Nozzle box as well as a stretching unit comprising a corresponding nozzle box

Abstract

ABSTRACT NOZZLE BOX AS WELL AS A STRETCHING UNIT COMPRISING A CORRESPONDING NOZZLE BOX An improved nozzle box comprises, among other things, the following features: - side walls (3b) spaced apart from each other, a base (3a) and a ventilation wall (5) spaced apart from it, thereby forming an interior space (2), - a plurality of ventilation openings arranged offset to each other is provided in the ventilation wall (5), - the nozzle box (1) is provided on its ventilation wall (5) with a plurality of protrusions (13) that are raised by at least a height (H) in relation to the sections of ventilation wall (5) or the top side or surface (5a) of the ventilation wall (5), said sections being located adjacent to the protrusions (13), - the ventilation openings (7) are configured raised in the region of the protrusions (13) in relation to the top side or surface (5a) of the ventilation wall (5) and / or the ventilation wall (5) comprises in the transverse direction (Q) of the nozzle box (1) opposing side flanges (19a, 19b) that overlap the side walls (3b) of the nozzle box (1) outside the interior space (2) of the nozzle box (1).

Description

The invention relates to a nozzle box according to thebroader term of claim 1 as well as stretching unitcomprising a corresponding nozzle box.Such nozzle boxes are used, for example, for heating andcooling web-shaped materials, in particular in the formof plastics films in the production of plastics films.Such a nozzle box serving as ventilation nozzle istypically arranged transversely, i.e. usuallyperpendicular to the drawing direction of the materialweb and thus transverse to the web travel directionabove and / or below the material web.Thus, for example, two or more such nozzle boxes can beassembled together to a ventilation field above as wellas below a material web, namely under the configurationof what is termed a ventilation module. Theseventilation modules including the corresponding nozzleboxes can then comprise, for example, a length extendingtransverse across the material web of up to 1.5 m, 3 m,5 m, 7.5 m or, for example, also up to 10 m and more.Depending on the application, the air and thus theplastics film can be heated via these ventilationmodules, for example in a preheating zone of astretching unit. To this end, the air is usually warmedand heated up via a heating system / heating unit. If theventilation module is deployed in a cooling zone, thefilm can also be cooled via correspondingly cooled air.In this case, the ambient air is drawn in and blown ontothe film. It is also possible that the air is cooled inadvance or that an air mixture comprising ambient airand hot air is used. In the recirculation mode, colderair (in comparison to the temperature of the film) isoften blown onto the film.The ventilation modules can be constructed to be closed(recirculation systems) or to be open (ambient air isused). In the case of heating material webs or inparticular plastics films, a closed ventilation systemis commonly used which blows air into the nozzle boxinterior spaces via ventilators arranged on the sides.From here, the air is then blown out in the direction ofthe material web / plastics film via outlet openings ornozzle openings in the nozzle boxes. Above and below thenozzle boxes, the blown air can flow back between theseboxes. In addition, for example, what are termed returnboxes are provided above or below the nozzle boxes, oreven just a free space, in order to draw back the airblown out there and then to heat it in the closed systemonce more and to supply it again to the nozzle boxes viathe ventilators. Heat exchangers can be used, forexample, for this heating. In this recirculation mode,the air can also be circulated several times.The aforementioned ventilation module comprising thenozzle boxes can be used in a preferred embodiment ofthe invention in transverse direction orienters ortransverse stretching ovens, in particular forsequential film-stretching units or in simultaneousfilm-stretching units.A nozzle box suitable for the described purposes isknown, for example, from EP 0 907 476 B1. The nozzle boxknown here comprises several interconnected air-supplychambers in its interior that extend in the longitudinaldirection of the nozzle box. The nozzle box itselfcomprises a ventilation or nozzle wall or side, in whicha plurality of ventilation openings, thus outletopenings or outlets, are usually configured for blowingout air. Often, a plurality of hole-shaped ventilationopenings is configured in several parallel rows arrangedside by side. To this end, the nozzle boxes are usuallyassembled above and below the material web in astretching unit in such a way that what is referred toas the ventilation or nozzle wall is aligned facing thematerial web. The design of the outlet openings oroutlets itself can be configured differently so thatboth hole-shaped as well as, for example, nozzle boxeswith slit-shaped outlet openings are possible.The air