Patent Publication Number: US-2003234314-A1

Title: Rewinding machine with flanks carrying mating centers moving along a closed path

Description:
TECHNICAL FIELD  
       [0001] The invention relates to a rewinding machine for the production of web reels. More in detail, the invention relates to a rewinding machine of the type comprising:  
       [0002] at least a first and a second winding cylinder, whose axes are parallel, defining a winding cradle in which said reels of web are formed, and  
       [0003] mating centers for engaging and withholding winding mandrels on which the reels are formed in the winding cradle.  
       [0004] The invention also relates to a method for the production of reels of web.  
       STATE OF THE ART  
       [0005] Operations concerning winding or rewinding web are required in the sector of non-woven processing, e.g. in the production of reels of semifinished materials intended for the production of sanitary towels, diapers and the like, and also in the production of paper, e.g. for the production of rolls of toilet paper, kitchen paper or similar, for the production of reels for supplying folding machines for the production of napkins, paper handkerchiefs and similar disposable products.  
       [0006] The web production process is continuous and the web is wound on large diameter parent reels. These reels are later unreeled and the web is rewound on smaller diameters reels or rolls. For some applications, the web is cut longitudinally and continuously and wound on winding cores, which can be made of cardboard, plastic or other suitable material, the core being fitted and aligned on a winding mandrel. In this way, a plurality of reels is produced with one single rewinding cycle, each reel being less high than the initial web width and, if required, the reels can also be of different heights. The winding mandrel on which the winding cores are fitted is expandable, e.g. pneumatically or in any other equivalent way, to secure the winding cores onto it in the required positions. The various tubular cores—whose reciprocal axial length may be either variable or different—receive corresponding strips of web obtained by longitudinally cutting the web from the parent reel.  
       [0007] The rolls or reels are developed in sequence. The finished reel is unloaded from the winding cradle, e.g. formed by two winding rollers arranged side by side, and replaced with a new winding mandrel onto which the winding cores were previously secured.  
       [0008] A rewinding machine of this type is described in EP-A-0747308. Another example of rewinding machine of this type is described in EP-A-1070675. Additional examples of peripheral rewinding machine of the start-stop type, i.e. in which the supply of web is temporarily interrupted to replace the completed reel with another winding mandrel, are described in GB-A-2268476, DE-C-3836367, EP-A-0640544.  
       [0009] These rewinding machines must be capable of winding reels or rolls whose dimensions may be large at considerably high winding speeds. Typically, the web is fed at speeds exceeding 1000 meters per minute, also in the order of 2000 meters per minute. The production rate is consequently relatively high. The phase in which the finished reel or roll is exchanged with a new winding mandrel is the phase of the winding cycle which mostly slows down the overall production rate. In this phase, in these machines, the feeding speed of the web is considerable reduced and in certain cases feeding is stopped for a short time. The machine gradually returns to running speed after unloading the reel and introducing the new winding mandrel.  
       [0010] Reducing the time required for the exchange operation is consequently crucial for reducing the winding cycle time.  
       OBJECTS AND SUMMARY OF THE INVENTION  
       [0011] Object of the invention is to provide a rewinding machine of the aforesaid type in which the rewinding cycle speed can be increased and particularly in which the exchange time, i.e. the time required to replace the finished reel or roll with a new winding mandrel, is reduced.  
       [0012] This and other objects and advantages, which will be clear those skilled in the art in the text that follows, are essentially obtained by a rewinding machine of the above mentioned type, comprising a pair of lateral flanks, on each of which a corresponding guide defining a closed path is arranged, along which a plurality of said mating centersa are mobily arranged. The mating centers are arranged on the two flanks so that each mating center carried by one of said flanks corresponds to and is axially aligned with a mating center carried by the other of said flanks. A system is also provided to drive the mating centers along each of the guides.  
       [0013] In this arrangement, a first pair of mating centers engages a reel or roll under formation and a second pair of mating centers engages a new mandrel simultaneously. The finished reel can be conveyed from the winding cradle to the unloading area and simultaneously the new mandrel can be conveyed from a loading area to the winding cradle by moving the pairs of mating centers along the closed path. This leads to a considerable increase in the total rewinding cycle speed due to the reduction of the time required to exchange the reel or roll with a finished mandrel.  
