Abstract:
An apparatus transfers a moving web of a flexible material from a web guide surface. The web guide surface outputs the moving web, and the moving web has at least one web edge. The apparatus includes at least one edge nozzle, each edge nozzle being positioned so as to be proximate one at least one web edge. Each edge nozzle is configured for separating the moving web from the web guide surface and is further configured to function as a severing device. Each edge nozzle is thereby configured for transversely severing the moving web and forming a new start portion thereof. Each edge nozzle briefly ejects therefrom a high-energy air jet, each high-energy air jet being ejected between the web guide surface and the moving web.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention.  
           [0002]    The invention relates to a method and an apparatus for transferring a web made of a flexible material, especially a paper web, from a web guide surface that outputs the web to a web conveying apparatus.  
           [0003]    2. Description of the Related Art.  
           [0004]    Normally, web transfer concerns the transfer of a threading tail, which is part (for example, an edge strip) of the aforementioned paper web. The transfer takes place, for example, from a first machine section to a following second machine section. Such machine sections can be, in particular, parts of a machine for producing or converting a paper web. For example, it concerns the transfer of the tail within or at the end of the press section of a paper making machine; within or to a winder; and/or from the end region of the drying section of the paper making machine to a following calender. This “tail transfer” is used to make threading the paper web into the machine easier.  
           [0005]    It is the intention of the present invention to improve the methods and apparatuses which are described in U.S. Pat. Nos. 3,355,349 and 4,501,643, and also in the brochure “Double Tail Elimination” from the FIBRON Machine Corporation, New Westminster B.C., Canada. Reference is also made to German patent application DE 199 62 731.2.  
           [0006]    U.S. Pat. No. 3,355,349 describes a vacuum belt conveyor for conveying a threading strip or tail of a paper web from the drying section of a paper making machine to the first nip of the calender thereof. The belt conveyor includes an elongated body and an air-permeable endless belt, which is mounted such that it can be moved on the body with the aid of two rollers. The endless belt has a conveying run (for example, its upper run). The conveying run travels from the region of the last drying cylinder to the region of the first nip of the calender. The belt is arranged in such a way that it picks up the threading strip from the last drying cylinder. The elongated body of the conveyor is designed as a vacuum box having a perforated upper part. The length of the vacuum box extends underneath the conveying run of the belt. Measures are provided to produce a vacuum in the box, in order to hold the threading strip on the moving belt.  
           [0007]    At the infeed end of the known belt conveyor, a severing device or tail cutter is fixed. The severing device or tail cutter is a toothed knife which extends in the transverse direction, i.e., parallel to the roller axis. Before the belt conveyor begins to transport the tail of a web, the complete web, including the tail, runs downward from the last drying cylinder “outputting the web”, past the inlet region of the belt conveyor, the web finally reaching a broke container or a broke pulper. A narrow “tail doctor” is provided on the last drying cylinder, in order to separate the tail from the outer of the drying cylinder and to transfer the tail to the belt conveyor. When the latter comes into action, the tail cutter severs the tail and, in this way, forms a new start of the tail, which is then transported to the calender. If no tail cutter were to be present, the belt conveyor would pull a piece of the tail upwards again out of the broke container and therefore transport a “double tail”. Transporting a “double tail” would cause problems during the threading operation (as addressed in the abovementioned brochure “Double Tail Elimination”).  
           [0008]    The belt conveyor design which is disclosed by US &#39;349 and by the referenced brochure has been tried and tested in operation. However, improvements are desirable with the aim that the belt conveyor be able to operate still more reliably and/or at an even higher working speed. In addition, a tail doctor should be avoided, since such an element causes impermissible wear of the outer surface of the drying cylinder.  
           [0009]    According to US &#39;643, an apparatus for the transverse severing and guidance of a tail is designed in such a way that it avoids moving parts and a cutting blade or knife. The tail is separated from the last drying cylinder with the aid of two edge blowing nozzles and is severed transversely with the aid of two pneumatic guide plates, which pull the tail in two different directions. The onward transport of the tail is then carried out exclusively by one of the pneumatic guide plates. It is doubtful whether this known design operates satisfactorily, at least when a paper web is to be transferred at a relatively high speed and/or when a very high operating speed is to be used.  