nozzle device is also known from CN 106003679 B.A plurality of outlet openings that can be provided in aspecific arrangement pattern are configured on thenozzle outlet side of a nozzle wall. To achieve certaineffects, cylinder-shaped protrusions are provided on theinner side of nozzles (thus on the inner side situatedopposite the outlet side of the nozzles), therebyincreasing the length of the nozzles.For completeness, it is also mentioned that above all inthe case of long nozzle boxes that these comprise or cancomprise at least two or more parts due to productionreasons which are assembled together in the longitudinaldirection for use in a stretching unit.In particular in the manufacture and stretching ofplastics films that are to be used as battery separatorfilms (thus in particular in what is termed a WETprocess), a range of admixtures and in doing so inparticular oil are admixed to the material of theplastics film to be stretched, said oil which in turnescapes and exudes from the material of the movingmaterial web when the film passes through an oven duringthe stretching process. This results in the exuding oilbeing deposited in the region of the ventilation wall ofthe nozzle box, in particular in the nozzle boxespositioned below the moving plastics film. From there,the exuded oil can then even enter the interior of thenozzle channel via the outlets.The penetration of the oil is however not limited to theoutlets. Oil can enter into the interior of the nozzlebox via any conceivable openings, recesses or slits,thus for example also via the sites of the flanges,interconnecting points of sheets etc.This then results in the oil that ultimately reaches theinterior of the nozzle box being taken and blown out inpart again by the recirculated air during operation withthe result that this oil reaches the surface of theplastics film to be stretched and leads to an unwantedimpairment in the quality of the plastics film to beproduced, i.e. to be stretched.It is therefore the object of the present invention tocreate an improved nozzle box, in particular for aventilation module as well as a stretching unit withsuch a nozzle box.The object is solved with regard to the ventilationmodule by means of a nozzle box with the features ofclaim 1 and with regard to the stretching unit with thefeatures according to claim 13. Advantageous embodimentsof the design are indicated in the dependent claims.The solution according to the invention is primarilycharacterized by the fact that the use of simplemeasures can prevent oil from entering the region of thenozzle openings and via these into the interior of thenozzle box. Therefore, it also prevents the gaseousprocess medium exiting through the nozzle openings(usually in the form of air) from swirling up oildeposited in the interior of the nozzle box or oildroplets found there and from bringing this oil towardsthe film, thereby preventing an unwanted depositing ofthis oil contamination on the plastics film. If "film"is referred to at this point or also later, this meansany possible material web in this case, irrespective ofwhether it is termed a plastics film or just a film.According to the invention, this is ensured by apreferred specially configured protruding section thatis provided or configured around the ventilationopenings. Alternatively or preferably supplementary tothis, the ventilation wall has a specific designcomprising side flanges opposite the nozzle box in thetransverse direction, said side flanges overlapping theside walls of the nozzle box outside of the interiorspace of the nozzle box.In a preferred variant design, this protruding sectioncan be made in the ventilation wall of the nozzle boxthat preferably consists of a metal sheet wall by meansof a simple embossing process and for this reason isformed as an indentation or a deep-drawn deformation inthis sheet wall. In other words, the correspondingventilation openings comprising the aforementionedprotruding sections can be created in the nozzle boxesin one single, simultaneously executed stamping and / orembossing process.The form of the protruding sections can be configureddifferently, wherein an outer boundary of theventilation protrusion is preferred that tapers at leastslightly conically from the plane and the external sideof the ventilation wall in the direction of theprotrusion. The configuration of the protruding sectionsis, in particular in the case of circular ventilationopenings, thus preferably frusto-conical, i.e.comprising a flattened end face for the protrudingsections, wherein this end-face section surrounding theventilation openings, for example in the case ofcircular or oval ventilation openings, has a width thatcan preferably vary between 0.5 mm and 5 mm.The opening angle of the cone, thus the angle of theouter boundary of the protruding sections that is moreor less steeply angled and surrounds the ventilationopenings must deviate only by the smallest angle inrelation to one of straight lines perpendicular to theventilation wall so that a cylinder is not formed.Angles