       [0014] In addition to increasing the production cycle speed, the rewinding machine according to the invention provides a number of additional advantages. Such advantages include improved control of the reel during the unloading phase and more accurate control of the web cutting phase for forming the trailing end of the finished reel and the leading end of the web to be used for winding a new reel to be formed on the new mandrel.  
       [0015] Currently, the finished reel or roll is ejected from the winding cradle, typically defined by a pair of winding cylinders, by pushing and rolling. The reel is then positioned in an unloading device in a position which is not exactly repeatable at each cycle with consequently possible difficulties in the web cutting phase for starting the winding of the following reel.  
       [0016] In a practical embodiment of the invention, each mating center can be carried by a respective carriage which slides on the guide of the corresponding flank.  
       [0017] Furthermore, advantageously, it can be foreseen that the path defined by said guides extends from a first mandrel engagement position to a second finished reel unloading position; said winding cradle being arranged between said first and said second position.  
       [0018] In a practical and advantageous embodiment, the handling system comprises a continuous flexible member onto which the mating centers associated to the respective flanks are secured on each flank. Moreover, a drive is provided for moving said flexible member. Each motor can drive two flexible members. In this case, the movements of the mating centers on the two flanks will be synchronized by means of an appropriate mechanical transmission. Alternatively, two separate motors can be used and synchronized electronically by means of a control unit, i.e. using an electric axis. This solution presents the advantage of avoiding the presence of cumbersome mechanical members between the two flanks.  
       [0019] Other arrangements of the members moving the mating centers along the path defined by the guides on the two flanks can be envisaged. For example, in principle, the mating centers can each be equipped with an actuator which controls the movement along the guide with a suitable control for synchronizing the movement of each mating center.  
       [0020] In an advantageous embodiment of the machine according to the invention, a taker-in is provided to insert the winding mandrels moving from a collection position of the winding mandrels to a release position of the winding mandrels, in correspondence with the position in which the mandrels are engaged by the mating centers. The taker-in may consist of a pivoting member but might also be made in a different way. For example, the winding mandrels could be inserted axially, i.e. with a movement parallel to their axis inside a fixed support, such as a cradle or other. The mandrels can be collected from this location by the mating centers as they move along said closed path. Alternatively, the taker-in can be equipped with an insertion movement which is not pivoting, e.g. by translating from a mandrel collection position to a mandrel release position.  
       [0021] The winding cylinders can be made so that during the winding phase the axis of the reel or roll (and consequently of the winding mandrel) is always in the same position. This can be obtained in a Sway which is known per se employing mobile axis winding cylinders with a vertical movement component so that the winding cradle is gradually lowered according to the increased diameter of the reel. In this case, the two flanks can be fixed and the mating centers can be held constantly at the same height for the entire reel winding phase. Conversely, if the winding cylinder axis is fixed or if the winding cylinders move in such a way that the axis of the reel being formed is provided with a gradual vertical or slanted raising movement, the flanks will also be vertically mobile and actuator means will be provided to control the upwards and downwards movement of said flanks according to the diameter of the reel. Synchronization means will be advantageously provided for the vertical movement of the flanks also in this case.  
       [0022] In general, the two winding cylinders can be mobile one with respect to the other and can be opened, e.g. one can have a fixed axis and the other a mobile axis according to a horizontal trajectory. This increases the suporting base of the reel as it gradually increases in diameter during the winding operation. In this case, the axis of the reel will follow a more or less complex trajectory with a movement which has a vertical component and a horizontal component. The trajectory followed by the axis of the reel changes according to the characteristics of the product (specifically its thickness) and the working conditions of the machine. The movement can be made by the mating centers by forming a complexly shaped guide according to the trajectory of the reel axis or preferably by combining a gradual raising movement of the flanks to a translating movement of the mating centers along a portion of the closed path which can simply be a straight horizontal portion.  
