Patent Publication Number: US-2022226858-A1

Title: Gluing station and method for operating such a gluing station

Description:
FIELD OF INVENTION 
     The invention relates to a gluing station for applying glue to product elements guided in a product stream. It further relates to a method of operating such a gluing station. 
     BACKGROUND OF INVENTION 
     In the manufacture of flat paper products such as envelopes, mailing bags, and similar products, or also in the manufacture of single-ply or multi-ply fiber or tissue products such as hygiene products, handkerchiefs, toilet paper, or the like, the application of glue to the products may be necessary. In the case of the manufacture of envelopes, for example, the glue is applied to the envelope flap for subsequent adhesion thereto. In the process, the glue is remoistened by the moisture in a sponge or that in saliva and is thus activated. 
     The glue is usually applied to the products by passing the product elements past a gluing station in a product stream, for example an imbricated stream. Alternatively, the glue can also be applied to staggered or individual products at specific points or in block form. The gluing station typically includes a glue application roller to which the glue is applied from a glue bath or trough by means of an upstream scoop roller and an intermediate transfer roller. The glue application roller in turn rolls on the product/product stream, transferring the glue on its surface to the product elements. 
     In the ongoing production process, the glue application roller is thus continuously glued by the gluing unit, and it then immediately releases this glue again onto the product elements guided in the product stream, for example, especially the paper. In the event of a machine stop, however, where the product stream has to be interrupted briefly or temporarily, the glue application roller is swung away from the medium, and the gluing unit and the glue application roller are also separated. In such a case, the gluing unit is usually kept in motion by a continuous motor and continuously supplied with fresh glue, while the glue application roller, on the other hand, is not moved. When the machine stops, the glue on the application roller gradually dries. This means that when the production process is resumed and the glue application roller is started up, the product flow sticks to the application roller and thus causes a disruption in the production process. 
     SUMMARY OF INVENTION 
     The invention is therefore based on the task of specifying a gluing station of the type mentioned above, with which it is possible to continue the production process and the gluing of the product elements in a particularly simple and reliable manner even after a temporary machine stop or production standstill. Furthermore, a method for operating such a gluing station is to be specified. 
     With regard to the gluing station, this task is solved according to the invention by assigning a moistening system to the glue application roller. 
     The invention is based on the consideration that the difficulty of continuing the production process after a machine standstill, which is regarded as disadvantageous, is caused in particular by the drying out of the glue which begins during the standstill of the gluing station. Particularly in the case of the remoistenable types of glue preferred for the production of envelopes, this is made even worse by the fact that the glue in the comparatively moist state in which it is usually processed in the gluing station usually has a lower adhesive strength than when it becomes increasingly dry. The drying out of the glue thus not only results in fundamentally more difficult handling, but also additionally increases the risk of a detrimental effect on the subsequent process steps due to increasing gluing. 
     However, the cleaning of the glue application roller usually required after such a stoppage, during which the glue residues have to be completely removed manually, is time-consuming and resource-intensive. In order to remedy this situation, the gluing station should be equipped to keep the residual glue on the glue application roller moist as required, so that it can be processed further without any problems once the production process has been resumed. Accordingly, a moistening system is associated with the glue application roller in the sense that the (residual) glue on the surface of the application roller can be kept moist during a downtime of the system, i.e. that the surface of the application roller can be supplied with moisture to a degree that is at least sufficient for this purpose. 
