Abstract:
Described herein is a device for splicing the free end of a strip of web material to a homologous strip of web material being supplied. The device includes a first moving element and a second moving element, each of which is able to function alternatively as retention structure for the aforesaid free end and as guiding structure for the web of material being supplied. The moving elements are, at least in part, translatable with respect to one another for connecting the aforesaid free end to the web of material being supplied, performing the operation of splicing. The first moving element and the second moving element are selectively orientable between a position of opening, in which the moving element has a gripping formation, preferably of the negative-pressure type, exposed to receive the free end, and a position of closing, in which the gripping formation faces the other moving element of the device to allow the aforesaid free end to connect to the web being supplied.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims priority from Italian Patent Application No. TO2005A000823 filed on Nov. 21, 2005, the entire disclosure of which is incorporated herein by reference.  
       FIELD OF THE INVENTION  
       [0002]     The present invention relates to devices for splicing web material. The invention has been developed with particular attention paid to its possible use in the field of plants for the production of hygienic-sanitary products.  
       BACKGROUND OF THE INVENTION  
       [0003]     In the sector of hygienic-sanitary products (and also in other sectors of the art, such as, for example, the automatic-packaging sector) there commonly find application unwinding devices for supplying web material, equipped with splicing systems (the so-called “splicers”), which enable joining to a web being supplied from a reel that is running out one end of a web of a new reel. The connection is usually made adhesively (for example, with a bi-adhesive tape), and the operation of splicing is performed by cutting the old web immediately after the join so as to reduce to a minimum the length of the “trailing end” that the old web draws along with it (or “overlap”). The operation is performed without stopping the movement of supply of the web: the stations that use the web consequently see the unwinder as a source that supplies a web of virtually infinite length without any interruption.  
         [0004]     A splicing device of the type specified above is described in the document U.S. Pat. No. 4,157,934, which is used as model for the preamble of claim  1 .  
         [0005]     Albeit having encountered a considerable success over the years, this solution is not free from drawbacks in use.  
         [0006]     The corresponding device is, in fact, built as a structure that is as a whole closed both on account of problems of safety and on account of problems of the manufacturing process. In particular, the aim is to provide a structure that is very rigid, in which the distances between the blades and the counterblade that are to make the cut in the web, as well as the distances between the two pressure pads ( 50 , according to the numbering adopted in  FIG. 1  of the document U.S. Pat. No. 4,157,934), are reduced. This is done for various reasons, not the least of which is to reduce the time necessary for completing the splicing operation.  
         [0007]     In the step of pre-arrangement of the device for carrying out the splicing operation, the operator is thus forced to work in particularly critical conditions. The unwinding devices—and hence the splicing devices associated thereto—are usually mounted in the top part of the machines so as to cause the web supplied thereby to drop down from above. This arrangement is convenient for reasons of encumbrance and because it prevents the unwinder from interfering with the other parts of the machine.  
         [0008]     However, to be able to pre-arrange the device for carrying out a new splicing operation, the operator responsible finds himself having to perform a sequence of extremely inconvenient operations.  
         [0009]     Usually, after mounting the “new” reel in the unwinder (an operation that is usually performed from the ground with a small crane or hoist), the operator climbs to the top of a ladder in order to bring himself to the same height as the unwinder and, whilst he is at the top of the ladder, leaning forwards to reach over the structures for covering and protecting the machine, he must:  
         [0010]     release from the “new” reel the free end that is to be used for the splicing operation;  
         [0011]     apply on this free end (the material being usually quite soft—for example, having the consistency of toilet paper or even less) a bi-adhesive tape for a length of 300-400 mm;  
         [0012]     insert edgeways the end of the web thus adhesivized in the top slit of the splicing device, getting it to drop until it is brought down in front of the compliant contrast element that is to press the aforesaid free end against the web of the “old” reel;  
         [0013]     ensure (operating in conditions of purely visual control—for example observing the descent of the free adhesivized end of the web through a slit of Plexiglas) the exact lateral alignment of the end of the web with the web being unwound; and  
         [0014]     finally, block the aforesaid free end of web in the desired position to be able to perform the splicing operation.  
         [0015]     The latter operation is particularly inconvenient and difficult because, to be able to activate the corresponding gripping device, the operator must free one of his hands engaged in the operation of insertion and alignment of the web.  
         [0016]     The entire operation is further complicated by the fact that, whilst the device is prepared for performing the splicing operation, the machine in which the unwinding device is included continues to function. This means that the operator encounters, at a short distance from the splicing device, the “working” web, which continues to be supplied—even at a rather fast rate—by the unwinding device. In addition, he must prevent any contact with said working web, seeing that even a short and slight contact could result, on account of the fragility of the material, in an undesired tearing of the web with the consequent need to stop the machine and the corresponding work cycle.  
