Abstract:
A machine ( 1 ) for transferring fluids to a moving web ( 3 ), comprises: a spreading roller ( 2 ) by which the fluids are spread and which is configured to come into contact with the moving web ( 3 ); a plurality of distribution rollers ( 5 a- 5 e) on which the web ( 3 ), which is subject to tensioning, is made to run; and a transfer system ( 8 ) for transferring fluids to the spreading roller ( 2 ); the plurality of distribution rollers ( 5   a - 5   e ) is rotatably pivoted on fixed pins relative to the machine ( 1 ) and the spreading roller ( 2 ) is slidably constrained to the machine. The invention also relates to a method for transferring fluids to a web by means of the machine.

Description:
TECHNICAL FIELD 
       [0001]    This invention addresses the sector of machines for transferring fluids to a web. More in detail, the invention addresses the sector of machines for transferring adhesive substances to a moving web. 
         [0002]    This invention also relates to a method for transferring fluids to a web and describes a computer program designed to make the machine of the invention implement the method described. 
       BACKGROUND ART 
       [0003]    In prior art machines for transferring fluids to a moving web, a spreading roller is usually used which operates in contact with the web in order to transfer the fluid thereto. 
         [0004]    In particular, for transferring paint, the spreading roller may be an “anilox” roller (typically made of ferrous—steel—or ceramic material) which is soaked with paint. A scraper blade, known as doctor blade, removes the excess paint from the roller. Typically, an anilox roller has a plurality of cells formed on the surface of it which are used for printing purposes. The smaller the cells are in size, the finer the detail of the paint transferred to the web. 
         [0005]    In machines known up to the present, there is a tensioned web to which the spreading roller distributes the glue or paint. In these machines, the doctor blade is also used to transfer the glue or paint collected by a receptacle on the spreading roller. A plurality of distribution rollers (known in Italian by the term meaning “basket”) define a path along which the web is wound and kept tensioned. The amount of glue or paint transferred is determined by the mutual position between the doctor blade and the spreading roller. 
         [0006]    More specifically, in prior art machines, the basket is movable relative to both the spreading roller and the doctor blade and it moves between a first position, or operating position, where the web is in contact with the spreading roller, and a second position, or rest position, where it is away from the spreading roller. More specifically, when the basket is at the rest position, it is possible, for example, to change the web and, obviously, the fluid (glue or paint) is not transferred. 
         [0007]    The movement of the distribution rollers, however, causes the web to stretch or lose its tension leading to operating problems such as creasing or non-uniform spreading of the fluid). 
         [0008]    This invention has for an aim to provide a machine for transferring fluids to a web and which contributes to overcoming the above mentioned disadvantages. 
         [0009]    More specifically, the aim of this invention is to provide a machine for transferring fluids to a web and which allows preventing damage to the web during the passage from the operating position to the rest position and vice versa. 
       SUMMARY OF THE INVENTION 
       [0010]    According to this invention, there is provided a machine for transferring fluids to a moving web, comprising:
       a spreading roller by which the fluids are spread and which is configured to come into contact, at least temporarily, with the moving web;   a plurality of distribution rollers on which the web, which is subject to tensioning, is made to run;   and a transfer system for transferring fluids to the spreading roller;   and wherein the plurality of distribution rollers is rotatably pivoted on fixed pins relative to the machine and wherein the spreading roller is slidably constrained to the machine.       
 
         [0015]    Advantageously, the spreading roller is an “anilox” roller and is configured for transferring both paints and adhesives to the web. 
         [0016]    Advantageously, the fluid transfer system is movable and has a doctor blade capable of adjusting the quantity of fluid transferred to the spreading roller. 
         [0017]    Advantageously, there is a pair of carriages which are movable relative to a pair of side shoulders of the machine and which are driven by respective actuating means, the spreading roller being rotatably pivoted to these carriages. 
         [0018]    Advantageously, the machine also comprises movable protection means configured to be interposed at least partially—in a use position—between the spreading roller and the web. 
         [0019]    Also provided according to the invention is a method for transferring fluids to a web comprising a step of coupling a spreading roller, forming part of a machine for transferring fluids to a web, to a moving web made to follow a path defined by a plurality of distribution rollers pivoted on the machine, and a subsequent step of moving the spreading roller away from the web without changing the position of the distribution rollers on the machine. 
