes a not insignificant production time.

The object of the invention is therefore to provide a device with which a flat material according to the invention can be cooled without significant loss of quality such that it can be produced faster and more accurately than the state of the art permits.

The object is achieved according to the device in that the contact pressure and / or the cooling power can be applied via a plurality of zones of at least one element which are arranged transversely to the running direction of the flat material and can be controlled independently of one another.

The cooled strip or jacket has 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 marginal zones of the sheet at different pressures or temperatures than that applied in the center of the sheet. 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. In the case of MDF / HDF flat material, the unevenness, as stated, could be caused by fluctuations in the scattering, ie they are variations in basis weight. These are even in modern systems in the order of 10 kg / m ³ with a mean plate density of 860 kg / m ³ . The printing in each zone can in this case, for example, are controlled via a processor using the thickness differences determined by a sensor.

It is advantageous if the element is a pressure element which presses the circulating belt or the rotating roll shell against the flat material. One thus possesses an element which is suitable for applying the base pressure to the tape or the jacket. Over the zones then only the local pressure increases or cooling performance changes must be effected. Preferably, the pressure element is provided within the cooling element 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 friction coefficients.

Preferably, the zones are narrower in the region of the flat material edge transversely to the running direction of the flat material than in the middle. This gives a finer Profilierungsmöglichkeit the edge, where usually the largest deviations from the nominal profile occur. In addition, there is the possibility of being able to treat 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 can be used to simply build up a pressure which, in the case of two relatively moving parts (band or jacket to the element), greatly reduces the friction. On the other hand, the hydrostatic fluid can also be used for cooling.

It is particularly preferred to ensure that the contact pressure can be generated via the pressure of the cooling fluid. For example, pressure elements are used which can be employed 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 in a so-called pressure pocket, which is embedded on the tape or the jacket facing surface of the pressure element. 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 fluid lubrication or gas cushion, which also absorbs the pressure on the sheet, and on the other hand, it cools in direct contact the tape or the jacket from the inside.

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 kind of short "pulse cooling", which has proven to be very beneficial to the overall cooling process. Provided that the sheet material has a speed of 1.0 to 2.0 m / s, the cooling pulses correspondingly last about 100 to 800 ms.

Preferably, a plurality of cooling elements are provided in series with at least one intermediate temperature compensation zone.

It has been shown that it is possible with this arrangement in positive effect to cool the current sheet material before or possibly even after cutting into desired lengths 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 far as possible. This sibling goal is met with the device according to the invention. As a rule, this is an inlet temperature of about 100 ° C to a temperature (preferably before the cut) of below 50 ° C, is desirable and achievable - depending on the thickness of the sheet even below 40 ° C. The temperature equalization zone is to be understood as a stretched section for the flat material, in which the surface temperature which is greatly reduced in the cooling element and the core temperature approach each other again. In addition, a moisture and vapor pressure equalization can 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 thus led out with the opportunity of a moisture and vapor pressure equalization. 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. This creates between the cooling elements a temperature compensation zones with a conditionable atmosphere near the surface of the sheet. It can "flash" -like evaporations are avoided and thus tearing and roughening of the surface. As in the temperature compensation zone, it can additionally be provided that encircling belts are 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 is surprisingly successful, moderate medium HDF plates already from a core temperature of 100 ° C to 50 ° C down.

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 also suitably designed as a cooling element. This results in a symmetrical temperature profile over the sheet thickness and the heat accumulated inside can flow off in two directions.

Preferably, the counter element and the cooling element are constructed largely identical. It is also advantageous if all cooling and counter elements are constructed substantially the same. This creates a module that has to be constructed only once depending on the fiber material width and finally, depending on requirements, can be used several times in succession.

It is favorable if the band or the jacket has a wall thickness of at most 0.1 to 2 mm and at least the surface of the band or the jacket consists of metal. As a result, the heat dissipation is facilitated because of the high thermal conductivity of the sheath or strip material. 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 sheet, it is also advantageous if the surface of the band or the shell has a roughness with a maximum Ra value of 0.8 microns.

