DE20317931U1 - Air measurement unit,for applying plastic onto a cooling member, comprises a housing with one or more pressure lines, an air outlet slot, and a slot adjustment unit - Google Patents

Abstract

An air measurement unit, comprises a housing (3) with one or more pressure lines (7) that lead to the measurement unit (1), a longitudinal air outlet slot (31), and an edge adjustment unit (39) for altering the slot length. The housing contains an air equalisation chamber (5) which is connected to the pressure lines. An air measurement unit, comprises a housing (3) with one or more pressure lines (7) that lead to the measurement unit (1), a longitudinal air outlet slot (31), and an edge adjustment unit (39) for altering the slot length. The housing contains an air equalisation chamber (5) which is connected to the pressure lines. The measurement unit is a high pressure unit, and the slot width is less than 200mu m, especially 100mu m. The air outlet pressure can exceed 1 bar. The nozzle lip adjustment comprises a number of members which can be adjusted mechanically, electromechanically, electrochemically, pneumatically or hydraulically.

Description

The invention relates to an air knife for applying plastic film melts to a heat sink, in particular a chill roll according to the preamble of claim 1.

Especially in manufacturing of plastic films, for example films made from polymer melts, it’s common practice from a slot die emerging melt film using a so-called air knife Generation of a sufficient air speed (dynamic pressure) a chill roll to press. The air knife extends in its longitudinal extent across the width of the melt film, that is to say transversely to the withdrawal direction of the plastic film, being about a continuous exit slot (or a plurality closely spaced side-by-side exit openings) to generate a corresponding Air velocity Exit air in the direction of the melt film can.

In addition to generating an air pressure, what the Is pressed against the heat sink, it is alternative or supplementary also possible, generate a negative pressure between the roller and the melt plume is pressed onto the heat sink. Furthermore, as an alternative or in addition, it is also possible to use one Generate negative pressure between the roller and the plume generated in the so-called "gusset area" of the incident melt becomes. Finally but is also the application of the melt film by means of electrostatic At least surface forces supportive possible. When applying the melt plume to the heat sink, make sure that that one if possible good heat transfer between the polymer melt and the heat sink, especially without air pockets. Otherwise it would this leads to an uneven thickness distribution of the film to be produced. It would also come uneven heat transfer and thus an uneven crystallization the slide.

A generic air knife is for example from the DE 196 18 716 A1 known. It has a housing body with a central inner air supply chamber, via which the compressed air supplied can ultimately exit via an air outlet gap pointing in the direction of the film. Since the melt or cast film that emerges from a slot nozzle and is placed on a heat sink, usually a cooling roller, undergoes a so-called neck-in in its width, it is necessary, among other things, to make an edge adjustment or an edge adjustment for to provide the air knife. In this type of the known air knife, the film edges flutter due to the increased volume flow, which mainly flows laterally over the melt edge. The air knife must therefore be sealed off at the edge of the cast film. The effective length of the air knife known from the aforementioned publication can easily be adapted to the respective width of the cast film.

With one from the EP 0 051 699 B1 In the known device, an air knife is described which comprises a plurality of individual chambers which can be supplied with air separately. This makes it possible to adapt to the working width of the melt plume, ie the effective length of the air knife (transverse to the direction in which the film web is drawn off) can be adjusted. However, this single-chamber distribution, in particular its partition walls, has a negative effect on the pressure line distribution, in particular when the air knife is set at very short distances from the melt plume. Therefore, the knife arrangement known from the above-mentioned prior publication must be set to a comparatively large distance of approximately 3 to 6 mm from the cast film in order to improve the pressure line distribution by mixing the escaping compressed air. However, this means that the contact pressure drops further. From this prior publication it can also be seen that the slot width of the air knife is approximately 0.75 mm, the exit speeds being relatively low.

From FR 2 697 198 A1 is also an air knife with radial fans and side channel blowers as known. According to the US 2003/0 025 237 A1 describes an application method in which between a rough chill roll and an air layer is introduced into the melt film, the air knife as a control device for this Air cushion is used.

Especially when the working widths are due to larger film widths increase, this has several disadvantageous consequences, namely:

• - With increasing working width this to higher volume flows in the radial fans and side channel blowers.
• - With increasing width, this requires even higher requirements for air uniformity over the whole Working width.
• - Finally will the problem of avoiding friction losses and temperature increases increasingly difficult to implement in the supply lines.
• - Finally, due to the higher flow rates and the larger radial fans and side channel blowers usually also take additional measures to reduce the noise level carried out become.
• - In addition the mechanical effort increases in order to adjust the nozzles accordingly and hold.

