Abstract:
A method is disclosed for winding a continuous web of material on a core mandrel, the winder comprising a cutter that actuates to provide a new end of web material. The cutter itself comprises a source of vacuum for creating an airflow around a new core mandrel between the mandrel and a guide wall which extends around at least one fourth of the mandrel surface, the airflow causing the new web end to follow the mandrel around and tuck said new end between the mandrel circumference and the tensioned web extending between the new mandrel and upstream equipment.

Description:
FIELD OF THE INVENTION 
     The invention relates to a method for winding a continuous web of material onto a series of core mandrels, to a device for cutting the web on changing the core mandrels, to a web winding device and to the application of the method. 
     BACKGROUND OF THE INVENTION 
     Web winders and web winding methods are known in various embodiment forms and are e.g. described in DE-A 2 243 504, EP-A-0 017 277, EP-A-0 394 197 and CH-A-683 992 and the state of the art is described in these documents. Common to the known winders is that a relatively quick running and more or less endless material web of plastic foil, paper textile material or another relatively thin (typically 10 to 1000 μm thick) and flexible material with working widths of up to a few meters either in the course of the manufacture of the web material or with its processing must be continuously wound, i.e. without interruption of the flow of material, onto a series of core mandrels which are fed to the winder from a winding reel magazine. 
     With this there are in particular two problems to be solved, specifically on the one hand a very rapid, clean and precise separation or cutting procedure is to be effected and on the other hand the front end of a new web section is to be brought into winding contact with a fresh, i.e. empty core mandrel. An approximately right-angled cutting procedure with high web running speeds may only be achieved with a knife acting suddenly, e.g. within 0.1-0.5 seconds, over the whole web width, which with web winders for the production or processing of typical technical plastic foils is mostly a serrated knife, as is described in CH-A-674 352. According to the transverse cutting method described in the above mentioned patent document DE-A-2 243 504 a knife or blade with a relatively high speed is guided transversely over the material web, which leads to an oblique cut. 
     For achieving the winding contact for the winding of a core mandrel which is still empty usually adhesives or adhesive tapes are used. This in practice has various disadvantages such as the lessening of the effectiveness of the adhesive layers by dust, the unwanted contamination of adhesive or adhesive tape into the winding and the use of organic solvents. Suggestions for achieving the winding contact by way of electrostatics, such as e.g. in EP-A- 0 270 498 and the state of the art described therein have not been able to be sustained in practice up to now on account of the required high voltages and the consequences of a change in air humidity. 
     A common disadvantage of the known methods and devices is a more or less heavy jerk with the winding procedure which may lead to disadvantageous effects on premounted, i.e. on the upstream side manufacturing, processing or refining units. 
     BRIEF SUMMARY OF THE INVENTION 
     It is the object of the invention to offer a winding method which does not have the mentioned disadvantages or only to a negligible extent. The object of the invention is also an improved cutting device and a new web winder. 
     These objects are according to the invention achieved by a method for winding a continuous web of material onto a series of core mandrels of a winding device which has a winding roller, at least one movable deflection roller and a cutting device, characterised in that the front end of the web formed on actuation of the cutting device, under the effect of an arc-shaped airstream which extends around at least roughly a quarter of the spool circumference, at least approximately over the width of the core mandrel and up to the vicinity of the contact line between the winding roller and the bearing core mandrel, is brought into winding contact with the core mandrel. 
     The description “winding contact” used here means a contact between the core mandrel and the new front web end formed by cutting the web, which is sufficient for winding a fresh core mandrel. 
     The speed of the airflow is preferably twice in particular three times and e.g. six times greater than the material web running continuously with web running speeds of 30 to 400 meters/minute or more. 
     Preferably every winding roller, thus that of the preceding finished winding as well as that of the fresh subsequent winding is connected to a central drive which may be controlled such that the tensile stress acting on the web may be kept to a desired value and is not dependent on the thickness of the respective winding. In a useful manner for this a drive acting from the left side and one from acting the right side of the winder is used. 
     Preferably the arc-shaped airstream is produced by a reduced pressure, e.g. from −450 to −900 millibar, acting in the vicinity of the contact line between the winding roller and the core mandrel bearing on this. According to a preferred embodiment form of the method the formation of the arc-shaped airstream is supported by lateral afflux streams which are produced by the pressure difference between the applied reduced pressure and the surrounding pressure, or a hyperbaric pressure from an excess pressure source. 