         [0020]    Advantageously, the method also comprises a step of moving a doctor blade, which forms part of a fluid transfer system, relative to the spreading roller. 
         [0021]    Advantageously, the method comprises a step of unwinding and feeding the web in controlled and tensioned condition from a first drum upstream of the spreading roller and then rewinding it on a second drum downstream of the spreading roller and of the plurality of distribution rollers. 
         [0022]    Advantageously, the coupling step and the moving-away step comprise a step of driving a pair of carriages supporting the spreading roller on a gear meshed with a rack on the carriages between a first and a second limit position and a step of transmitting electrical signals from limit sensors to a data processing unit in order to stop the driving action. 
         [0023]    Advantageously, the step of moving away the spreading roller comprises a step of detecting the complete retraction thereof and a subsequent step of automatically transmitting a protection means drive signal to means for actuating a protection element such that the actuating means perform a movement by which the protection element is driven from an initial rest position where it is not interposed between the spreading roller and the web to a second protection position where it is interposed between the spreading roller and the web. 
         [0024]    Further provided according to the invention is a computer program stored on a non-volatile storage medium and capable of being run by at least one electronic processor to allow performing the steps of the method according to any of the features described above. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0025]    Further features and details of a preferred, non-limiting embodiment of the machine and method for transferring fluids to a web appear in the description which follows with reference to the accompanying drawings, in which: 
           [0026]      FIG. 1  shows a perspective view of the machine of the invention; 
           [0027]      FIG. 2  shows a lateral cross sectional view of a first operating configuration of a machine for transferring fluids to a web according to this invention; 
           [0028]      FIG. 3  shows a lateral cross sectional view of the machine of  FIG. 1  in a rest configuration; 
           [0029]      FIG. 4  shows a lateral cross sectional view of the machine of the invention in a further configuration where the protection elements are moved in order to keep a web separate from a spreading roller; and 
           [0030]      FIG. 5  shows a lateral cross sectional view of the machine of the invention in a further configuration where a spreading roller is moved. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0031]    With reference to  FIGS. 1 and 2 , the reference numeral  1  denotes in its entirety a machine for transferring fluids to a web. More in detail, the machine  1  is configured to transfer paint to a moving web and is designed to transfer not only paints but also glue from a spreading roller, also called “anilox” roller,  2  to a moving web  3  which, in use, is unwound from a first loading drum  4   a  and rewound onto a second drum  4   b . More specifically, the moving web  3  is made to slide on a plurality of distribution rollers  5   a - 5   e  which make the web follow a curvilinear path. Although the accompanying drawings show five distribution rollers, the number and specific configuration of the distribution rollers should not be viewed as limiting the invention. In the same way, the configuration of the first and second drums  4   a,    4   b  should not be viewed as limiting the invention, since other convenient assembly solutions are imaginable. The configuration of the first and second drums appearing in the accompanying drawings is therefore purely exemplary and the two drums are represented in those positions solely for completeness of illustration. 
         [0032]    The surface of the spreading roller  2  is dimpled which means, more in detail, that it has a plurality of cells adapted to contain a printing fluid or, advantageously according to this invention, a glue or adhesive substance. The smaller the cells are in size, the greater the printing resolution obtained. The size of the cells also determines the quantity of fluid transferred from the spreading roller to the moving web. The spreading roller is preferably, but not necessarily, made of steel or of ceramic material. 
         [0033]    More specifically, the machine of the invention is characterized by a spreading system, known in the jargon of the trade as “chamber doctor blade” system, where the quantity of fluid to be applied to the web is determined by the spreading roller  2  and, partly, by the clearance between the roller and the moving web. The chamber doctor blade system takes its name from a doctor blade commonly used to remove excess paint or ink from the spreading roller  2 , and which, in this invention, is advantageously also used to distribute adhesive substances. 
         [0034]    The moving web  3  is moved by the active rotation of at least one between the first drum  4   a  and the second drum  4   b.  Conveniently, if both drums  4   a ,  4   b  are actively rotated, for example by respective motors, they are provided with means for adjusting the rotational synchronism so that the moving web  3  is always kept tensioned to the optimum extent independently of the amount of it that is wound around the drum. 