       [0023] In principle, the rewinding machine can have only two lower winding cylinders arranged side-by-side, either mobile or fixed as illustrated above, to. withhold the reel under formation. Preferably, in a way which is known per se, the rewinding machine comprises a third cylinder whose axis is parallel to the first and the second winding cylinder arranged over the winding cradle and mobile to allow for the increased diameter of the reel developing between said first, second and third cylinder. This arrangement improves reel guidance. Advantageously, the third cylinder is carried by a pair of pivoting arms whose fulcrum is in a position which does not interfere with the flanks (which may be mobile) carrying the guides which define the closed path followed by the mating centers. The third cylinder can be idle or preferably driven with a peripheral speed which is essentially equal to the peripheral speed of the first and the second winding cylinder, it being understood (in a way that is known per se) that the three cylinders can have slightly different peripheral speeds to obtain the required degree of compactness in winding the reels.  
       [0024] A variable number of mating centers can be provided along each of two guides carried by said flanks also according to the type of movement adopted. The number of mating centers on each side will appropriately be equal to at least three and preferably equal to five.  
       [0025] When the machine is provided with a taker-in for inserting the winding mandrels, it can advantageously present a winding mandrel resting cradle whose geometry corresponds to that of the winding cradle in the initial winding phase. As clearly described in the example of embodiment that follows, this arrangement ensures correct handling without the need for adjustments in the presence of mandrels with variable diameters.  
       [0026] According to a possible form of embodiment of the rewinding machine according to the invention, electric or pneumatic distribution means are associated to each flank, since the mating centers approach and distance the mandrel and may be provided with control sensors. Furthermore, the mating centers can either be idle or driven. A motor is associated to each of said mating centers in the second case, e.g. an electric motor, to turn them. The motor is powered by said electric distribution means.  
       [0027] The distribution means can comprise a rotating distributor for each flank arranged inside the path defined by the guide along which the mating centers move and one or more flexible members towards said mating centers. Preferably, however, an electrical distribution box and a pneumatic distribution box can slide along each of said guides; said electrical distribution box and said pneumatic distribution box can be connected by means of flexible members to a distributor arranged inside the path defined by the guides along which the mating centers and said boxes move; and said boxes can be connected to the mating centers via flexible pneumatic and electric connections.  
       [0028] The invention also relates to a method for the production of reels of web wound on winding mandrels in which:  
       [0029] a first winding mandrel is inserted in a winding cradle and a predetermined amount of web is wound upon it to form a reel, the ends of said first mandrel being engaged by a pair of mating centers;  
       [0030] the finished reel is unloaded from the winding cradle and  
       [0031] a second winding mandrel is inserted in said winding cradle.  
       [0032] Characteristically, the method according to the invention comprises the following phases:  
       [0033] engaging the first winding mandrel in a collection area by means of a first pair of mating centers;  
       [0034] transferring the first winding mandrel by means of said mating centers to said winding cradle;  
       [0035] when the reel has been completed, transferring the finished reel with said first pair of mating centers from said winding cradle to an unloading area;  
       [0036] after transferring said first winding mandrel to the winding cradle (e.g. while winding said reel), engaging a second winding mandrel with a second pair of mating centers in said collection area;  
       [0037] when said reel is removed from the winding cradle, inserting the second winding mandrel in said winding cradle with said second pair of mating centers;  
       [0038] transferring the first pair of mating centers towards the collection area of the winding mandrels.  
       [0039] Additional advantageous characteristics and embodiments of the machine according to the invention are set forth in the annexed claims. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0040] The invention will be better understood following the description and the enclosed drawing, which shows a non-limitative practical embodiment of the invention. In the drawing, in which identical parts have the same reference numerals, it is shown the following:  
     [0041]FIG. 1 is a schematic cross-sectional view according to I-I in FIG. 1 of a machine according to the invention;  
     [0042]FIG. 2 is a view according to II-II in FIG. 1;.  
     [0043]FIG. 3 is a cross-sectional view according to III-III in FIG. 1;  
     [0044]FIG. 4 is a cross-sectional view IV-IV in FIG. 1;  
     [0045]FIG. 5 is a front view from inside the machine of one of the flanks with the pneumatic and electric distribution means;  
     [0046]FIG. 6 is a partial cross-sectional view according to VI-VI in FIG. 5; and  
     [0047] FIGS.  7 A- 7 F show the winding cycle in sequence. 
    
    
     DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION  
     [0048] Above and in the following description, reference is made to the formation of a reel on the winding mandrel. In actual fact, the reel under formation can be formed by a plurality of single reels arranged side-by-side which simultaneously receive the same length of web by winding strips of web obtained by longitudinally cutting the single incoming web, since the winding cycle can be carried out on tubular cores axially aligned on the mandrel. Consequently, in the present description and in the attached claims the term “reel” can herein indicate a single reel or a plurality of axially aligned reels formed at the same time in general.  