of less than or equal to 89.75° are alreadyfavorable and have advantages for an embossing process.However, the angle itself can be or adopt a smallervalue, for example 45° or less. All values between thesespecified angles are also suitable.Moreover, provided in a preferred embodiment is that theventilation wall of the nozzle box provided withventilation openings is configured continuously in thetransverse direction of the nozzle box, thus is notassembled together by several laterally interconnectedventilation wall sections running parallel next to oneanother in the longitudinal direction of the nozzle box.As a result, oil is prevented from reaching the interiorof the nozzle box through slit-shaped gaps formed on thelateral flanges of such a multipart ventilation wall ofa nozzle box and being transported from there in turnfurther outwards by the supplied air via the ventilationopenings in the direction of the plastics film.Preferably, the continuous ventilation wall in thetransverse direction of the nozzle box is also providedexternally in each case with an angular flangeprotruding from the ventilation wall which overlaps theadjoining side wall of the nozzle box externally so thatoil here cannot reach the interior of the nozzle box.If the nozzle box consists of at least two or more partsdue to its large length, said parts are assembledtogether in the longitudinal direction, specificallyraised ventilation-wall edge sections are provided hereadditionally on the ventilation wall (in addition topreferably overlapping wall sections) so that no slitsextending from the top or external side into theinterior of the nozzle box are configured here, saidslits ending on the plane of the top side or surface ofthe nozzle openings, via which oil could penetrate intothe interior of the nozzle box.The aforementioned protruding sections and this inparticular their heights can be very small in sizewithin the scope of the invention.Ultimately, the aforementioned protruding section canalso be configured in such a way that not only oneventilation opening, but for example two ventilationopenings (or even more) are configured in the raisedflat elevation. In other words, a discrete, separateprotrusion must not be configured for each ventilationopening.Further advantages, specifications and features of theinvention are found hereinafter in the embodiments shownby means of the drawings.Thus, shown in detail:Figure 1: a schematic spatial view of a nozzle boxaccording to the invention;Figure 2: a schematic cross-sectional view in thetransverse direction and perpendicular to thelongitudinal direction of the nozzle box shownin Figure 1;Figure 3: an enlarged detailed view of a ventilationopening in the region of a protrusion in crosssectionthat is configured on a ventilationwall of the nozzle box shown in Figure 1 and 2;Figure 4: a partial spatial view of two protrusionssituated adjacent to each other comprisingventilation openings formed therein;Figure 5: a slightly modified embodiment of Figure 3 and4;Figures 6a to 6c: three partial perpendicular cross10sectional views in the longitudinal directionof two nozzle channel sections that can beassembled together in these regions at the endfaces, and namely once before the assembly,during being slid together on the end faces andafter the completed end-face assembly of twonozzle boxes;Figures 7a to 7c:three different examples in top view forclarification of how ventilation openings canbe configured and aligned differently;Figure 8: a schematic view of a ventilation modulecomprising four nozzle boxes according to theinvention that are arranged in a parallelconfiguration and offset to one another withthe lateral offset in the drawing direction ofa material web; andFigure 9: a schematic end-face view of several nozzleboxes arranged above and below the material webin the drawing direction of a plastics filmweb, wherein drainage and / or collectioncontainers for collecting the oil are locatedbetween the nozzle boxes arranged underneaththe material web.In the following, reference is made to a firstembodiment of a nozzle box according to the invention.This nozzle box 1 comprises a longitudinal direction L,and transverse direction Q and a height H. It isrectangular in shape in cross section, although thiscross-sectional shape is not obligatory.In the embodiment, the shown nozzle box 1 thus comprisesa base 3a and two opposing side walls 3b that in theshownembodiment run parallel to one another with alateral offset and are thus aligned perpendicular to thebase 3a. What is termed a ventilation or nozzle wall 5is provided above the base 3a at a distance H inrelation to the base 3a.The aforementioned side walls 3b and the base 3a as wellas the ventilation or nozzle wall 5 thus surround aninterior space 2 that is also referred to as the supplychamber 4 for supplying air which can then exit throughthe ventilation openings explained hereinafter. In theshown embodiment the nozzle box 1, as mentioned, thuscomprises a rectangular cross-sectional shape, althoughanother cross-sectional