     Advantageous embodiments of the invention are the subject of the subclaims. 
     The glue application roller is preferably designed as a rubber roller. 
     With regard to common water-based glues that are particularly suitable for the advantageously intended application, namely the application of remoistenable adhesive zones on envelopes, the moistening system is advantageously designed for glue moistening with water as the moistening agent. Particularly effective and efficient moistening can be achieved by supplying the water to the roller surface in the form of a water mist or a moist air stream. Particularly preferably, the moistening system therefore comprises a water nebulizer 
     In a further preferred embodiment, the moist air flow is guided to the glue application roller close to the surface, i.e. preferably in such a way that the roller surface is acted upon particularly efficiently. 
     A particularly simple, cost-effective and reliable design of the system can be achieved in that the water nebulizer is advantageously designed as an ultrasonic atomizer, in particular with a fan, or comprises such a fan. 
     In another particularly advantageous embodiment, the guidance of the moist air is designed for particularly efficient, uniform and precise wetting of the surface of the glue application roller. For this purpose, the water nebulizer is advantageously combined with an outlet nozzle for the water mist or moist air stream, via which the water mist can be supplied to the surface of the glue application roller in a laminar flow, preferably uniformly at a suitable inflow angle. This ensures that the supplied water mist can largely adhere to the roller surface after flowing out of the outlet nozzle, so that particularly effective wetting with precipitation of the water mist on the roller surface is possible. 
     A particularly good transfer of the generated water mist to the roll surface can be achieved by the water nebulizer advantageously having a collection chamber for excess water mist in the mist outlet area. The excess moistening agent collected in this way can thus be returned directly to the roll surface, while in addition an intrinsically undesirable discharge of the moistening agent into other parts of the system can be minimized or possibly avoided altogether. 
     With regard to the method for operating a gluing station of the type mentioned, the above-mentioned task is solved in that, in the case of a product flow that is stopped, in particular temporarily, for the duration of the standstill, the glue application roller is pivoted away from the product flow and is kept rotating further, the surface of the glue application roller being moistened. 
     Alternatively or additionally, intermittent moistening of the glue application roller or intermittent or piecemeal rotation of the glue application roller can also be provided. 
     Preferably, and in an embodiment regarded as independently inventive, a water-based dextrin glue (remoistenable) is used in a gluing station of the type mentioned above. Such a glue in particular already has a comparatively strong adhesive effect when drying begins, which in particular can significantly exceed the adhesive effect in the moist state. Particularly in combination with such a glue, the intended glue moistening during the downtimes can particularly favor the subsequent, preferably almost undercutting-free continuation of the production process, since the glue remains limited in its adhesive effect due to the moistening and an undesirably strong sticking or adhering of the product parts after resumption of the process can be kept limited. 
     The advantages achieved with the invention consist in particular in the fact that the moistening system associated with the glue application roller makes it possible to achieve effective continuous moistening of the glue located on the surface of the glue application roller, so that its further processing is made possible in a particularly reliable and particularly simple and cost-saving manner, even after temporary downtimes in the production process. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       An embodiment of the invention is explained in more detail with reference to a drawing. Therein show: 
         FIG. 1  production line for manufacturing envelopes, and 
         FIG. 2  gluing station of the production line shown in  FIG. 1 . 
     