         SUMMARY OF THE INVENTION  
         [0010]    The invention is based on further developing methods and apparatuses with the effect that as many as possible of the requirements specified below are satisfied:  
           [0011]    1. It should be possible to carry out the transferring of the web or the threading tail more reliably than hitherto possible and to do so in the production as many different paper grades as possible, even at the extremely high operating speeds of a modem paper making or converting machine (for example, at 2000 m/min or above);  
           [0012]    2. On the web guiding surface that outputs the web (for example, roll or cylinder outer surface), a tail doctor that has previously frequently been required should be made superfluous;  
           [0013]    3. Likewise, a mechanical severing device (knife) for the transverse severing of the web or the tail is to be avoided;  
           [0014]    4. During the transverse severing of the web or the tail, damage to the web or tail edges is to be avoided as much as possible in the region of the new start of the web or the tail, in order that the web or the tail does not tear in its further course, even at an extremely high running speed. For the same reason, the most stable run possible of the web or the tail from the web guide surface that outputs the web to the following web conveying apparatus, possibly to the vacuum belt conveyor, is desired to be achieved; and  
           [0015]    5. It is to be possible to arrange the following web conveying apparatus (in particular, if present, the vacuum belt conveyor) as close as possible to the normal web running path, for example close to the web running path which runs through a scanner, as it is known.  
           [0016]    An important finding which has led to the invention is that the edge nozzles already known previously (see, for example, U.S. Pat. No. 1,688,267, FIG. 4, numbers  80  and  82 ) can be used not only to separate the paper web, in particular the tail, from the web guide surface that outputs the web, but, in addition, can also be used for the transverse severing of the web or the tail. This severing succeeds under the precondition that the edge nozzles eject a high-energy air jet, whose flow velocity is as high as possible yet only briefly so (ideally, if possible, only for a fraction of a second).  
           [0017]    According to additional concepts relating to the advantageous refinement of the apparatus according to the invention, in the inlet region, e.g., of a vacuum belt conveyor or a rope conveyor (e.g., a rope guidance system), a transfer subassembly is provided which is used specifically for the safe transfer of the web or the tail from the web guide surface that outputs the web. This subassembly includes a pneumatic guide plate with devices for producing an air flow running on the guide plate in the web running direction. In addition, the subassembly for the transverse severing of the web or the tail includes a separating and severing device, which is designed as at least one edge nozzle. The air supply to the at least one edge nozzle is designed in such a way that a high-energy air jet is ejected briefly, specifically being done so between the web guide surface that outputs the web and the web or the tail, so that the web or the tail is severed transversely immediately as it is separated from the web guide surface.  
           [0018]    An important idea which furthers the invention is making the aforementioned transfer subassembly (i.e., including guide plate and severing device) movable (for example, relative to the vacuum belt conveyor) such that the distance between the web guide surface that outputs the web and the aforementioned subassembly can be varied. In this way, during the threading operation, the subassembly can be positioned temporarily at a very short distance from the web guide surface that outputs the web. It is therefore possible for the gap between the web guide surface that outputs the web and the web conveying apparatus to be reduced, so that the size of the web or of the tail during the threading operation is reduced to the greatest possible extent. Before the threading operation (and possibly between successive threading attempts), the aforementioned subassembly can be positioned at a certain distance from the roll or cylinder that outputs the web. As a result, the web or the tail can run downwardly without hindrance (for example, into a broke pulper), so that blockages and/or damage to the web conveying apparatus are avoided.  
           [0019]    Because, according to the invention, both the separating of the web or the tail from the web guide surface that outputs the web and the transverse severing are carried out pneumatically with the aid of the edge nozzles, both an additional tail doctor, often required earlier, and a mechanical severing device are dispensed with.  
           [0020]    The transfer subassembly including a guide plate and severing device can be further configured to better promote the most secure transfer possible of the new start of the web or the tail. It is possible to provide additional blower openings immediately at the infeed end of the guide plate in order to produce an air flow that supports the transport of the web or the tail. These additional blower openings should preferably briefly eject high-energy air jets or a corresponding air curtain, preferably at the same time as the edge blower nozzles. As an alternative or an addition to such blower openings, the guide plate should have at its infeed end a so-called Coanda nozzle, such a nozzle having a rounded edge which, by using the Coanda effect, deflects an air flow (of the highest possible speed) in the direction of the guide plate. By this device, a vacuum zone is produced at the rounded edge and ensures secure guidance of the tail. This produced Coanda effect avoids the situation where the edge blower nozzles, in spite of only brief effect, compress the new start of the tail laterally after the transverse severing thereof. If the guide plate has a plurality of further blowing devices arranged one after another in the manner of a cascade, at least one of these further blowing devices can also be designed as a Coanda nozzle.  