     Generally it is preferred that the web on actuation of the cutting means contacts the core mandrel over roughly half its circumference. 
     In order to make the cutting procedure practically jerk-free, it is useful to keep the web path, with the help of a reduced pressure applied in the inside of the winding roller, on the winding roller provided with openings of the roller casing. For improving the contact of the web with the core mandrel in the inside of the core mandrel provided with openings there is applied a reduced pressure. 
     The cutting device according to the invention, for a device for winding a continuous web of material onto a series of core mandrels is characterised in that the cutting device has a reduced pressure channel which extends practically over the length of the core mandrels and which is connected to a guiding wall encompassing in an arc-shaped manner the core mandrel about at least a quarter of its circumference and to a serrated knife, in order to bring the front end of the web, which is formed on actuation of the cutting means, under the effect of an arc-shaped airstream extending at least around a quarter of the spool circumference at least approximately over the width of the core mandrel and up to the vicinity of the contact line between the winding roller and the bearing core mandrel, into winding contact with the core mandrel. Preferably the cutting means is connected to a means for pivoting the knife into the path of the web between a fresh core mandrel bearing on the winding roller and a movable winding roller which is brought into a position near to the core mandrel. 
     The device, according to the invention, for winding a continuous web of material onto a series of core mandrels includes a winding roller, at least one movable deflecting roller and a means for severing the web in order on this to form a web end thereon passing onto a preceding full core mandrel and a web end envisaged for winding on the subsequent empty core mandrel, and is characterised in that the cutting device has a reduced pressure channel which extends practically over the length of the core mandrels and which is connected to a guiding wall encompassing in an arc-shaped manner the core mandrel about at least a quarter of its circumference and to a serrated knife, in order to bring the front end of the web, which is formed on actuation of the cutting means, under the effect of an arc-shaped airstream extending at least around a quarter of the core mandrel circumference at least approximately over the width of the core mandrel and up to the vicinity of the contact line between the winding roller and the bearing core mandrel, into winding contact with the core mandrel. 
     Preferably the winding roller ( 21 ) has a casing provided with a rubber coating, e.g. of steel, and openings, in order by way of a reduced pressure prevailing in the inside of the winding roller to hold a bearing web in reinforced contact and to permit a practically jerk-free winding operation. 
     Finally the invention relates also to the application of the new cutting method for winding practically endless webs or tapes in the course of the manufacture of a foil, e.g. by extrusion, or of the processing, e.g. by cutting apart, pressing or other processings of the webs. The description “practically endless” relates to web or tape lengths, which in relationship to the web or tape width are very large, e.g. at least greater by the factor 1000. Suitable plastic foils are such with thicknesses in the region of typically between 5 and 1000 μm of known polymers, copolymers, propypolymers, polmer mixtures with film-forming molecular weights including the usual additional substances for the foil manufacture and processing. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention is described in more detail by way of the accompanying drawings. There are shown: 
     FIG. 1 a schematic representation of the course of a cutting device according to the invention; 
     FIG. 2 a schematic part view of a cutting means according to the invention in combination with a winding device according to the invention and 
     FIG. 3 a modification of the cutting means according to the representation in FIG.  2 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The schematic drawing of FIG. 1 shows the cutting and winding procedure of a device  15  in five steps (I-V). It must be stressed that this subdivision serves only for the explanation and the procedure runs actually continuously. In the first step I there is shown the material web B, e.g. a paper or textile material web coming from an extruder, which runs over the winding roller  11  and which is wound onto the bearing, almost full material web winding  12  around the preceding core mandrel  14 . The almost full winding  12  is held laterally on the winding roller  11  by a pivotable pair of arms  120  usually described as a “winding station” (only the front arm is shown in FIG. 1) in a desired position with the desired pressing force controlled in the desired or in the known manner (see e.g. the two previously mentioned European Patent specifications). A pivotable embodiment form of the winding station  120  is however for the present invention not critical and may be formed differently, e.g. as a carriage which can be traversed in a controlled manner with a vertical support. 
     An empty fresh core mandrel  16  with a guiding spike (not shown) is supplied from a magazine (not shown) of the usual construction and a deflection roller  18  is guided out of its idle position in the direction of the foil web B on the winding  12 . 