shape is possible. Thus, theside walls can also be designed to be curvilinear andmerge into a base that also extends, for example,continuously in a curve in cross section without theside walls being separated from the base by clear edges.Thus, in this respect in the scope of the invention, thespecific shape of the cross section of the nozzle box isnot important.In the ventilation or nozzle wall 5 extending in thelongitudinal direction L, a plurality of ventilationopenings 7 is configured that hereinafter is referred toin part also as nozzle openings or ventilation openingsor in general as openings 7 irrespective of the specificshape of their opening (thus for example as round, slip10shaped or quadratic openings etc.). In the shownembodiment, these ventilation openings 7 are configurednot only situated offset to one another in theventilation or nozzle wall 5 in the longitudinaldirection L, but also in several rows R positionedoffset to one another in the transverse direction Q. Ithas already been mentioned here that the shape of theseventilation openings, as well as the arrangement in thelongitudinal direction L and the transverse direction Q,can freely deviate from the shown embodiment, theseventilation openings 7 must not be arranged in relationto each other in fixed predefined rows R.As can be seen from the shown embodiment according toFigure 1, the nozzle box 1 comprises or can comprise twonozzle box sections 1a and 1b which are separated in thelongitudinal direction L, said sections being attachedand / or assembled together at least directly on end facesassigned to each other at an interface 9 thus formed forincreasing the total length, in particular can beassembled at this interface 9 on site.Illustrated by means of Figure 2, a schematic crosssection is depicted through the nozzle box 1 in thetransverse direction Q, thus perpendicular to thelongitudinal direction LAs can be seen here, the ventilation openings 7 areprovided and configured in the ventilation or nozzlewall 5 in the form of protrusions 13 or in the region ofsuch protrusions 13. As the nozzle box 1 and inparticular its ventilation or nozzle wall 5 primarilyconsists of one sheet, in particular a metal sheet, theformed ventilation openings / nozzle openings 7 thusformed and the corresponding protrusions 13 arepreferably produced in a joint simultaneous embossingand stamping process.In the shown embodiment according to Figure 2 as well asthe enlarged section view through the protrusion 13 ofthe ventilation opening 7 according to Figure 3 and thepartial spatial view of two protrusions 13 according toFigure 4, the surrounding external boundary wall 15 isformed conically or at least slightly conically.This external boundary wall 15 is thus raised convergingconically from the ventilation wall 5 and the top sideor surface 5a of the ventilation wall 5 formed as aresult, thus frusto-conical in the shown embodiment. Theactual ventilation opening 7 is limited by an encirclingopening edge 17 that thus forms a blunt and thus craterfreefinal area for the ventilation openings 7. What istermed a "crater-free" final area is important if a filmis being considered in particular as the material web.As it is to be ensured that even in the case of the filmcontacting the encircling opening edge 17 in the regionof the ventilation openings 7 that the film is notruptured or damaged or even torn as a result of cratershapedfraying out of the metal. In the shownembodiment, this opening edge 17 is configured andaligned at least roughly parallel to the top side orsurface 5a of the nozzle wall 5. This opening edge 17does not necessarily have to be aligned parallel to thetop side or surface 5a of the nozzle wall 5. Thisopening edge 17 can also still be designed curved in thesection perpendicular to the surface 5a, for exampleconvexly with preferably increasingly smaller angulardeviations in the direction of the ventilation openings7 in relation to the top side or surface 5a.Similarly, the opening edge 17 could be alignedpreferably with at least one small angle in relation tothe top side or surface 5a of the nozzle wall 5. Thus,this opening edge 17 can increase at a small angle inrelation to the plane of the surface 5a from the outeredge towards the actual ventilation opening 7, forexample at an angle of less than 45°, less than 30°,25°, 20°, 15°, 10° or less than 5°.The height H of the protrusion 13 can be very small insize, for example between 0.5 mm and 10 mm. The width ofthe encircling opening edge 17 can also be designed tothe same scale.The slightly conically diverging configuration of theprotrusions 13 is preferred if this protrusion 13 iscreated by means of an embossing process. However, evenif the ventilation wall 5 is supposed to be cast from aplastic, such a configuration would be advantageous asthe injection molding tool can then be withdrawn moreeasily from such a shaped protrusion. Preferably, theprotrusions 13 are however manufactured in oneprocessing step together and simultaneously with theventilation openings 7, for