       OBJECT AND SUMMARY OF THE PRESENT INVENTION  
       [0017]     The object of the present invention is to provide a splicing device, which, while maintaining the unquestionable operating advantages linked to the adoption of the solution according to the known art described previously, prevents the drawbacks outlined above from arising.  
         [0018]     According to the present invention, this object is achieved thanks to a device having the characteristics referred to specifically in the ensuing claims.  
         [0019]     The claims form an integral part of the technical teaching provided herein regarding the invention. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0020]     The invention will now be described, purely by way of non-limiting example, with reference to the annexed figures of drawing, in which:  
         [0021]      FIG. 1  is a general perspective view of a device according to the invention viewed in the condition in which the device itself is in the course of pre-arrangement for performing the splicing function; and  
         [0022]     FIGS.  2  to  4  are three vertical median cross-sectional views substantially corresponding to the plane of cross section identified by the line II-II of  FIG. 1 . 
     
    
       [0023]     In particular, the cross section of  FIG. 2  corresponds exactly to the condition represented in  FIG. 1 , where the device is pre-arranged for performing the splicing function, whilst the sections of  FIGS. 3 and 4  correspond, respectively, to the closing movement that brings the device into the condition of performing the splicing operation and causes said operating position to be actually reached.  
       DETAILED DESCRIPTION OF THE INVENTION  
       [0024]     The device according to the invention, designated as a whole by  10 , is designed to operate in the framework of an unwinding device for supplying a web material to a machine that uses it—not illustrated—constituted typically by one of the workstations of a plant for the production of hygienic-sanitary products. In this connection, it should once again be recalled that, even though the invention has been developed with particular attention paid to this possible field of application, the scope of the invention itself is not in itself limited to this context.  
         [0025]     Specifically, the device  10  is to interact with two reels A and B from which the aforesaid web material, designated as a whole by W, is unwound.  
         [0026]     In the sequel of the present description, it will ideally be assumed that the reel A is a reel that is currently supplying web material to the station that uses it, and is consequently bound to run out as a result of the gradual supply of the aforesaid material.  
         [0027]     The reel B is instead a “new” reel provided with a free end B 1  that is to be connected adhesively to the web supplied by the reel A when the latter approaches the condition where it has completely run out, in such a way as to cause the reel B to take the place of the reel A during supply of the material W.  
         [0028]     The device  10  is to be set upstream of a so-called “festoon” F, basically constituted by an array of rollers on which the material W that is being supplied is wound according to a general zigzag path, the aim being to form an accumulation or store of material W that enables continuity of supply of the material W to the station that uses it at a constant rate (generally high) whilst the sections of material W located upstream of the festoon F are slowed down (virtually stopped, at least momentarily) for carrying out the operation of splicing of the free end B 1  of the “new” reel B to the trailing stretch of the “old” reel A.  
         [0029]     In the condition illustrated in the figures of the annexed plate of drawings, the reel A is the “old” reel, whilst the reel B is the “new” reel. Of course, at the subsequent splicing operation, the reel B will be the “old” reel, whilst the reel A will be the “new” reel.  
         [0030]     The device  10  must hence be able to allow replacement of an “old” reel with a “new” reel in a situation in which, in the sequence of the operation of splicing, the aforesaid reels are located alternately on one and on the other side of the device  10 . For this reason, the device  10  has a general specular symmetry about a central median axis, designated by A-A′ in FIGS.  2  to  4 .  
         [0031]     The device  10  then comprises, as active elements, two moving elements  10 A,  10 B, substantially symmetrical with respect to the plane A-A′.  
         [0032]     As has already been said in the introductory part of the present description, the general criteria of operation of the device  10  are to be deemed substantially similar to those of the device described in the document U.S. Pat. No. 4,157,934. The general criteria of operation of such a device are hence to be deemed known, and consequently such as not to require any detailed description herein.  
         [0033]     In particular, the ensuing description aims at describing the structure of operation of the device  10 , with specific reference to achieving pre-arrangement for the operation of splicing/reel change illustrated in  FIG. 4 . Starting from this position, the action of splicing and cutting of the trailing end of the “old” reel (in the present case, the reel A) is performed according to modalities substantially similar to the ones illustrated in the document U.S. Pat. No. 4,157,934 and will consequently not be illustrated in detail herein.  