The object of the present invention is to provide an air knife with which it is possible to apply a melt film or a melt web even better to a heat sink, in particular to a cooling roller. Thus, the goal of the registration is among other things the contact pressure on the To increase the melting plume or to influence the thickness profile of the pre-film.

The task will correspond to the invention solved the features specified in claim 1. Advantageous configurations the invention are specified in the subclaims.

In contrast to the state of the art a high pressure nozzle is used according to the invention, the in contrast to the air knives known from the prior art with working pressures that works over 1 bar and, for example, quite a magnitude of about 10 bar and achieve more.

It is further provided according to the invention that the slot nozzle width of the air knife arrangement is not approximately 300 to 400 [μm] as in the prior art as in the case of the EP 0 051 699 B1 described 750 [μm]), but is significantly less, for example 100 [μm] and less.

Through this configuration according to the invention so is it possible the contact pressure on a melt flag, i.e. a cast film opposite the stand technology to increase significantly, which also has a positive influence on the thickness profile of the pre-film and the further occurring in the prior art and explained above Disadvantages are avoided.

The nozzle according to the invention is preferred with a Provide swivel device. It has proven to be beneficial arrange the pivot point so that it is in the middle of the nozzle outlet comes to rest.

The high-pressure air knife according to the invention for Systems in particular of polymer melts is preferred over the working range of the Air knife equipped with high pressure feed lines, which is preferred individually over Throttles can be adjusted for air uniformity over the To ensure working width and thus to positively influence the thickness profile of the pre-film. Finally, as also provided in the prior art, an edge setting on the high-pressure air knife according to the invention provided to ensure that, in particular in the edge region of the Castfilmes can not take off the melt flag.

Other advantages, details and Features of the invention result from the explanations given below Embodiments. The following show in detail:

1 a schematic side view of an air knife arrangement according to the invention (transverse to the longitudinal direction of the air knife);

2 : a schematic direct view of a cast film and an air knife according to the invention, extending transversely above it, with a large number of high-pressure feed lines;

3 : A schematic cross-sectional view through the air knife according to the invention to explain an edge cover;

4 : A cross-sectional view through the air knife according to the invention with a schematic diagram for changing the outlet gap;

5 : a further modification of the air knife according to the invention in cross-sectional representation to improve the air discharge; and

6 : a supplement to the embodiment according to the 1 to 5 using two condensation traps.

The schematic representations according to 1 and 2 include an air knife assembly with an air knife 1 , which has an elongated housing, or an elongated air knife body 3 having.

Inside the air knife housing 3 is at least an air chamber 5 provided, which is designed in the manner of an integrated antechamber and is sometimes also referred to as a "lamination box". This integrated prechamber 5 serves to equalize the compressed air fed in over the entire length of the air knife.

As seen from the cross-section 2 can be seen lead a variety of pressure supply lines 7 to the air knife 1 , wherein in the embodiment shown all pressure supply lines 7 one choke each 9 is assigned to the via the pressure supply line 7 individually adjust or regulate the supplied air pressure. Although all feed lines 7 to a common integrated antechamber 5 in the air knife housing 3 can nevertheless be used to fine-tune the compressed air exiting through the air outlet gap of the air knife.

In 1 the preparation, preparation and supply of the compressed air is also shown schematically. The entire facility includes a compressor 13 , which can be driven for example by a motor (for example with an electric motor) and compresses the air supplied and a pressure vessel 15 (Pressure chamber) feeds. The compressed air treatment is basically designed so that completely oil, water and / or particle-free air is used. This is also necessary to prevent the slot nozzle from becoming clogged with the narrow slot widths.

Via one from the pressure vessel 15 or the pressure connection line between the compressor 13 and pressure vessel 15 branching and ultimately to the supply lines 7 leading pressure line 17 can, for example, a first preferably adjustable or adjustable throttle 19 , one or more subsequent further also adjustable or controllable chokes 9 and an intermediate pressure and / or flow meter 23 be connected (for example via a pressure branch line 17 ' ), whose measurement data is ultimately a regulation 27 are feedable, via which the mentioned, the individual feed lines 7 upstream chokes 9 are controllable. In the embodiment shown 1 is between the first throttle arrangement 19 and the second Dros selanordnung 9 yet another pressure chamber 16 shown with a so-called laminate chamber, which serves to optimize the pressure distribution.

In the presentation according to 1 is just a throttle 9 shown, which is then via a subsequent feed line 7 the integrated antechamber 5 the air knife 1 assigned. However, the pressure line is preferred 17 via a distributor with a large number of pressure lines connected in parallel 7 connected, each with an adjustable or adjustable throttle 9 is provided like this from 2 can be seen. In other words, the throttle supply lines shown there can 7 ' via a manifold with a single pressure line 17 be connected.