     [0049] The rewinding machine comprises a fixed structure  1  with two lateral flanks fastened to the base. The fixed structure  1  carries a pair of winding cylinders  3 ,  5  whose axes are parallel defining a winding cradle  7  in which the winding mandrels are arranged with one or more cores made of cardboard, plastic or other suitable material fitted upon them. The cores are fitted and secured on the mandrels by expansion of the mandrels in a way which is known per se in a station outside the rewinding machine.  
     [0050] Cylinders  3 ,  5  are motor driven (in a way which is known per se) to turn the winding reel. The web N is turned around winding cylinder  3  which is supplied along a feeding path defined by rollers  9 ,  10 ,  11 ,  12 ,  13 ,  14  from a parent reel (not shown). Blades (not shown) are arranged along the feeding path. The blade cuts the web N in the longitudinal direction into strips corresponding (in terms of dimension and position) to the longitudinal dimension and the position of the tubular winding cores inserted on the winding mandrels which are inserted in the winding cradle  7  as described below.  
     [0051] The structure  1  also supports a pair of arms  17  pivoting at  19  on the structure  1 . The pair of arms supports a third winding cylinder  21 . The latter can either be idle or driven and rests on the top of the reel under formation, such that in the winding cradle the reel rests on the lower winding cylinders  3 ,  5  and is controlled and withheld by the third winding cylinder  21 . Reference numeral  23  indicates the cylinder-piston actuators which control the pivoting movement of the arms  17  on the fulcrum  19  for gradually raising the upper mobile winding cylinder  21  while the reel under-formation grows in diameter and for lowering it towards the cradle  7  at the beginning of a new winding cycle after unloading the finished reel and inserting a new mandrel in the winding cradle  7 .  
     [0052] In the example shown, the winding cylinder  3  has a fixed axis and the supports are integral with the structure  1  while the axis of the winding cylinder  5  is mobile in the horizontal direction for the purposes explained below. For this purpose, the supports are mounted on carriages  25  which slide on horizontal guides  27  integral with the two flanks of the fixed structure  1 . A threaded bar  29  and an actuator  31  control the movement of the carriages  25  along the guides  27  to approach and distance the winding cylinder  5  with respect to the winding cylinder  3 .  
     [0053] A mobile carriage  33  is arranged on the opposite side of the rewinding machine with respect to the web N feeding path. The carriage  33  moves along rails  35  integral with the base and equipped with a pair of resting rollers  37  for distancing the finished reels or rolls from the rewinding machine. Reference f 33  indicates the approaching and distancing movement of the carriage  33  with respect to the winding area defined by the winding cylinders  3 ,  5 . The carriage is also equipped with a rolling plane  39  on which the reels to be distanced are received.  
     [0054] Vertical guides  41  on which the respective flanks  43  slide are integral with each of the two sides of the structure  1  on the side facing the inside of the machine. The two flanks  43  are reciprocally parallel and vertically mobile along the guides  41 . Consequently, the two flanks can move on planes which are parallel to the median plane of the rewinding machine according to the double arrow f 43 . The upwards and downwards movement of the flanks  43  is controlled by a pair of cylinder-piston actuators  45  in which the cylinder is fastened to the structure  1 . A synchronization system comprising a transversal shaft  47  supported by the flanks of the fixed structure  1  to synchronize the movements of the two flanks avoiding the possibility of non identical movements in the vertical direction. Two toothed pulleys  49  are fitted near the two ends of the transversal shaft  47  which project outside the flanks of the structure  1 . Respective toothed belts  51  turn on the pulleys, each of which additionally turns on a respective second toothed pulley  53  carried by the respective flank. Each toothed belt  51  is fastened in point  55  to the corresponding flank. In this way, the two flanks  43  are forced to move identically along the vertical guides  41 .  
     [0055] A linear guide  61  defining a closed path is provided on each said flank  43 . In the example show, the path consists of two reciprocally parallel straight sections whose ends are joined by two semicircular sections of the path.  