example using an embossingand stamping process particularly in the case of a metalsheet or using plastic injection molding if theventilation or nozzle wall 5 is supposed to be made ofplastic.Using Figure 5, it is shown deviating from Figure 3 inthat the encircling external boundary wall 15 could alsobe configured in principle cylindrically, wherein astill slightly conical configuration is also preferredin this embodiment, said configuration extendingdivergently slightly conically in particular from thetop side 5a of the nozzle wall 5. Hence to avoid acylindrical configuration, the angle of inclination α(between the conically inclined boundary wall 15 and theplane of the corresponding ventilation wall 5 - Figure3) can thus be less than 90°, for example thus amount to89.75° or less, in particular thus less than 89.5°,89.25°, 89°, 88°, 87°, 86°, 85°, 84°, 83°, 82° or 81° or80° are advantageous. In other words, this angle is thusalso preferably less than 60°, 50°, 45° or 40°, whereinthe cone configuration then increases however in thedirection of the surface of the ventilation wall 5.Illustrated by means of Figures 6a to 6c, in each casein a partial longitudinal section, two adjoiningventilation walls 5, for example, of two nozzle boxsections 1a and 1b to be assembled on site are shownbefore their assembly, during their assembly and aftertheir assembly.As can be seen from this, the ventilation wall 5comprises a ventilation wall edge section 5b protrudingat least in the direction of the end face 22, saidventilation wall edge section 5b being flanged with anext nozzle box in the direction opposite to theassembly direction, thus is preferably bent for exampleby 180°, and thus rests on the top side 5a of theventilation wall 5 in the form of more or less a narrowedge strip. Through this flanged edge strip, anotherprotrusion or another protruding section 113 is thusformed, wherein this protrusion 113 or this protrudingsection 113 forms a raised section running from the leftto the right lateral edge of the nozzle box so that nooil can reach the interior of the nozzle box via a slitor assembly slit existing between two nozzle boxesassembled on their end faces.This protective measure is increased even further as aresult of providing one of two face-end ventilationwalls 5 to be assembled in their end-face assemblyregion in the interior of the nozzle box 1 comprising atleast one material tongue extending across a part of thelongitudinal length of the nozzle box 1, 1b or a flange19a. This material tongue 19a or this flange 19aprojects out towards the adjoining next nozzle box 1aand is received into the adjoining end face 22 of thenext nozzle box 1 in a recess 19c configured there. Itis thus possible to assemble together two consecutivenozzle box sections 1a and 1b with overlapping wallsections 5 in the longitudinal direction. Here, inFigure 6a, both end faces of the nozzle boxes are shownin part before their assembly together, in Figure 6bwhen being brought together axially and in Figure 6cafter being finally fixed together when the materialtongue protruding over the end face 22 of said onenozzle box 1b or the protruding flange 19a is receivedand enters into the end face 22 of the adjoining nextnozzle box 1b and thus the dividing line 23 (Figure 6c)comes to rest between the corresponding flangedventilation wall edge sections 5b above this materialtongue 19a. As a result, the slit 23 still present atthis site is covered and sealed to the interior space ofnozzle box.As a result, the configuration prevents even thesmallest slits in the assembly region through which oildeposited initially on the top side 5a of the nozzlewall 5 could penetrate into the interior space 2, thusthe supply chamber 4. It therefore ensures that nodroplets of oil can be carried along through the airsupplied to the nozzle box 1 at the end face andconveyed again through the ventilation openings 7towards the plastics film.Thus, the overlapping arrangement of the ventilation ornozzle walls 5 in its end-face assembly area ensuresthat oil deposited on the top side 5a of the nozzle wall5 only drains off outwards - thus towards the opposinglongitudinal side of the nozzle box 1 - and does notpenetrate into this nozzle box.In critical cases, a sealing material can also be usedadditionally which is applied during the assembly. Thissealing material would then be provided in the regionbetween the top side of the material tongue 19a and theunderside of the wall section 5c located above.Therefore, the aforementioned wall section 5c would bethat region which comes to rest exactly above thecorresponding section of the material tongue 19a in thefinal assembled state, in other words thus that wallsection 5 that faces the interior space 2 of the nozzlebox 1 below the preferably flanged edge section 5b. In adisassembly, this seal would then have to be thenremoved (for example be scratched away) and a newsealing material would have to be applied during the reassembly.The sealing material can be, for example, ahigh-temperature silicone or a