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 nip for the flat material. Such a nip is for example 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 compression. 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 takes place 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 reference to the drawings. In this show

1 a schematic, partially sectioned view of a device according to the invention for cooling,

2 a cross section through a cooling element,

3 a three-dimensional representation of a cooling element without tape and

4 a diagram in which the temperature profile of the core and surface of a flat material over the treatment time is shown in the device according to the invention.

The device 1 for cooling a sheet 2 , in particular of (UT) MDF or (UT) HDF boards, first shows a calibrating nip in the web running direction 3 and then a plurality of cooling elements connected in series 4 each with a more than 100 mm long, circumferential contact surface 5 to the flat material 2 , and their counterparts 4 ' on the opposite side of the sheet 2 , The counter elements 4 ' are identical, like the cooling elements 4 so that the device has several similar modules. Both cooling element 4 as well as counter element 4 ' own a frame 8th in the two guide rollers 6 are stored. The contact surface 5 is in this case by a via the two guide rollers 6 circumferential metal band 7 educated. Alternatively, however, flexible roll shells would be conceivable. Inside the frame are refrigerated elements 9 , In particular pressure elements, stored, which will be described later. Each cooling element 4 has at least one, not shown, connection for a cooling fluid. About the cooling fluid is the metal band 7 on the flat material facing away, so cooled the inside. In this way, the heat from the surface area of the fiber material through the metal strip 7 derived through. 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 derived via drain lines, not shown. To the cooling device according to the invention 1 should be particularly effective, should have at least 10 cooling elements 4 be consecutive (for representational reasons are in 1 only four shown). Unless the metal band 7 also one Surface roughness Ra has less than 0.8 microns, even after-smoothening effects can be generated.

Between the cooling elements 4 are temperature compensation zones 10 intended. This is a path for the flat material 2 in which it is not actively cooled. When the flat material 2 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 from a hood 11 To create a favorable, humid, so conditioned atmosphere, so it does not cause flash evaporation and thus roughening the surface of the sheet 2 comes. The temperature compensation zone 10 has a length of 100 to 2000 mm, in this embodiment about 900 mm. In addition, the temperature compensation zones prevent condensation of ambient air on the sheet 2 or the band 7 , Accordingly, in a manner not shown, each band 7 be at least partially enclosed.

The nip 3 is through two rollers 12 . 13 educated. The roller 12 is a roller with a via at least one support element 14 bendable and against the counter roll 13 adjustable coat 15 , About the at least one support element 14 becomes the flat material 2 also pressurized and correspondingly smoothed or calibrated.

In the 2 is a cross section through each set against each other working cooling and identical counter element. Between the two is the flat material 2 cooled. Against the revolving metal band 7 presses the (pressure) element 9 that is on the frame 8th supported. In the band 7 facing side of the element 9 are zones 16 brought in. These trained as pockets zones 16 are supplied with pressurized cooling fluid, leaving a pressure cushion between element 9 and band 7 builds. 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 are several narrow zones (pockets 16 '' ), while the zones (pockets 16 ' ) may be larger in the middle of the sheet. The point is that you have pressure and cooling on the often drier or thinner edges of the sheet 2 can set more accurate, then to a uniform cross-sectional profile of the sheet 2 to obtain.

The feather 17 acts on the edge even in the opposite direction to the hydrostatic fluid pressure in the pockets, in the extreme case, although build up a lubricating film, but pressure on the edges of the sheet 2 completely ruled out. In addition, with the help of this design of several, individually controllable with cooling fluid narrow pockets 16 '' and the spring 17 the entire cooling element 4 adjustable to different, ie varying flat material widths. It is therefore through the pockets 16 ' . 16 '' different controllable zones 16 has been created, can be reacted to any cross-sectional deviation in the sheet.