     [0056] A plurality of carriages  63  slides along each linear guide  61 . Five carriages for each linear guide  61  and consequently for each flank  43  are provided in the example shown. The carriages  63  are reciprocally arranged at an equal distance along the path defined by the guide  61 . Each carries a mating center  65  intended to engage one end of the winding mandrels. The mating centers  65  can have any possible configuration and, in general, move axially to approach and distance the winding mandrels and present expandable heads  67  to be fastened onto the mandrels. Other types of gripping members can be used instead of expandable heads. Alternatively, single mating centers can be used, which are inserted in the mandrels without additional tightening effect. This solution is particularly suitable if the mating centers are not motor driven.  
     [0057] According to the arrangement of the carriages  63  and the respective mating centers  65  on the two flanks  43 , a mating center on one side corresponds to a mating center on the opposite side, the mating centers being axially aligned to engage a respective winding mandrel held parallel to the axes of the winding cylinders  3 ,  5 ,  21 .  
     [0058] The carriages  63  associated to each side  43  are fastened to a toothed belt  68  (or other equivalent flexible member) turning on two toothed pulleys  71 ,  73 . The toothed pulley  71  on each flank  43  is driven by a stepper motor  75  or other suitable actuator for accurately controlling the movement of the pulley  71  and consequently of the various carriages  63  which are fastened to the corresponding toothed belt  68  by means of a controlling program. The two motors  75  associated to the two flanks  43  are joined together by an electrical axis, i.e. are controlled by a central unit so that the two pulleys  71  and the two toothed belts  68  are moved in a perfectly synchronized way. In the example shown, the motors  75  are on the opposite side of the flanks  43  with respect to the side on which the guides  61 , the carriages  63  with the mating centers  65  and the pulleys  71 ,  73  with the toothed belt  68  are arranged.  
     [0059] A taker-in  83  is arranged on the inlet side of the web N of the fixed structure  1  and pivots in point  81  for inserting the winding mandrels with the respective tubular cores fitted and fastened to them. The taker-in  83  pivots on the axis  81 . The pivoting movement is controlled by a cylinder-piston actuator  85  or by a pair of actuators symmetrically arranged on the two flanks of the machine. The structure  1  carries in addition a V-section fixed duct  87  in which the winding mandrels and tubular cores fitted and fastened on them are axially inserted. The duct  87  presents a comb structure so that the taker-in  83 , also presenting a comb structure, can penetrate inside it.  
     [0060] In its lower position, the taker-in  83  is partially arranged under the resting surface of the duct  87  so that a mandrel with the respective tubular cores can be inserted axially along the duct. Once the mandrel is positioned in the duct  87 , the taker-in can pivot upwards thus picking up the mandrel and bringing it in a position in which it can be engaged by the mating centers  65  which move along the flanks  43  and carried towards the winding cradle.  
     [0061] Alternatively, the duct  87  can be omitted. In this case, the taker-in  83  can be made of continuous profiles inside of being comb-like. The mandrel can thus be axially inserted in the cradle defined by the taker-in  83  when this is in the lower position, shown with a dotted line in FIG. 1. An appropriate shape will be adopted for the taker-in to prevent the mandrel from dropping from the taker-in.  
     [0062] As shown in the drawing, the taker-in  83  presents a profile defined by two circular cylindrical surface sections corresponding to the profile of the winding cradle formed by the two cylinders  3 ,  5  when they are in the maximum approach position. This allows the use of mandrels with various diameters without needing adjustments, as clearly appears in the following description of machine operation.  
     [0063] The operation of the rewinding machine described above will now be illustrated with reference to the sequence in FIGS.  7 A- 7 F. In FIG. 7A, the five carriages carried by the flank  43  and shown therein are indicated by reference numerals  63 A,  63 B,  63 C,  63 D,  63 E. Carriage  63 A with the respective mating center is arranged in correspondence with the cradle  7  defined by the winding cylinders  3 ,  5  which are in the maximum approach position. The mating center  65  of the carriage  63 A and the mating center, which is axially aligned therewith of the corresponding carriage carried by the other flank engage a winding mandrel M with the respective tubular cores fitted on it. The mating centers of the carriages in position  63 E have unloaded the previously formed roll, which was already removed. The mating centers carried by the carriages in position  63 B are aligned in correspondence with the top position of the taker-in  83  which contains the winding mandrel M 1  which will be inserted in the winding cradle during the following cycle. The taker-in  83  could actually be still in the lowered position and take the mandrel M 1  from the duct  87  at a later instant. The reel or roll made during the previous cycle could also still be inside the machine supported by the mating centers carried by the carriages  63 E or may have been unloaded onto the carriage  33  and the latter may still be near the pair of winding cylinders  3 ,  5 .  