     In the following step II the deflection roller  18  gets into contact with the foil web B on the foil winding  12  whilst simultaneously an empty core mandrel  16  with the help of a usual (not shown for an improved overview) pivoting arm pair (described as a winding station) is guided in the direction of the gap between the winding roller  11  and the foil winding  12  until the deflection roller  18  contacts the foil winding  12 . 
     In step III the foil winding  12  by pivoting (or traversing) the winding station  120  is removed from the winding roller  11  whilst the empty core mandrel  16  and the deflection roller  18  is moved into the position which is represented in step IV of the schematic drawing of FIG. 1, i.e. the deflection roller  18  contacts the foil winding  12  and for this after finishing the contact with the winding roller  11  serves as a feed roller, and specifically preferably in a position above the contact line between the winding roller  11  and the foil winding  12 , which exists before the ending of the contact. The web B runs in step IV further onto the foil winding  12 , however with the diversion around the still empty core mandrel  16  and the deflection roller  18 . 
     From now the cutting means  10  is guided in the direction of the material web B in the region between the empty core mandrel  16  and the deflection roller  18 , where the material web runs freely, i.e. neither contacts the deflection roller  18  nor on the empty core mandrel  16 . Between the deflection roller  18  and the empty core mandrel  16  thus there must exist a sufficient distance so that the cutting device  10  now guided to the web B may impinge and finally (step V) sever the material web B in the region of its free running between the deflection roller  18  and the still empty core mandrel, so that a “rear” end of the foil web B running out onto the foil winding  12  and a “front” end of the continuously further running foil web B envisaged for winding onto the still empty core mandrel  16  are formed. 
     The details of the now following winding on procedure according to the present invention by way of an airstream are initially described in combination with the following FIGS. 2 and 3. In the step IV following the winding on procedure of the schematic drawing of FIG. 1 it is yet indicated how the winding station  120  after removal of the completed foil winding  12  assumes the core mandrel  16  with the foil web B which in the meantime has been wound thereon, from the (non-shown) winding station and keeps in contact with the winding roller  11  until the subsequent path separation and winding on procedure. For understanding the invention it is yet to be supplemented that the winding station as well as also preferably the winding on station for operation as a central winder is connected to a (non-shown) controllable rotational movement drive, in order to control the pulling tension acting on the web in a known manner in dependence on the material parameters, such as type, property and thickness of the web material, and on the desired linear pressure on the gap between the winding roller  11  and the bearing foil winding  12 . 
     In any case the front end of the subsequent web section is wound onto the empty core mandrel  16  so that the (non-shown) central drive which is brought into engagement with the core mandrel  16  may exert the spool tension adapted to the winding procedure. The exact operating parameters (contact pressure on the gap between the web winding and the winding roller; pulling tension and running speed) are dependent in the known manner on the type of the winding device  15  and the web material and may by experts be optimised by way of a few less simple trials. 
     The essential difference between the method according to the invention and the state of the art then lies in the manner in which the winding contact required for the winding on is achieved. According to the state of the art this contact is either achieved with the help of an adhesive (e.g. in the form of an adhesive tape on the surface of the core mandrel) or by way of electrostatic charging of the foil with respect to the core mandrel. With the method according to the invention in this manner the formation of the winding contact is done away with, i.e. neither adhesive in any type of form nor an electrostatic charging is used, and the new “front” end of the material web with the help of an airstream is guided onto the core mandrel and is held on this for so long until the continued rotation of the winding roller effects a rigid clamping of the web end between the surface of the core mandrel and the following layer of the material web which is wound thereover. This new winding on method is here also described briefly as a “pneumatic winding on” and is subsequently described in detail. 
     In FIG. 2 schematically and by way of a cut-out a winding device  25  with a cutting means  20  according to the invention is shown, which in the manner shown in FIG. 1 is guided into the path of the material web B between the core mandrel  21  and the movable deflection roller  28 . The cutting means  20  is provided with a knife  201 , which in a manner not shown but in the known manner is formed as a serrated knife and extends over the whole width of the material web B. With the contact of the knife  201  with the web B this web within a very short space in time of e.g. 0.1-0.5 seconds is abruptly severed and by way of this the rear web end E 0  running out around the deflection roller  48  on the (non-shown) completed web winding as well as the “new” or “front” web end E 1  is formed. The latter is blown onto the surface of the core mandrel  26  by an arc-shaped airstream L and is held on this in winding contact. 