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

The technological operation of the device according to the invention can be with reference to the diagram in the 4 easily show with reference to a practical example. The temperature is plotted over the cooling time. The curve A stands for the core temperature of the sheet 2 and the curve B shows the temperature profile at the surface.

At time T = 0, the flat material, in this case a UTHDF sheet with a thickness of 3 mm, runs at a continuous temperature of 100 ° C. onto the first cooling element 4 on. The surface is made by the contact with the tape 7 , which should have 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 ° C.

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 temperature compensation zone, the surface temperature at the surface rises again up to 65 ° C. However, the core temperature drops 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 ° C and finally equalized to 35 ° C. This allows the sheet to be cut and stacked without cooling for cooling without being wavy.

LIST OF REFERENCE NUMBERS

1

Device for cooling

2

flat material

3

nip

4

cooling element

4 '

counter-element

5

contact area

6

deflecting

7

Ribbon, metal band

8th

frame

9

Element, pressure element

10

Temperature equalization zone

11

Hood

12

Roller, bendable

13

backing roll

14

support element

15

coat

16

Hydrostatic pockets, zones

16 '

Hydrostatic pockets in middle of sheet, zone 1

16 ''

Hydrostatic pockets on the edge of the sheet, zone 2

17

feather

A

Temperature curve over time core

B

Temperature curve over time surface

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 19919822 A1 [0004]
• DE 19926155 A1 [0004]
• DE 199126155 A1 [0004]

Claims (13)

Apparatus for cooling moving material ( 2 ) from a mixture of preferably lignocellulosic and / or cellulosic particles, in particular HDF and UTHDF plates, or MDF and UTMDF plates, preferably added with a binder, following a hot, compacting production process, wherein the cooling takes place via at least one peripheral , the flat material ( 2 ) in operation in the running direction over a length of at least 100 mm contacting surface of a circulating belt ( 7 ) or a circumferential roll jacket of a cooling element ( 4 ) is vornehmbar, wherein the circulating band ( 7 ) or the circumferential roll shell on the inside can be acted upon with a cooling fluid and under a contact pressure against the flat material ( 2 ) is pressed, characterized in that the contact pressure and / or the cooling power over a plurality of transversely to the direction of the sheet material arranged and independently controllable zones ( 16 ) at least one element ( 9 ) are applicable. Device according to claim 1, characterized in that the element ( 9 ) is a pressure element that the circulating belt ( 7 ) or the rotating roll shell against the flat material ( 2 ) presses. Device according to claim 1 or 2, characterized in that the zones ( 16 ) are narrower in the region of the flat material edge transverse to the running direction of the flat material than in the middle Device according to one of claims 1 to 3, characterized in that the zones ( 16 ) hydrostatic pockets ( 16 ' . 16 '' ). 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. Device according to claim 1, characterized in that the length of the contacting surface ( 5 ) of a circulating band ( 7 ) or a circumferential roll mantle is at most 2000 mm, preferably at most 1000 mm. Device according to one of claims 1 to 6, characterized in that a plurality of cooling elements ( 4 ) in series with at least one intermediate temperature compensation zone ( 10 ) are provided. Device according to claim 7, characterized in that the temperature equalization zone ( 10 ) has a length of 100 to 2000 mm. Device according to one of claims 7 to 8, characterized in that at least 10 cooling elements ( 4 ) are connected in series. Device according to one of claims 1 to 9, characterized in that the cooling elements ( 4 ) on the flat material ( 2 ) opposite side in each case a counter element ( 4 ' ) assigned. Device according to claim 10, characterized in that the counter element ( 4 ' ) and the cooling element ( 4 ) are constructed substantially identical. Device according to one of claims 1 to 11, characterized in that the band ( 7 ) or the sheath has a maximum wall thickness of 0.1 to 2 mm and at least the surface of the strip ( 7 ) or the shell is made of metal. Device according to one of claims 1 to 12, characterized in that at least the first cooling element ( 4 ) a nip ( 3 ) for the flat material ( 2 ) is connected upstream.

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