     [0064] The winding cycle starts in the conditions illustrated in FIG. 7A. The web N is wound on the winding mandrel M on the tubular cores, which are fitted and fastened on the mandrel. The mating centers which engage the mandrel M in the winding cradle could be motor driven to turn with the mandrel but this is not necessary. The torque for turning the mandrel and consequently winding the web is provided by winding cylinders  3  and  5  (which are motor driven). The upper winding cylinder  21  is lowered and taken into contact with the winding mandrel in the cradle between the winding cylinders  3  and  5  when a suitable number of turns of web have been formed on the mandrel.  
     [0065] Progressively, as the web N is wound around the winding mandrel M, the machine goes from the arrangement shown in FIG. 7A to the arrangement shown in FIG. 7B which differs from the previous arrangement for the upwards movement of the upper winding cylinder  21  and the corresponding upwards movement of the flanks  43  due to the upwards movement of the axis of the reel under formation. This figure shows how the new winding mandrel M 1  being lifted by the taker-in  83  is engaged by the mating centers carried by the carriages  63 B and the taker-in is lowered again to take a new mandrel.  
     [0066] In FIG. 7C, the diameter of the reel R has increased again. In order to provide a large resting base for the reel R, the winding cylinder  5  was distanced from the winding cylinder  3  with a horizontal movement, causing the winding cradle  7  to widen in size. This causes the need to translate the mating centers of the carriages  63 A horizontally in addition to vertically to follow the increasing diameter of the reel R. This causes a corresponding movement along the linear guide  61  of the other two carriages (all reciprocally bound to the toothed belt  68 ) but does not cause problems because the following winding mandrel M 1  has already been engaged by the mating centers in position  63 B while the previous reel has been unloaded by the mating centers carried by the carriages  63 E. A new winding mandrel M 2  will have been introduced in the duct  65  in the meantime for the next winding cycle.  
     [0067] In FIG. 7D, the winding cylinder  5  appears additionally distanced from the winding cylinder  3  and the reel R has increased in diameter again reaching its final dimension. The upper winding cylinder  21  is additionally raised. The flanks  43  are raised to follow the upwards movement of the axis of the reel R and consequently of the winding mandrel M while the carriages carrying the mating centers are translated to follow the movement in the horizontal direction of the axis of the reel following the opening of the winding cylinders  3 ,  5 .  
     [0068] In FIG. 7E, the finished reel R has been transferred from the winding cradle to the carriage  33 . For this purpose, the flanks  43  have been slightly risen to permit the translation of the reel R by moving the carriages  63 A towards the carriage  33 . The plane  39  of the carriage  33  is taken to a position which is approximately tangent to the winding cylinder  3  and the mating centers of the carriages  63 A are taken over the resting rollers  37  of the carriage  33 . The translation of the carriages  63 A causes the translation of all the other carriages  63  so that, for example, the carriages  63 B are moved above the winding cradle  7  which in the meantime has newly decreased in size because the winding cylinder  5  has approached again the winding cylinder  3 . The upper winding cylinder  21  was raised to allow the passage of the finished reel.  
     [0069] In FIG. 7F, the carriage  33  was distanced from the winding cylinders ;after that the reel R was deposited by the mating centers carried by the carriages  63 A which were reciprocally distanced for this purpose. Cutting means (not shown, and known per se) are used to transversally cut the web N between the winding cradle  7  and the finished reel R. The leading edge of the web which is thus formed is anchored to the tubular cores fitted on the mandrel M 1  which is then introduced in the winding cradle  7 . The flanks  43  are lowered to take the mandrel M 1  engaged by the mating centers of the, carriages  63 B in the winding cradle in contact with the winding cylinders  3 ,  5 . This downwards movement also takes the mating centers of the carriages  63 C into correspondence with the taker-in  83  which in the meantime was raised to take and lift the winding mandrel M 2  from the duct  87  to the position where it is engaged by the mating centers of the carriages  63 C.  