The number of chokes and / or additional pressure chambers can vary in a wide range, so instead of only one additional pressure chamber also two, three, four further pressure chambers etc. or additional ones Pressure and / or flow measuring devices at different points can be provided.

By the mentioned pressure and / or flow measuring devices as well the one above Controlled throttling or flow devices can ultimately be a Optimization of the contact pressure and immediate regulation of the thick profile of the plastic film to be produced and processed over the entire working width.

How out 1 and 2 you can also see the air knife 1 transversely, ie in particular perpendicular to the direction in which a cast film is drawn 29 , which is also sometimes referred to below as the melt plume, at a short distance above the melt plume 29 arranged. At the bottom of the air knife is the air outlet nozzle already mentioned 31 provided, which is formed in the form of a narrow slot nozzle, which is aligned in the direction of the melt plume. The melt plume is usually placed on a chill roll 33 created, which is in the pull-off direction of the film according to the arrow representation 35 turns, being on the jetty 37 the air knife 1 is arranged and aligned so that the air stream emerging through the outlet gap the cast film 29 as far as possible without air pockets on the surface of the chill roll 33 pressed and applied.

Ultimately, regarding the out 2 If the polymer melt appears to have entered (neck-in), the effective length of the air knife must be adjusted accordingly (that is, based on the corresponding effective width of the cast film), it is necessary to use an appropriate edge adjustment device 39 provided. Without such an edge adjustment device, the melt plume would be lifted off the chill roll due to the Bernoulli effect. The edge adjustment can also be correlated with the pulling or pulling speed. Preferably, a motorized adjustment of the edge cover is also carried out, so that a corresponding control, in particular also automatic control and / or controllable changes, can be carried out at any time as required.

According to the schematic cross-sectional representation according to 3 can the edge adjustment device 39 by using an edge cover 39a be formed, for example, on the to the feed lines 7 opposite boundary wall 3a of the air knife body 3 in the outer end area of the housing 3 of the air knife 1 (i.e. in the area of the film edge 29 ' ) provided and anchored, but in the longitudinal direction of the air knife 1 is slidable, this edge cover 44 according to the cross-sectional representation 3 the lower air outlet gap 31 completely covered and closes. Depending on the axial adjustment according to the arrow representations 43 in 2 can now this edge cover 39a are pushed more outwards or further inwards, which means that an adjustment can now be made to the extent that air under high pressure is above the air outlet gap 31 is squeezed. The edge cover mentioned 44 and thus the axial lengthening or shortening of the effective air outlet gap 31 depending on the jump-in, which also depends on the take-off speed of the cast film, either manually or via a control 27 tracked to ultimately lift off the melt plume 29 to prevent from the surface of the chill roll.

The desired pressure line profile along the working width is determined via the individual supply elements, ie usually the chokes mentioned 9 set. This allows the application force to be optimized across the working width.

Because of the narrow slot width for example less than 200 μ (0.2 mm) and less, for example on the order of magnitude of only 100 μ or even only 50 μ and less attention is also paid to the compressed air supply particle and thus dirt-free.

In general it can be noted that the slot width have any value below 200 μ can, up to values of, for example, 10 μ and less.

The escaping air flow is there suppress from above 1 bar, i.e. it can have values of, for example, up to 10 or even Reach 15 bar and more.

In order to influence the application force over the working width of the air knife and thus also the thickness profile of a plastic film to be produced, it is not only a matter of changing the air pressure and / or the air quantity supplied via the throttles mentioned 9 possible, but for example also via an optionally provided nozzle lip adjustment 45 ( 4 ). The nozzle lips 47 limit the air outlet gap between them 31 , According to the schematic representation 4 is at least a Dü senlippe 47a via the nozzle lip adjustment device mentioned 45 adjustable, namely essentially transversely to the plane of the air outlet gap 31 , so that the width of the air outlet gap 31 is changeable. The nozzle lip mentioned at first can 47a for example, directly or via a lever adjustment 45a (In the embodiment shown, a rocker arm 45b and two at the opposite ends of the rocker arm 45b attacking adjustment lever 45c and 45d ) via one or more actuators 49 differently adjusted and thereby optimized. The actuators can be actuated mechanically, electromechanically, electrochemically, pneumatically, hydraulically or in any other way. The actuators are attached to one 50 supported accordingly and can be operated (if necessary even manually).