           [0021]    According to a further, supplementary embodiment of the invention, at its end on the outlet side (i.e., close to the conveying run of the belt conveyor), the guide plate has an air guide channel, which is curved in such a way that it leads away from the running path of the web or the tail. This air guide channel has two effects. First, it ensures deflection of the air boundary layer carried along by the belt and therefore renders the latter undamaging (i.e., it is ensured that at most part of this air boundary layer passes to the point where the tail is gripped by the vacuum belt conveyor). In addition, the air flow led along on the guide plate is led on the shortest route into the suction zone of the vacuum belt conveyor, and the major part of such air flow is extracted there. As a result, the web or the tail is gripped securely by the vacuum belt conveyor and conveyed onwards as intended. The air guide channel acts in a similar way when the tail is transferred into the rope pinch of a rope guidance system.  
           [0022]    In operation, the operations mentioned above proceed at the full operating speed of the paper making or converting machine, for example at around 2000 m/min, and occur within a fraction of a second. Therefore, the features according to the invention form the basis for improved, successful threading operations, in particular in modem high-speed paper machines. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0023]    The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein:  
         [0024]    [0024]FIG. 1 is a schematic, side view of a tail transfer apparatus having a vacuum belt conveyor, arranged between a drying cylinder and a multi-roll calender of a paper machine;  
         [0025]    [0025]FIG. 2 is an enlarged view of the inlet region of the vacuum belt conveyor shown in FIG. 1;  
         [0026]    [0026]FIG. 2A is a view in the direction of the arrow A from FIG. 2;  
         [0027]    FIGS.  3 - 5  are schematic, side views of different embodiments of the tail transfer apparatus, located in the inlet region of the belt conveyor;  
         [0028]    [0028]FIG. 6 is a cross-sectional view of an edge nozzle designed as a Laval nozzle; and  
         [0029]    [0029]FIG. 7 is a schematic, side view of a tail transfer apparatus having a rope conveyor. 
     
    
       [0030]    Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate at least one preferred embodiment of the invention, in one form, and such exemplifications are not to be construed as limiting the scope of the invention in any manner.  
       DETAILED DESCRIPTION OF THE INVENTION  
       [0031]    [0031]FIG. 1 reveals a vacuum belt conveyor  8  which is used to transport a moving web, preferably a threading tail  9 , specifically from last drying cylinder  6  of a paper making machine, for example, to a multi-roll calender  7 . As is known, threading tail  9  is part of a moving web (for example, a paper or board web). It is used to thread the web into the paper making or paper converting machine. Before the threading operation, severed web  9   a  runs downward as indicated (FIGS. 1 and 2), being guided by a machine-width doctor  18  from cylinder  6  into a broke chest (not illustrated).  
         [0032]    Vacuum belt conveyor  8  includes an air-permeable, endless conveyor belt  10 , which runs over two rollers  11 ,  12  and a suction box or vacuum box  15 . Rollers  11 ,  12  are arranged such that they can rotate in holders (not illustrated) which are fixed to suction box  15 . One of rollers  11 ,  12  is provided with a drive, not illustrated. Indicated schematically is a vacuum source  17  for producing vacuum in suction box  15 .  
         [0033]    The conveying run of conveyor belt  10 , which runs in the web running direction, is the upper run in the present case; a converse arrangement is likewise possible. A suction box  15  has a top plate  16 , in which slots (or similar openings) are provided. The conveying run of air-permeable conveyor belt  10  slides on plate  16 . As a result, threading tail  9  is sucked onto conveyor belt  10  and transported thereby. For the further guidance of tail  9  into calender  7 , a nose shoe  50 , as it is known, and a pivotable guide plate  63  (which are known from EP 1 076 130) are provided at the outlet end of conveyor  8 . Following a successful threading procedure, tail  9  is widened in a known manner; and the complete web, designated by  9 ′ in FIGS. 1 and 2, then runs from cylinder  6  over paper guide rolls  13  and  14  onto uppermost roll  7 ′ of calender  7 . Suction box  15  is formed as an elongated body. Other designs which, for example, have an internal apparatus for producing a vacuum on the conveying run of belt  10 , can likewise be used.  