     The arc-shaped airstream L arises by way of the fact that by way of a bent conducting or guiding wall  203  extending at least over the whole width of the material web B and by way of the neighboring surface of the core mandrel an arc-shaped space is formed whose end neighboring the winding roller  21  is connected to a reduced pressure channel  200 . The channel  200  may be a housing which is connected to the knife  201  and which is formed by the guiding wall  203 , the wall  204  running near the winding roller  21 , the rear wall  205  and the upper wall  206 . The channel  200  has a slot-shaped opening  209  which extends over the channel width and which produces the airstream L. A guide plate  27  may serve for leading the path of the airstream L up to the vicinity of the winding roller  21 . 
     The (non-shown) lateral ends of the reduced pressure channel are closed or connected to a reduced pressure source, e.g. to a container (not shown) being under pressure which is continuously evacuated with suitable powerful pumps. 
     The winding roller  21  according to a preferred embodiment example of the invention with the application of air-impermeable web materials as in particular plastic foils or relatively compact paper, has a hollow inner space  210  which is likewise connected to a reduced pressure source (not shown) and holds most of the material web B bearing around about 180° of the circumference of the winding roller on the surface of the winding roller  21 , this surface for example consisting of a rubber layer  212  on the casing wall  211 . This measure has the particular advantage of avoiding jerk-like effects on the material web in the region between the winding roller  21  and an upstream-side region of the material web which e.g. in the context of manufacture of plastic foils by extrusion or similar methods is sensitive to jerk-like loads, for example by way of an uncontrolled drawing or hanging through and tensionings in the web caused by this or by way of orientation and strength differences caused by the drawing. 
     In FIG. 2 the core mandrel  26  is shown guided on a solid core spike  261 . It however lies within the scope of the invention to produce a reduced pressure also in the inside of the core mandrel  26 , this reduced pressure acting via channels  263  shown dashed onto the bearing material web path via channels  263  and suctioning this. 
     FIG. 3 shows a modification of the cutting means schematically represented in FIG. 2; with this the reduced pressure channel  300  is formed by a hollow body, e.g. a tube  39  which has a slot-shaped opening  309  for suctioning the airstream L. The connection to the knife  301  may be designed in any manner, e.g. in the form of a simple connection plating or clip, as long as only the arc-shaped guiding wall  303  remains intact. If it is desired the three features of the cutting means  30  which are essential to the invention—specifically the reduced pressure channel  300 , the arc-shaped guiding wall  303  and the knife  301  connected to this—may be unified with the walls  304 ,  305  and  306  to a hollow body which selectively is connected to the atmosphere or is under an excess pressure. In both cases with this the airstream L is supplied with additional air via the connection channels  322 , this air pressing the material web B against the core mandrel  36 . Also in the region of the transition of the knife  301  to the guiding wall  303  one or more openings  321  may be provided in order to produce an additionally laterally acting component of the airstream L. 
     Preferably the geometry, of all parts of a cutting means, which are essential to the invention, i.e. with the design of the guiding wall  203 ,  303 , of the knife  201 ,  301  and of the reduced pressure channel  200 ,  3000 , which are shown in the FIGS. 2 and 3, is formed such that the arc-shaped airstream L encompasses at least 90°, preferably at least 120° and in particular at least 140° of the circumference of the core mandrel and the material web bearing on the core mandrel up to the point in time of the web separation encompasses the core mandrel at least to 180° of its circumference. 
     According to a modified embodiment form (not shown) of the embodiment forms of a device according to the invention, described in the FIGS. 2 and 3, instead of a serrated knife  201 ,  301  a known transverse cutting device e.g. according to DE-A-2 243 504 is used which is connected to the housing  20 ,  30  and leads to an oblique cut. According to the invention thus also an obliquely running cut on the start of a foil section may be wound onto a fresh core mandrel without the known auxiliary means for winding on (adhesing and/or electrostatic adhesion) having to be used. 
     The cutting means according to the invention permits a design which is simple in comparison to the state of the art but however permits a secure operation and thus serves a row of further advantages: thus the cutting means—neglecting the knife which is mostly manufactured of steel, hard material or ceramics—may be manufactured of light metal so that the moved mass is comparatively small. With this the pivoting in and out may be effected in the usual manner with pneumatic or hydraulic actuating elements. The cutting means according to the invention may not only be installed in new installations but also existing installations for replacing the known cutting means. For the field of the man skilled in the art within the scope of the subsequent claims there results numerous modification.