A plurality of actuators is again preferably offset from one another along the longitudinal direction of the air knife, so that the width of the air outlet gap 31 over the length of the air knife 1 can even be set differently in order to optimize the application force across the entire working width. In the embodiment shown, the rocker arm is 45b on a rocker support 46 pivoted, the rocker support 46 in the embodiment shown on the air knife body 3 is anchored. The actuator attachment is either located directly on the nozzle body (air knife 1 ) or for example on a separate carrier. It is also a nozzle lip adjustment device ( 45 ) is provided, above which the air outlet gap ( 31 ) is adjustable in its width, preferably with correlation with the take-off speed.

Often the nozzle lip adjustment of the melting nozzle, from which the cast film 49a escapes, due to the viscoelastic behavior of the melt, which also causes the so-called entry (neck-in) after the melting nozzle is not sufficient to influence the ceiling profile completely in the desired sense, can be done by the mentioned nozzle lip adjustment on the air knife 1 cause this additional readjustment to optimize the film to be produced.

The lower volume flows compared to conventional solutions with a simultaneous significant increase in the contact pressure also contribute to the fact that the dramatic flutter of the melt plume, which occurs in the prior art, is reduced by the deflected air flows. The high-pressure air knife explained 1 adjusted at a short distance from the film. In addition, since the air knife according to the invention only requires a small installation space in its transverse direction, this also contributes to the fact that the free path length of the melt plume 29 after leaving the in 1 melting nozzle, not shown, can be kept short until it hits the cooling roller. This also counteracts a possible flutter of the cast film. Finally, there is also an angle adjustment for the air knife 1 provided, the axis of rotation (as shown in the enlarged detail cross-sectional view 5 can be seen) is in the center of the nozzle outlet. This in turn also helps to ensure that the air outlet nozzle 31 escaping and then deflected air currents affect the melt plume only slightly.

A further improvement can also be achieved in that according to the schematic cross-sectional representation of FIG 5 additional baffles 51 are used, which are preferably in the pull-off direction in front of and behind the air knife transversely to the plastic film web immediately adjacent to the air knife or to the air knife body 3 are arranged and with their baffle edge closest to the cast film 51a approximately at the level of the exit gap 31 at the bottom of the nozzle lips 47 end offset to the side. Will be in the area V between the baffles 51 and the adjacent side of the housing 3 of the air knife 1 generates a negative pressure, so the deflected air flows can according to the arrow 53 over the between the baffles 51 and the adjacent boundary of the nozzle lip 47 formed way are led away.

Alternatively or in addition, you can use the nozzle lips 47 still mantle flow holes 55 be introduced, preferably over the entire length of the air knife 1 , The jacket flow holes serve to reduce noise.

In air knives of the prior art, the required high volume flows in connection with the big one Design that the air flow in the narrow space between the nozzle and roller cannot be removed quickly enough, which is why the melt plume is fluttered.

The high pressure nozzles generate due to Bernoulli a mantle flow, which are essential for noise reduction contributes. This effect can be achieved through the mentioned Installation of jacket flow holes and baffles can also be further improved. With nozzles of the State of the art leads the high volume flow in connection with the wide nozzle slots to a considerable noise pollution.

As for the narrow nozzle slots particle-free air is used, and modern air filtration in compressors by means of condensation, there is cold, and oil free Compressed air available, which in connection with the Joule Thompson effect also for an additional cooling the applied melt surface, and thus the crystallization improved.

Because a strong evaporation of volatile Be Components can be observed, which are used to fog up the outer surfaces of the air knife 1 and especially the areas around the nozzle lips 47 are condensation traps 59 intended. As shown in the schematic cross-sectional representation 6 It can be seen that these condensation drops consist, for example, of two pipes or lines arranged parallel to the air knife, which are preferably at the level of the nozzle lip 47 are arranged, ie at least one line or pipe 59a in the trigger direction in front of the nozzle lip 47 and another pipe or line 59b in the withdrawal direction of the cast film 29 after the nozzle lip 47 , This line 59a and 59b are preferably flowed through with cooling water or cooling air. This contributes to the condensate now trapping on these condensation traps 59 reflected. This condensation arrangement can then be cleaned more easily than the entire air knife during the cleaning intervals.