similar or comparablematerial which retains its seal tightness even at hightemperatures of >150°C.However, as a rule, such sealing material is notnecessary at all.Additionally, it is noted that, for example, also areinforcement and / or stiffening 28 can be provided onthe inner side 2 of the nozzle box 1 below theventilation or nozzle wall 5, but does not have to beprovided, as is shown for example in Figures 6a to 6c.This reinforcement and / or stiffening 28 can be designed,for example, to be wall-shaped, rib-shaped or webshaped,wherein here all possible design forms can betaken into consideration.This is also the goal of the edge lips 21 shown in thecross section using Figure 2 and configured on thelateral edge region 20 of the nozzle wall 5, said edgelips 21 each being developed opposite the ventilation / nozzle wall 5 in such a way that they overlap the sidewalls 3a externally, thus do not come to rest in theinterior space 2 of the nozzle box. In particular, thisventilation / nozzle wall 5 comprising theventilation / nozzle openings 7 is continuous in thetransverse direction Q, thus for example not dividedinto two, so that even here slits or gaps cannot occurbetween separate assembly parts formed in such way,through said slits or gaps for example theaforementioned oil exuded from the plastics film duringthe stretching process can enter into the interior ofthe nozzle box 1.Using Figure 7a, it is partially shown schematically intop view that the ventilation openings 7 can alsocomprise completely different designs or shapes, forexample can be designed oblong in shape, wherein theseventilation openings 7 can also be provided again inseveral rows R next to each to other.Using Figure 7b, a similar configuration is showncomprising ventilation openings 7 with elongated holetypes that can be provided however at an inclination,thus at an acute angle to the longitudinal direction Lof a nozzle box 1, for example, with 45° + less than 10°or less than 25°.Using this view according to Figure 7c, it can be shownexemplarily that such elongated holes can be alsoconfigured in the transverse direction Q, thusperpendicular to the longitudinal direction L in theventilation wall of a nozzle box.What is common to all embodiments is that theprotrusions 13 (with said at least one or moreventilation openings 7 formed thereon) are provided onthe top side 5a of the nozzle wall 5 under theconfiguration of spacings to each other in such a waythat also oil deposited adjacent to the protrusions 13on the top side or surface 5a of the ventilation andnozzle wall 5 can flow away to the left or right edge ofthe nozzle box (thus in the transverse direction Q ofthe nozzle box) and from there downwards - at least withregard to the nozzle boxes arranged under the plasticsfilm, in the case of said nozzle boxes, the nozzleopening being situated aligned upwards towards theunderside of the plastics film. In other words, manybridges of material 35 thus exist which extend on thetop side 5a from the left to right lateral edge of thenozzle wall 5 so that oil deposited on the top side orsurface 5a of the ventilation or nozzle wall 5 canalways flow past the protrusions 13 to the lateral edgeof the nozzle box.Ultimately, reference is made to the view according toFigure 8 in which nozzle boxes can be seen arranged inthe transverse direction to the drawing direction 25 ofa plastics film F, i.e. their end-face view, which arearranged spaced apart from each other below the plasticsfilm F in the drawing direction. Typically,corresponding nozzle boxes are also arranged with thesame spacing in the drawing direction and using the samevertical spacing above the control film / the materialweb, namely with its ventilation openings situatedaligned on the top side of the plastics film, as isshown in Figure 9.Using Figure 9, it is now indicated that the nozzle box1 can have drainage devices 29 laterally, mainly in theform of oil grooves. Preferably, these are arranged at acertain angle so that the oil can drain optimally. Thus,the oil could be trapped in these grooves and collectedin the collection container 31 via outflows. Inaddition, it is possible that intermediate sheets areplaced between the nozzle boxes which are designed roof10shaped and also drain off the oil in grooves. This isadvantageous as the oil can be collected and the ovenbase is also not soiled by oil.In particular, this would be conceivable or evennecessary for a simultaneous stretching process (LISIM)as in this process transverse as well as machinedirection stretching occurs in the oven. In the case ofa sequential stretching process, the machine directionstretching occurs in a machine (MDO) preceding the oven.Much of the oil is already squeezed out in MDO and doesnot reach the oven. It can therefore be expected thatthe problem of oil contamination in the oven is evengreater in a simultaneous stretching process or in atransverse stretching stage following a machinedirection stretching process and thus a significantadvantage can be attained by means of the invention.