         [0034]    Provided in the inlet region of belt conveyor  8  is a transfer subassembly  20 . Transfer subassembly  20  is a tail transfer apparatus according to the invention. Transfer subassembly  20  includes a pneumatic guide plate  22 ; a low-pressure chamber  24 , which is connected via a line  25  to a compressed-air source  26 ; and a tail severing device  21  in the form of two edge nozzles. In operation, each edge nozzle  21  is arranged in one of the edge regions of tail  9  (see FIG. 2A). Each edge nozzle  21  is suitable for ejecting a high-energy air jet onto outer surface  6   a  of cylinder  6  that outputs the web. This jet achieves the situation where tail  9  running downwards is separated from cylinder outer surface  6   a  and, at the same time, tail  9  is severed transversely. From this point on, tail  9  runs with a new tail start over guide plate  22  to conveyor belt  10  and, with the latter, in the direction of calender  7 .  
         [0035]    As can be seen from FIG. 2A, width b (order of magnitude 0.2 m) of tail  9  is only a fraction of the usual width of paper web  9 ′ produced or to be converted. It goes without saying that the working width of entire web conveying apparatus  20  is matched to tail width b. However, it is also conceivable to design transfer apparatus  20  according to the invention to be as wide as the machine in a relatively narrow paper converting machine.  
         [0036]    [0036]FIG. 2 reveals that transfer subassembly  20  is supported on a rail  30  that is connected to suction box  15  and specifically so by a support  31  which can be displaced on rail  30  and by a pivoting lever  32 . As a result, transfer subassembly  20  can optionally assume an operating position, illustrated by solid lines, or a rest position, which is illustrated by dash-dotted lines in FIG. 2. In the operating position, distance a (see FIG. 3) between edge nozzles  21  and cylinder outer surface  6   a  is only a few millimeters. In addition, guide plate  22  is inclined with respect to belt conveyor  8 . By using this configuration, two outcomes are facilitated:  
         [0037]    1. The conveying run of conveyor belt  10  runs rather close along the normal running path of paper web  9 ′ between guide rolls  13  and  14 . This running path often rises upwards, as illustrated in FIG. 1, but in other cases may be approximately horizontal; and  
         [0038]    2. At the same time, it is advantageous for the point at which edge nozzles  21  separate tail  9  from cylinder outer surface  6   a  to be located rather far above the inlet region of belt conveyor  8  (i.e., in the region between cylinder  6  and paper guide roll  13 ). The tail separation position is determined, inter alia, by the desired position of dryer-fabric guide roll  5  following cylinder  6  (FIG. 1).  
         [0039]    In the rest position of transfer subassembly  20 , guide plate  22  lies approximately parallel to belt conveyor  8 . Here, the distance between cylinder outer surface  6   a  and edge nozzles  21  is many times greater than in the operating position. If required, transfer subassembly  20  can also be placed temporarily in a central, intermediate position provided between the rest and operating positions. In addition, a pivoting device, not illustrated, can be provided in order to pivot the entire apparatus (belt conveyor  8  with transfer subassembly  20 ) out of the region of the machine.  
         [0040]    As illustrated, edge nozzles  21  are preferably fixed immovably in transfer subassembly  20 . However, it is also conceivable for edge nozzles  21  to be movable relative to guide plate  22 .  
         [0041]    In order that edge nozzles  21  are capable of ejecting the required brief high-energy air jets, the following, by way of example, is provided: transfer subassembly  20  includes a high-pressure chamber  34 , to which both edge nozzles  21  are connected (FIGS. 2 and 3). High-pressure chamber  34  can be connected via a high-pressure line  36  to a high-pressure source  35 , producing compressed air having a pressure of about 5 to 15 bar (preferably about 7 to 10 bar). Provided in line  36  is a control valve  23  which, by of a timer signal carried by line  38 , can be opened briefly (for example, for 0.05 to 0.5 seconds). It is important that edge nozzles  21  eject the high-energy air jet only briefly, in order that the new start of tail  9  runs onward as far as possible without damage. In order to shorten the ejection time still further, each edge nozzle  21  can be assigned its own control valve  23  (FIG. 2A). As an alternative to FIGS. 2 and 3, edge nozzles  21  can form with each other a C-shaped tubular piece  40  or  41  into which high-pressure line  36  opens, as shown in FIGS. 4, 5. If a particularly high air outlet velocity (for example, ultrasonic velocity) is needed at edge nozzles  21 , it is possible to design edge nozzles  21  as Laval nozzles  21 A, as shown in FIG. 6.  