         [0034]     In general, the device  10  comprises a supporting structure with a robust frame  11 , comprising a pair of side plates  12  connected by one or more cross members  14  and with an as a whole hollow central portion that defines what can be approximately defined as a sort of central slit, through which the web material W coming from the reels A and B can be made to pass and drop downwards in the direction of the festoon F.  
         [0035]     One of the aforesaid cross members carries at the top an insert made of hard metal, designated by  140 , having a cross section shaped like an isosceles trapezium, with the major base facing upwards. As will be explained in greater detail in what follows, the insert  140  is to function as counterblade in the operation of cutting of the “trailing end” of the web of the old reel (in the case illustrated here, the reel A).  
         [0036]     Between the two plates  12  there likewise extend (in positions roughly specular with respect to the central median plane A-A′, as the vast majority of the elements described in what follows), two shafts or pins  15 , mounted about which so that they can turn are the two moving elements  10 A and  10 B that carry the active elements of the device  10 .  
         [0037]     In particular, each of the moving elements  10 A,  10 B carries a respective roller  16 , which is situated in general in the top part of the device  10  and is to function as entraining roller for the material W that is wound off the reel A or B.  
         [0038]     In a position roughly opposite to the roller  16 , each moving element  10 A,  10 B then carries a bar  18 , which extends through the structure of the device  10  (see in particular the perspective view of  FIG. 1 ) and has a general openworked structure, being provided with openings constituted, for example, by an array of slits designated by  20  (see once again the perspective view of  FIG. 1 ).  
         [0039]     Each bar  18  is to function as contrast formation capable of withholding on itself the free end B 1  of the “new” reel that is pre-arranged for performing the operation of splicing and reel change.  
         [0040]     For this purpose, provided underneath the bar  18  is a chamber  20 , which usually has an elongated shape and is possibly split up into a number of compartments, roughly co-extensive with the bar  18 . The chamber  20  comes under a pneumatic line—not explicitly visible in the drawings, but of a known type—, which enables selective creation within the chamber  22  of a level of subatmospheric pressure, i.e., a level of “vacuum”.  
         [0041]     In this way, the free end B 1  of the “new” reel B can be applied on the device  10  and withheld in a precise position, whilst a length of bi-adhesive tape T, which is to enable splicing to the web being wound off the “old” reel A, is applied on said free end B 1 , or—in any case (i.e., even when the length of web T has already been applied previously)—whilst the operator removes the strip of anti-adherent material (siliconized paper) set for protection of the face of the bi-adhesive length opposite to the web W.  
         [0042]     Provided in a position roughly set between the roller  16  and the bar  18  is a compliant contrast element  24  (for example, with spring loading), which is to keep gripped against the cross member that carries the counterblade  140  the trailing end of the web of the “new” reel whilst the latter is prepared and is awaiting reel change.  
         [0043]     Located above the compliant contrast element  24 —i.e., in an intermediate position between the compliant contrast element  24  and the roller  16 —is then a blade  26 , which is to carry out (according to the same modalities as those described in U.S. Pat. No. 4,157,934) the function of cutting the “trailing end” of the old reel on which splicing of the free end of the “new” reel has just been performed.  
         [0044]     According to a preferential characteristic of the solution illustrated herein, each of the blades  26  has a trapezoidal shape, in the sense that its front cutting edge  26   a  does not run parallel to the counterblade  140  but, instead, has a rectilinear conformation inclined at least by a small fraction of degree with respect to the counterblade  140 , with the cutting edge constantly interfering with the counterblade  140 . This angled conformation of the cutting edge  26   a  of the blades  26  means that the movement of gripping between each blade  26  and the respective side of the counterblade  140  performs, on the trailing end of the web of the “old” reel, a shearing action that starts on one side of the web and then runs transversely through the web that is being cut.  
         [0045]     This cutting modality, and in particular the presence of the counterblade  140 , is especially advantageous when it is necessary to operate on very fibrous materials, such as non-woven fabrics or absorbent materials (e.g., the so-called “acquisition layers”).  
         [0046]     The relative arrangement of the parts illustrated in the drawings corresponds, on the other hand, to a preferred embodiment of the solution described herein. Persons skilled in the sector will, however, readily appreciate that this arrangement, albeit preferred, is in no way imperative in the sense that, for example (and it is emphasized that this is just one example of different possible variants) the blade  26  could find itself in a position set between the compliant contrast element  24  and the plate  18 .  
         [0047]     An important characteristic of the solution described herein lies in the fact that the two moving elements  10 A,  10 B are not mounted in a position fixed with respect to the frame of the device  10  but are instead each able to be selectively oriented between a position of “closing” and a position of opening, which is to be used for pre-arranging either one or the other moving element for performing the operation of splicing.  