Claims

1. Nozzle box having the following features: - side walls (3b) spaced apart from each other, a base (3a) and a ventilation wall (5) spaced apart from it, thereby forming an interior space (2), - a plurality of ventilation openings (7) arranged offset to each other is provided in the ventilation wall (5), - the nozzle box (1) is provided on its ventilation wall (5) with a plurality of protrusions (13) that are raised by at least a height (H) in relation to the sections of ventilation wall (5) or the top side or surface (5a) of the ventilation wall (5), said sections being situated adjacent to the protrusions (13), - the ventilation openings (7) are arranged and configured in the region of the protrusions (13) in relation to the top side or surface (5a) of the ventilation wall (5) positioned offset to each other in such a way that they are further away in relation to the interior space (2) than the top side or surface (5a) of the ventilation openings (5) adjacent to the protrusions (13), and / or the ventilation wall (5) comprises in the transverse direction (Q) of the nozzle box (1) opposing side flanges (19a, 19b) that overlap the side walls (3b) of the nozzle box (1) outside the interior space (2) of the nozzle box (1).

2. Nozzle box according to claim 1, characterized in that the protrusions (13) comprise a boundary wall 15 extending around each one or around at least two or more ventilation openings (7), said boundary wall (15) extending at an acute angle of inclination α in the cross-sectional view at least in part and / or aligned at least in part perpendicular to the ventilation wall (5) away from the interior space (2).

3. Nozzle box according to claim 2, characterized in that the angle of inclination α is less than 90°, in particular less than 89.75° or less than 89.5°, 89.25°, 89°, 88°, 87°, 86°, 85°, 84°, 83°, 82°, 81°, 80°, 70°, 60°, 50°, 45° or 40°, and primarily is greater than 50°, in particular greater than 60°, 70°, 80°, 81°, 82°, 83°, 84°, 85°, 86°, 87°, 88°, 89°, 89.25° or is greater than 89.5°.

4. Nozzle box according to claim 1, 2, or 3, characterized in that the protrusions (13) are configured converging conically at least in a partial height in a direction extending away from the interior space (2).