    
    
     Identical parts are marked with the same reference signs in both figures. 
     DETAILED DESCRIPTION 
     The production line  1  shown in  FIG. 1  is intended for the production of letter bags, envelopes  2  and/or mailing bags, each provided with a closure flap with adhesive zones. The production line  1  comprises several stations of conventional design, of which only parts of a bottom flap folding station  4  and a side flap folding station  6  are shown schematically in  FIG. 1 . From the side flap folding station  6 , the envelopes  2  (and the like) enter a staggering station  8  with a staggering wheel  10 . With the aid of the staggering wheel  10 , the individually arriving products, envelopes  2  or mailing bags, are pushed together so that they overlap one another and are then transported further into a gluing or gluing station  20 , forming a product stream  12 , in the example a shingled stream. In the gluing station  20 , a glue or adhesive  22  is applied to the insides of the flaps of the envelopes  2  or mailing pockets. Products are then pulled apart slightly so that the glue does not stick the products together. The adhesive  22  forming an adhesive zone is then dried in the drying section for further processing. 
     The gluing station  20  is shown enlarged in  FIG. 2 . It includes a glue trough  28  in which the glue or adhesive  22  is held ready for processing. A scoop roller  30  is partially immersed in the glue  22  held in the glue trough  28 , so that when the scoop roller  30  rotates about its longitudinal axis, a partial amount of the glue  22  adheres to the surface and is thus conveyed out of the glue trough  28 . Rolling on the surface of the scoop roller  30  is a transfer roller  32 , to which the glue  22  adhering to the surface of the scoop roller  30  is transferred. A glue application roller  34  in the form of a rubber roller can be pivoted onto the transfer roller  32  and, when pivoted in, also rolls on the product stream  12  formed by the product elements, in this example the envelopes  2 . The product stream  12  is thereby guided past the gluing station  20  in the transport direction indicated by the arrow  36 , so that the glue  22  located on the surface of the glue application roller  34  is transferred to the desired positions of the product elements or envelopes  2 . 
     In the event of a machine or production stop, in which the further transport of the product stream  12  in the transport direction is temporarily interrupted, for example as a result of a production error, a process malfunction or machine set-up work, the glue application roller  34  is temporarily swung out from the working position shown in  FIG. 2  and separated from the transfer roller. In this case, the so-called gluing unit, i.e. the ensemble of scoop roller  30  and transfer roller  32 , is kept in motion as required or unchanged by a continuation motor not shown in greater detail, and is continuously supplied with fresh glue  22 , so that here drying of the glue  22  is prevented by the continuous material exchange. 
     The glue application station  20  is now specifically designed so that, in such a state of temporary production stop, the drying of the glue  22  located on the surface of the glue application roller  34  is also prevented in a particularly simple and reliable manner, so that, after termination of the temporary production stop, a particularly efficient and simple continuation or resumption of the production process can take place. For this purpose, during the production stop, an as-needed, preferably continuous, uniform moistening of the glue  22  located on the surface of the rotating glue application roller  34  is provided. To make this possible, the gluing station  20  is provided with a moistening system  38  associated with the glue application roller  34 . 
     With regard to its components and their positioning within the gluing station  20 , the moistening system  38  is thereby quite preferably designed for a demand-oriented supply of a moistening agent, in the embodiment example water, to the surface of the glue application roller  34 . In the embodiment example, this supply is to take place as a water mist according to a particularly preferred embodiment of the invention, in order to ensure a resource-saving and yet very efficient use of the moistening agent. For this purpose, the humidification system  38  comprises a water nebulizer  40 . 
     In this case, the water nebulizer  40  with its outlet nozzle  44  is suitable with regard to the intended mode of operation and is positioned close to the surface of the glue application roller  34 , so that an efficient supply of the generated water mist to the glue application roller  34  is possible. In the particularly preferred embodiment shown, the water nebulizer  40  comprises an ultrasonic atomizer  42  as the actual nebulizing element. 
     In order to enable the preferred desired delivery of the generated water mist to the surface of the glue application roller  34  in laminar flow, the moistening system  38  is also provided with or combined with a suitably selected and dimensioned outlet nozzle  44  for the water mist. The water mist generated by the ultrasonic atomizer  42  is transported to the outlet nozzle  44  by a blower  48  and a suitably selected hose  50 . 
     In addition, a collection chamber  46  for excess water mist is arranged in the mist outlet area downstream of the outlet nozzle  44 . This serves to prevent any water mist that may bounce off the surface of the glue application roller  34  from escaping directly into the machine environment at the outlet of the nozzle  44 , but to allow it to remain as far as possible on the glue application roller  34  or on the glue  22 . 
     During operation of the production line  1  or of the gluing station  20 , in the event of a stopped product flow  12 , the glue application roller  34  is pivoted away from the product flow  12  and from the transfer roller  32  for the duration of the standstill and is further kept in rotation, the surface of the glue application roller  34  being moistened. When the production line  1  is restarted, the glue application roller  34  is preferably first glued for a few revolutions before it is pivoted towards the transport section. This is to ensure optimum glue consistency 
     In the embodiment and in a particularly preferred embodiment, a water-based, remoistenable dextrin glue is used as the glue  22 . When drying begins, this exhibits a significantly increased adhesive effect compared to the still liquid state. It can also be reactivated or removed from non-absorbent surfaces by adding water when drying begins. Its viscosity is preferably approx. 4450 mPA*s, its solids content approx. 67% and its density 1.16 g/ml. 
     LIST OF REFERENCE SIGNS 
     
         
         
           
               1  Production plant 
               2  Envelopes 
               4  Floor flap folding station 
               6  Side flap folding station 
               8  Relay station 
               10  Relay wheel 
               12  Product flow 
               20  Elimate station 
               22  Glue, adhesive 
               28  Glue tub 
               30  Scoop roller 
               32  Transfer roller 
               34  Glue application roller 
               36  Arrow 
               38  Humidification system 
               40  Water nebulizer 
               42  Ultrasonic atomizer 
               44  Outlet nozzle 
               46  Collecting chamber 
               48  Fan 
               50  Hose