         [0035]    The means for adjusting the synchronism are preferably controlled by a data processing unit installed on the machine  1  and whose purpose is to supervise all the operating steps of the machine. Conveniently, the data processing unit is electrically connected to a non-volatile storage medium containing software or firmware for managing machine operation and to user interface devices to allow displaying one or more machine operating states and entering operating commands. The data processing unit may, for example, without limiting the invention, comprise a PLC controller, but this may be technically and equivalently substituted for an electronic processor equipped with at least one general purpose processor configured to run a program which causes the machine to operate in the manner described hereinafter. Thus, the electronic processor may also be a personal computer installed outside the box or frame of the machine of this invention. 
         [0036]    A distinctive feature of the machine  1  of the invention is that the distribution rollers  5 , although they rotate on respective pins, are fixedly positioned relative to a first and a second shoulder  6 ,  7  of the machine  1 . The first and second shoulders  6 ,  7  of the machine  1  are part of a mounting frame of the machine  1 . 
         [0037]    More in detail, the first and second shoulders  6 ,  7  are positioned on the left and right of the machine, respectively, and act as vertical supporting elements for a pair of carriages, described in more detail below, which act as support at least for the pin of the spreading roller  2 . Since the shoulders  6 ,  7  are in turn fixed to the rest of the frame of the machine  1 , the distribution rollers do not vary their position relative to the machine. The axes of rotation of all the distribution ropers  5   a - 5   e  and of the spreading roller are all parallel. This parallelism is very important to guarantee the absence of creases on the web  3  and to ensure that the fluid is distributed uniformly. 
         [0038]    In the machine of this invention, therefore, it is the spreading roller  2  that is movable, as is a doctor blade  8 , whose purpose is to transfer a fluid—be it an adhesive substance (glue) or a paint—from a receptacle forming part of the chamber doctor blade system to the spreading roller  2  and if necessary, to reduce the excess fluid present thereon, thus constituting a metering system for obtaining a precise quantity of fluid on the spreading roller  2 . 
         [0039]    More in detail, the machine  1  of the invention comprises a pair of carriages  10 ,  11  mounted externally of the first and second shoulder  6 ,  7 , respectively, and configured to constrain an assembly made up of the spreading roller  2  and the doctor blade  8 . More specifically, the carriages  10 ,  11 , which are of generally rectangular shape, lie in a plane substantially parallel to the plane defined by the main surface of the respective first and second shoulder  6 ,  7  and run linearly relative to the first and the second shoulder  6 ,  7 , being limited in their movement by rails made on the shoulders and being driven by a respective linear actuator  12  which, in use, is preferably, but not necessarily, embodied by a hydraulic piston. 
         [0040]    If present, limit sensors are located at the first and second shoulders in such a way as to allow identifying the position of the carriages precisely. These sensors, if present, are electrically connected to the data processing unit of the machine  1 , so that the position of the carriages can be automatically acquired. 
         [0041]    Under each carriage  10 ,  11  there is a gear  13  which is pivoted to the respective shoulder in such a way as to project outwardly from the shoulder itself. This gear meshes with a rack  14  located on the underside of each carriage and advantageously allows the carriage to move more smoothly than it would if the gear were not fitted. In effect, without the gear, the considerable distance between the two shoulders, dictated by the width of the spreading roller  2  and the weight of the assembly composed of the latter and the doctor blade  8 , would very probably lead to jerky movements. This is due partly also to the considerable length that the spreading roller  2  may have in large machines. 
         [0042]    The machine of the invention also comprises at least one protection element for protecting the spreading roller  2  and the web  3  from each other. The protection element comprises a pair of covering elements  16 ,  17  driven, in use, by respective actuating means. The first and second covering elements  16 ,  17  are both movable between a first, rest position and a second, use or safety position. In the first, rest position, they do not interfere with the transfer of fluid from the spreading roller  2  to the moving web  3 , whereas in the second, safety position, they are at least partly interposed between the spreading roller  2  and the portion of the moving web  3  in front of it, in order to protect the web from the selfsame spreading roller. In effect, under certain operating conditions, there may be air flows which would cause the moving web  3  to bend or swing to such an extent as to cause it to come into contact with the spreading roller  2  at times when there should not be any such contact (when the spreading roller  2  is at the rest position). The first and second covering elements also guarantee greater safety for the operator, in particular when loading the web into the machine, because it prevents the operator from coming into contact with the spreading roller. More in detail, the covering means comprise a first portion  16  which is above the second and which is slidable vertically and rotatable on a pin located at one end of it, and a second movable portion which, when in the safety position, is interposed between the spreading roller and the web. The movement of the second, movable or active portion  17  is determined preferably by the user entering a specific command from the user interface means connected to the data processing unit which sends a signal for moving the second active portion by driving the actuating means thereof and causing the second active portion to move from the first to the second position. A further command for returning to the working condition, on the other hand, will cause a signal for moving the covering elements to be transmitted by the data processing unit to the actuating means to return the second portion  17  to the first, rest position. Limit sensors are electrically connected to the data processing unit to indicate that the second portion  17  has stopped correctly at the respective first or second position. 