5. Nozzle box according to claim 1, 2, 3 or 4, characterized in that the end section of the protrusion (13) situated away from the top side or surface (5a) of the ventilation wall (5) is configured to be crater-free and / or blunt, primarily in the form of an opening edge (17) surrounding the corresponding ventilation opening (7), said opening edge (17) being aligned in particular parallel to the top side or surface (5a) of the ventilation wall (5) or deviates from it less than 45°, in particular less than 30°, 20° or less than 10° or 5°.

6. Nozzle box according to any one of the claims 1 to 5, characterized in that the protrusion (13) comprises a height in relation to the top side or surface (5a) of the ventilation wall (5) that is greater than 0.5 mm or is greater than 1.0 mm, 1.5 mm, 2.0 mm, 2.5 mm, 3.0 mm, 3.5 mm, 4.0 mm or 4.5 mm, and / or the protrusion (13) comprises a height in relation to the top side or surface (5a) of the ventilation wall (5) that is less than 5.0 mm or less than 4.5 mm, 4.0 mm, 3.5 mm, 3.0 mm, 3.5 mm, 2.0 mm, 1.5 mm or 1 mm.

7. Nozzle box according to any one of the claims 1 to 6, characterized in that the ventilation openings (7) or at least a part of the ventilation openings (7) in top view are configured circular or oblong or n-polygonal in shape and that the protrusions (13) comprising ventilation openings (7) positioned preferably centrally therein comprise a shape in top view that corresponds to the shape of the ventilation openings (7) or is similar to this.

8. Nozzle box according to any one of the claims 1 to 7, characterized in that the ventilation openings are arranged or configured spaced apart in the longitudinal direction L of the nozzle box in one or in several rows provided in the transverse direction (Q) of the nozzle box (1) in such a way that the two lateral edges (20) of the ventilation wall (5) are connected to each other via bridges of material (35).

9. Nozzle box according to any one of the claims 1 to 8, characterized in that at least two ventilation openings (7) are arranged in a shared protrusion (13) that are surrounded by a shared encircling boundary wall (15).

10. Nozzle box according to any one of the claims 1 to 9, characterized in that the ventilation wall (5) comprises an ventilation wall edge section (5b) protruding on the end face in the region of at least one of its end faces (22), said ventilation wall edge section (5b) protruding on the end face being bent from the plane of the ventilation wall (5) opposite the interior space (2) and preferably resting bent over or flanged on the top side (5a) of the ventilation wall (5), thereby forming a mainly strip-shaped protrusion (113) protruding in relation to the top side or surface (5a) of the ventilation wall (5) and / or situated higher.

11. Nozzle box according to any one of the claims 1 to 10, characterized in that the nozzle box (1) in its longitudinal direction (L) comprises at least two nozzle box sections (1; 1a, 1b), wherein at least one nozzle box section (1a or 1b) is provided on the inner side the ventilation wall (5) with a material tongue extending in the assembly direction or a flange (24) that protrudes on its end face from the corresponding end face (22) of the nozzle box section (1a or 1b) and is received into a corresponding recess (19c) in the adjoining next nozzle box (1; 1b or 1a) and in doing so covers a gap (23) existing optionally between the two flanged ventilation wall edge sections (5b) adjoining each other in the interior (2) of the nozzle box (1) and seals said gap (23) in relation to the interior space (2) of the nozzle box (5).

12. Nozzle box according any one of the claims 1 to 11, characterized in that the protrusions (13, 113) - are formed by embossing into the ventilation wall (5) made of a metal sheet and / or - are formed from a mounted material fixture firmly connected to the ventilation wall (5) in a manner impermeable to oil.

13. Stretching unit comprising a nozzle box according to at least one of the claims 1 to 12.

14. Stretching unit according to claim 13, characterized in that the several nozzle boxes (1) arranged offset to each other in the drawing direction (A) of a plastics film (F) underneath the plastics film (F), and that a drainage device (29) and / or a receiving device (29), in particular in the form a collection container, for the oil flowing away from the top side or surface 5a of the ventilation wall (5), is provided between at least two nozz.l-e boxes offset to each other in the drawing direction A.