         [0048]     For immediate reference:  
         [0049]     in the perspective view of  FIG. 1 , the moving element  10 A (in the foreground) is in a position of opening, whilst the moving element  10 B (in the background) is in a position of closing, a similar arrangement being reproduced in the cross-sectional view of  FIG. 2 ;  
         [0050]      FIG. 3  illustrates the gradual movement of turning-over of the moving element  10 A from the position of opening to the position of closing, i.e., the position in which the moving element  10 B is found; and  
         [0051]     in the cross-sectional view of  FIG. 4  both of the moving elements  10 A,  10 B are in the closing position.  
         [0052]     In the condition of normal operation of the device, i.e., whilst the material W is supplied towards the festoon F from a reel (assume, for example, the reel A, with reference to the situation illustrated in the drawings), with said reel still far from the condition where it is about to run out, the device  10  is kept in a closing condition.  
         [0053]     When the condition where the reel that is currently supplying the web W runs out is approached (a condition that can be detected by an operator responsible for control, or else that is signalled automatically by a sensor—of a known type—for detecting that the reel has run out), the operator intervenes on the device  10  bringing the moving element to which the “new” reel is associated (in the case in point, the reel B) into the opening position, represented in  FIGS. 1 and 2 .  
         [0054]     At this point, the operator can proceed to picking up the free end B 1  of the “new” reel, setting it up against the bar  18  of the moving element brought into an opening position, in which (as a result of a positive command issued by the operator or else as a result of a command generated automatically—according to known criteria—following upon the movement of opening of the rotary element) the “vacuum” line that creates the subatmospheric pressure within the chamber  22  has been activated.  
         [0055]     At this point, through the openings  20  of the bar  18  a suction mechanism is provided, which enables precise positioning of the free end B 1  on the bar  18  with the consequent possibility, by the operator, of releasing the aforesaid free end, so freeing both of his hands. The aforesaid free end B 1  is kept on the moving element  10 A by the action of the vacuum (subatmospheric pressure) generated underneath the bar  18 .  
         [0056]     At this point, the operator is free to proceed to a series of operations.  
         [0057]     Said operations can comprise, for example, positioning of the length of bi-adhesive tape T on the free end B 1  of the web of the new reel.  
         [0058]     This operation may, on the other hand, already have been performed previously by the operator by applying the length T of bi-adhesive tape on the free end of the reel B at the moment when this was taken up and moved away from the outer surface of the reel B.  
         [0059]     In any case, after setting the free end B 1  of the reel B on the bar  18 , the operator can remove the strip of anti-adhesive material (typically siliconized paper) that normally protects the surface of the length T opposite to the surface that has been made to adhere to the free end B 1  of the web of the reel B.  
         [0060]     In this connection, the aforesaid protective strip usually constitutes a sufficiently rigid element that facilitates the operations of positioning and centring of the web of the “new” reel: it is in fact evident that it would be desirable to connect the web of the “new” reel to the web of the “old” reel in a centred position, i.e., without giving rise to lateral displacements of the web.  
         [0061]     It will likewise be appreciated that the solution described herein is conveniently usable also for materials W having characteristics of permeability to air (for example, perforated topsheets, or webs of non-woven fabric with a particularly sparse mesh), in regard to which an action of vacuum or suction pressure could prove insufficiently effective and reliable. The length of bi-adhesive tape T is in fact able to render the free end of the web B sufficiently compact and impermeable to air to enable a firm action of gripping by vacuum or negative-pressure.  
         [0062]     Once the free end B 1  of the web of the new reel has been properly positioned, the operator brings the moving element on which he has intervened (the moving element  10 A, in the example illustrated herein) back into position, turning it about the respective shaft  15  until it is brought back into the closing condition.  
         [0063]     As has already been said, the cross-sectional view of  FIG. 3  illustrates an intermediate step of the aforesaid movement of turning-over about the shaft  15  (which may be of the fixed type or else be free to turn according to different design choices) until the closing position represented in  FIG. 4  is reached. Usually, when said closing position is reached, this is accompanied by deactivation (preferably controlled automatically) of the line of the vacuum that applies subatmospheric pressure to the chamber  22  of the gripping bar  18 . In said conditions, in fact, the free end B 1  is withheld within the device by the mechanical-gripping system, i.e., by the compliant contrast element  24  that grips the web against the plate  18 , thus withholding the aforesaid free end in position.  
         [0064]     This process continues up to the moment when (according to the modalities that can be inferred from the document U.S. Pat. No. 4,157,934) the moving element up against which the web of the “old” reel (in the present case the moving element  10 B) is currently being unwound advances towards the other moving element (in the present case, the moving element  10 B) on which the free end B 1  of the “new” reel is positioned.  