         [0042]    According to FIG. 3, transfer subassembly  20  includes high-pressure chamber  34 , formed so as to have a rectangular hollow profile, and guide plate  22  which, at  42  and possibly at  42   a,  has at least one step, and which at  43  is fixed in a stepped manner to high-pressure chamber  34 . Guide plate  22  and high-pressure chamber  34 , together with other walls  45 ,  46 , bound low-pressure chamber  24 , already mentioned. On step  42  (and possibly on step  42   a ) there is a row of blower openings  44 , which extend transversely over plate  22  and through which the air flows out of chamber  24 . At step  43 , additional blower openings  44  are provided on high-pressure chamber  34  and are configured to eject high-energy air jets briefly at the same time as edge nozzles  21 . All blower openings  44  produce air streams which guide tail  9  along guide plates  22  in the direction of belt conveyor  8 . The number of steps  42 ,  42   a  and  43  can be greater than or less than shown in the drawing.  
         [0043]    Wall  45 , running approximately parallel to outer surface  6   a , can have an extension which extends downwards, in order to guide severed part  9   a  of tail  9  downwards. Here, too, if necessary, a step  48  with blower openings  44  can be provided.  
         [0044]    A further special feature is that guide plate  22  has an air guide channel  49  at its end on the outlet side thereof, close to the conveying run of belt  10 . Air guide channel  49  is curved in the direction opposite to the running direction of the conveying run. The effect of such curvature has already been described further above. In further refinement (illustrated by dash-dotted lines), a resilient seal  60  slightly touching belt  10  can be provided.  
         [0045]    According to FIG. 4, high-pressure chamber  34   a  is configured in such a way, including C-shaped tubular piece  40  (which forms edge nozzles  21 ), that blower openings  44  which are active at the same time as edge nozzles  21  are positioned at a shortest possible distance a from cylinder outer surface  6   a.    
         [0046]    [0046]FIG. 5 shows a very advantageous further development: at the infeed end of transfer subassembly  20 ′ there is a Coanda nozzle  50 ,  51  with the following features: by use of a rounded edge of nose shoe  50  and thereby using the Coanda effect, an air stream led upwards from blower openings  51  is deflected in the direction of guide plate  22 . As a result, in the region of rounded edge  50 , a negative pressure zone is produced, which increases the security of the start of the transfer of tail  9  still further. In addition, within guide plate  22 , air can be supplied by at least one Coanda nozzle  52 , in order to produce a negative pressure zone. By such at least one Coanda nozzle  52 , tail  9  is supplied to belt  10  in a flat state, without any risk of fluttering.  
         [0047]    [0047]FIG. 7 shows that a tail transfer apparatus  20 ″ according to the invention, including edge nozzles  21  and a pneumatic guide plate  22 , can also be used to transfer a tail  9  separated from a cylinder outer surface  6   a  to another transport apparatus, e.g., to a rope guidance system  70 , instead of to a belt conveyor  8 . Illustrated schematically are two ropes  71  and  72  which run towards a roll  75  (in each case, over a rope pulley  73 ,  74 ) and there form a rope pinch, thereat gripping incoming tail  9  in order to transport tail  9  onwards together.  
         [0048]    Here, too, provision is made for edge nozzles  21  to eject a brief high-energy air jet, in order to separate tail  9  from cylinder outer  6   a  and, at the same time, to sever tail  9  transversely, so that a new tail start is supplied to rope guidance system  70  without forming a double tail. Double arrow  69  indicates that transfer apparatus  20 ″ can be displaced to and fro between an operating and a rest position, in a manner similar to that described above with respect to FIG. 2.  
         [0049]    While this invention has been described as having a preferred design, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.