Claims (19)

Air knife arrangement, in particular for applying plastic films to a heat sink such as a cooling roller, with the following features: the air knife comprises a housing or an air knife body ( 3 ), - with one or more to the air knife ( 1 ) leading pressure supply lines ( 7 ), - with one in the longitudinal direction of the air knife ( 1 ) extending air outlet gap ( 31 ), - with an edge adjustment device ( 39 ), about which the effective length of the air outlet gap ( 31 ) is adjustable or changeable, - with at least one in the housing or in the air knife body ( 3 ) integrated air compensation chamber ( 5 ) which, on the one hand, at least indirectly with the one or more pressure supply lines ( 7 ) and the other with the air outlet gap ( 31 ) is characterized by the following additional features: - the air knife ( 1 ) consists of a high-pressure air knife, - the slot width of the air outlet gap ( 31 ) is less than 200 μ, in particular less than 100 μ, and - a pressure generating and / or pressure supply device is provided, via which an air outlet pressure at the air outlet gap ( 31 ) of over 1 bar can be generated. Air knife arrangement according to claim 1, characterized in that the air outlet gap ( 31 ) has a width of 10 μ to 160 μ, in particular between 20 μ to 80 μ. Air knife arrangement according to claim 1 or 2, characterized in that the air outlet gap ( 31 ) has a width of 40 μ to 60 μ. Air knife arrangement according to one of claims 1 to 3, characterized in that a nozzle lip adjustment device ( 45 ) is provided, above which the air outlet gap ( 31 ) is adjustable in its width, preferably with correlation with the take-off speed. Air knife arrangement according to claim 4, characterized in that the nozzle lip adjustment device ( 45 ) over the longitudinal direction of the air knife several actuators arranged offset to each other ( 49 ), which can preferably be actuated or controlled separately, via which the air outlet gap ( 31 ) on in the longitudinal direction of the air knife ( 1 ) Staggered positions can be set differently. Air knife arrangement according to claim 4 or 5, characterized in that the actuators ( 49 ) can be adjusted or adjusted mechanically, electromechanically, electrochemically, pneumatically, hydraulically or the like. Air knife arrangement according to one of claims 4 to 6, characterized in that the actuators ( 99 ) via a control device ( 27 ) can be controlled automatically. Air knife arrangement according to one of claims 4 to 7, characterized in that the nozzle lip setting ( 45 ) is constructed in such a way that at least one of the two has the air outlet gap ( 31 ) forming nozzle lips ( 47a ) transversely to the opposite nozzle lip with enlargement or reduction of the air outlet gap ( 31 ) is adjustable. Air knife arrangement according to one of claims 4 to 8, characterized in that the actuator ( 49 ) via a lever and / or rocker linkage ( 45a-45e . 46 ) with the at least one adjustable nozzle lip ( 47a ) connected is. Air knife arrangement according to one of claims 3 to 10, characterized in that the at least one or preferably a plurality of actuators ( 49 ) on the housing or on the air knife body ( 3 ) or a separate carrier ( 49a ) are anchored and / or held. Air knife arrangement according to one of claims 1 to 10, characterized in that at least one condensation trap ( 59 ) is provided. Air knife arrangement according to claim 11, characterized in that the condensation trap ( 59 ) consists of a heat sink, which on at at least one or preferably on at least two opposite longitudinal sides of the air knife runs in the longitudinal direction thereof. Air knife arrangement according to claim 11 or 12, characterized in that the condensation trap ( 59 ) consist of lines or pipes through which coolant can flow. Air knife arrangement according to one of claims 1 to 13, characterized in that an edge adjustment device ( 39 ) is provided, about which the effective length of the air outlet gap ( 31 ) is adjustable. Air knife arrangement according to claim 14, characterized in that the edge adjustment device ( 39 ) an edge cover ( 39a ) which extends in the axial or longitudinal direction of the air knife ( 1 ) is adjustable so that the air outlet gap ( 31 ) in the longitudinally opposite end areas of the air knife ( 1 ) can be covered and locked in different ways. Air knife arrangement according to one of claims 1 to 15, characterized in that a pressure control device ( 27 ) is provided, via which the pressure of the air knife ( 1 ) through a variety of chokes ( 7 ) supplied air is adjustable over the working width of the air knife. Air knife arrangement according to one of claims 1 to 16, characterized in that a control device is provided, via which the nozzle outlet gap ( 31 ) adjustable over the working width of the air knife, preferably differently adjustable over the working width of the air knife. Air knife arrangement according to one of claims 1 to 17, characterized in that the thickness profile of the cast film (via the different control of the air volume and / or air pressure to be supplied over the working width of the air knife and / or via the control of the slot width of the air knife) 29 ) can be changed or variably adjusted across the working width. Air knife arrangement according to one of claims 1 to 18, characterized in that the regulation with respect to the cast film thickness profile over the working width of the cast film ( 29 ) and / or the working width of the air knife as a function of a thickness profile measurement that can be carried out by means of a thickness profile measuring device.