         [0043]    In use, as illustrated in  FIG. 2 , during the normal operation of the machine  1  (operating configuration), the spreading roller  2  is at a working position and is in contact with the moving web  3  to transfer to it the adhesive (glue) or paint, whose quantity depends on the surface structure of the spreading roller  2  (more in detail, on the shape and/or number of the cells on the anilox roller) and/or on the rotation speed of the spreading roper  2 . 
         [0044]    The second portion  17  of the covering elements is held in a raised position on a column  18  of the machine  1 . 
         [0045]    The machine  1  can be controlled through the user interface means to activate a rest configuration, illustrated in  FIG. 3 , where the data processing unit sends a drive signal for moving the linear actuators  12  of the carriages. Conveniently, the linear actuators are preferably hydraulic, the drive signal activates, for example, an electric/hydraulic servoactuator system connected to the linear actuators  12 . In the rest configuration, the spreading roller  2 -doctor blade  8  assembly is linearly translated towards a rear portion of the machine of the invention. When the limit sensors detect that the spreading roller  2 -doctor blade  8  assembly has correctly reached the rest position, they transmit an electric signal to the data processing unit and the machine control software activates the actuating means for lowering the second portion  17  of the covering elements. As illustrated in  FIG. 4 , only at this point is the first portion  16  of the covering elements made to move translationally so that one end of it comes to rest on one edge of the machine frame to protect the top of the spreading roller  2 . The translational movement of the first portion  16  of the covering elements may be performed automatically when the spreading roller  2 -doctor blade  8  assembly reaches the rest position or, alternatively, it may be activated by the user with a separate command. 
         [0046]    As illustrated in  FIG. 4 , the machine  1  of the invention also comprises a configuration for changing the spreading roller  2 . In this configuration, which can be conveniently activated by the user through the aforementioned user interlace means, the data processing unit activates a drive signal for moving the closed chamber doctor blade system, which is pivoted on a respective rotation pin  20 . In this configuration, the closed chamber system which comprises the doctor blade  8  is automatically rotated by respective rotation means in order to release the spreading roller  2  so it can be extracted from the machine  1 . More specifically,  FIG. 5  shows a rotation by 90° in an anticlockwise direction but this must not be considered as limiting the invention, since other equivalent solutions comprise a rotation through a different angle or a rototranslation of the closed chamber system relative to the roller. 
         [0047]    The advantages of the machine  1  of the invention are evident in light of the foregoing description. More in detail, since the spreading roller  2  is installed on an assembly which is movable independently of the plurality of distribution rollers and mounted on carriages which are not rigidly connected to the frame of the machine  1 , the spreading roller  2  is advantageously subject to less vibration. In effect, the non-rigid connection between the spreading roller and the machine frame dampens the detrimental vibrations that would otherwise be imparted to the spreading roller, thus improving the quality of fluid distribution on the web. 
         [0048]    Advantageously, also, the spreading roper  2  can be changed more quickly, which allows the machine to work more rapidly in diverse operating conditions where the spreading roller needs to be changed on account of changes in the quantity of fluid required. 
         [0049]    Advantageously, the moving web  3  follows a fixed path since the distribution roller assembly is rigidly connected to the machine. Consequently, there is less risk of sudden variations in the tensioning force applied to the web, with obvious advantages in terms of improved quality of printing or transfer of the fluids from the roller to the web. In both the rest configuration and in the use or operating configuration, the machine of the invention does not change either the path or the tension of the moving web  3 . 
         [0050]    It will be understood that the machine  1  of this invention can be modified or adapted in several ways, obvious to an expert in the trade, without thereby departing from the scope of protection offered by the accompanying claims.