         [0065]     The aforesaid movement of advance (which takes place on guide formations and is controlled by pneumatic cylinders, according to criteria in themselves known) brings the web of the “old” reel up against the length of bi-adhesive tape T set on the free end B 1  of the “new” reel.  
         [0066]     In this way, the free end B 1  of the “new” reel is spliced to the web of the “old” reel and is thus drawn towards the festoon F, which in the meantime has been activated so as to decrease (and virtually nullify) the rate of advance of the stretch of web from the device  10  in such a way that the operation of splicing can be carried out without applying appreciable stresses on the web itself.  
         [0067]     At the same time, the movement of advance of the moving element  10 B causes the respective blade  26  to advance with respect to the counterblade  140  and to cut (with the shearing action described previously) the web of the “old” reel: the cut is made in a stretch of the web of the old reel which—in the direction of advance—is located immediately after the stretch that has been made to adhere against the length of web T carried by the “new” reel.  
         [0068]     The web of the “old” reel is thus isolated with respect to the web (now supplied by the “new” reel) that drops towards the festoon F, leaving as residue just a short “trailing end”, which can possibly be discarded at the level of subsequent treatment operations. The “old” reel, which has run out, can thus be removed from the unwinder, to be replaced by a full reel that is to constitute the “new” reel in a subsequent operation of splicing and reel change. The device  10  will be pre-arranged for carrying out this subsequent operation by acting on the moving element  10 A, which will be opened and then reclosed by performing a sequence of operations altogether similar to the one described previously, with the roles of the reels A and B and, respectively, of the moving elements  10 A and  10 B, reversed.  
         [0069]     As will be appreciated more clearly from the cross-sectional views of FIGS.  2  to  4 , the movement of orientation of the moving elements  10 A and  10 B between the positions of opening and closing is obtained about the shafts  15  under the control of a mechanism with oscillating arm, which is identical for both of the moving elements  10 A and  10 B, and comprises:  
         [0070]     a rotary actuator  30 , which is to be controlled in rotation by the operator (directly by hand or using a tool) about an axis X 30  parallel to the shafts  15 ;  
         [0071]     an arm  32 , which is drawn by the actuator  30  in a movement of slewing about the axis X 30  and carries at its distal end a follower element  34  such as, for example, a follower roller; and  
         [0072]     a cavity  36  for sliding of the follower element  34 , such as a rectilinear slit  36  (possibly open at one end) made in the body of the moving element  10 A or  10 B.  
         [0073]     As will be appreciated more clearly from the comparison between  FIGS. 2 and 4 , the end positions of the aforesaid slewing movement (which has an amplitude of 90°) correspond to dead-centre conditions, in which the follower roller  34  is located at the end of the slit  36  more distant from the axis of the shaft  15  about which the moving element  10 A turns. At the same time, the intermediate position of turning-over represented in  FIG. 3  causes the follower roller  34  to advance towards the end of the slit  36  closer to the axis of the shaft  15  about which the moving element  10 A turns.  
         [0074]     In other words, the lever ratio of the mechanism (considered from the standpoint of the moving element) is most unfavourable at the two end positions (closing and opening).  
         [0075]     Thanks to the mechanism described, in which at least one of the end positions—and preferably both of them—are dead-centre positions, the movement of opening and closing of the device  10  is convenient and “smooth” and, at the same time, the end positions (opening and closing) are in any case intrinsically stable, so that—for example—the operator does not run the risk of the moving element in the opening condition, on which he is applying the free end of the web, accidentally reclosing.  
         [0076]     Equally advantageous, on the basis of the experiments conducted by the present applicant, is the intrinsic stability of the closing position, which, in combination with the shearing mechanism with which the blades  26  co-operate with the counterblade  140 , renders altogether reliable and precise the operation of cutting of the trailing end of the old reel, in this way overcoming a deep-rooted prejudice against the possibility of doing without completely rigid and fixed structures for providing splicing devices of the type described herein.  
         [0077]     A further degree of stability of the aforesaid positions of opening and/or closing can be achieved by setting between the moving elements  10 A and  10 B and the fixed frame of the device  10  spring-loaded pawls  38 , which block the movement of orientation of the moving elements  10 A and  10 B and must be brought into a position of release by the operator in order to open and/or close the device.  
         [0078]     Of course, without prejudice to the principle of the invention, the details of construction and the embodiments may vary widely with respect to what is described and illustrated herein, without thereby departing from the scope of the present invention, as defined by the annexed claims.