     [0070]FIG. 7F—as FIG. 7A—shows an instant of the winding cycle in which the mating centers engaging the mandrel which is in the winding cradle  7  and the mating centers engaging the mandrel intended for the following cycle are in a position which depends on the diametrical dimension of the winding mandrels, or more precisely on the diametrical dimension of the tubular cores fitted and fastened onto them. Thanks to the particular configuration of the taker-in  83 , which presents a profile that copies that of the winding cradle in this configuration, it is sufficient to adjust the position of the mating centers with respect to the winding cylinders  3 ,  5  to automatically obtain the correct position of the mating centers with respect to the seat defined by the sections which form the taker-in  83  as the diameter of the tubular cores varies.  
     [0071] From the description above, it is clear that the unloading phase of finished reel R and the introduction of a new winding mandrel in the cradle  7  is much faster than what occurs in rewinding machines of the traditional type. This reduces the overall duration of a winding cycle. Furthermore, the finished reel R is controlled and guided until it reaches the rollers  37  of the carriage  33  and this facilitates the unloading operations of the reel and the cutting of the web because the position which the reel R assumes on the carriage  33  is always accurately repeatable.  
     [0072] It is clear form what has been described above, that the mating centers  65  and the respective heads  67  are mobile. Particularly, the mating centers are provided with approaching and distancing movement with respect to the winding mandrels for gripping and releasing and with a fastening movement, e.g. expansion of the heads  67 , to fasten the winding mandrel which is used at the time by a pair of mating centers. As mentioned, the mating centers may be motor driven. This means that electrical signals must be provided to the mating centers for the control units which operate the mechanical members (e.g. solenoid valves or other). The possibility of sending or receiving electrical signals to and from the mating centers obtained via sensors, e.g. enabling signals for carrying out the various functions of the cycle in sequence. Finally, the mechanical members must be operated via pneumatic or hydraulic controls, reasons for which compressed air or other pressurized fluid must be supplied to the mating centers.  
     [0073] For this purpose, in the illustrated embodiment, a rotary compressed air and electrical signal distributor is required to operate the mechanical members arranged inside the closed path defined by the linear guide  61  of each flank  43  in a position which is slightly central with respect to said path. The rotating distributor and the connection means to the electric and pneumatic line to the various mating centers are indicated only in FIGS. 3, 5 and  6 , while they are substantially omitted in the remaining figures of the drawing for the sake of clarity.  
     [0074] The rotating distributor is generally indicated with reference numeral  91 . The rotating distributor is connected by means of at least an electric wire to an electric unit  93  fitted on a carriage  94  sliding on the same guide  61  on which the carriages  63 , carrying the mating centers  65 , slide. The carriage  94  can also be fastened to the corresponding toothed belt  68 . Reference numeral  95  indicates a flexible channel in which the electric wire is arranged, one end of the channel being connected to the rotating distributor  91  and the opposite end to the electric unit carriage  94 . The electric wire is not shown in the drawing for the sake of simplicity.  
     [0075] The electric unit  93  is connected in series to the carriages  63  and from here to the various mating centers carried by the carriages by means of electric wires arranged in flexible channels  97 . Each channel  97  joins a carriage  63  to an adjacent carriage. In this way, the electrical signals supplied via the rotating distributor  91  reach all the mating centers on the respective flank  43 .  
     [0076] A compressed flexible air conduit also passes in the channel  95 . The compressed air line is also passed to a pneumatic unit  101  and to all the carriages  63  and finally to the respective mating centers  65  via channels  99  which are parallel to channels  97 . In this way, the compressed air reaches all the mating centers and the respective actuators which are controlled by the compressed air with control signals distributed along the electrical line which from the rotating distributor  91  reaches the electric unit  93  and from here all the carriages  63 .  
     [0077] In the example described above, the winding cylinders  3 ,  5  are reciprocally mobile to increase the resting base during the winding cycle as the diameter of the reel R under formation increases. This characteristic is advantageous specifically for reels R whose final diameter is particularly high. The machine can be programmed so that the winding rollers only open and close if the diameter of the reel exceeds a certain value. The opening movement can be controlled, for example, according to the amount of wound web determined by means of an encoder associated to one of the cylinders or rollers arranged along the material path or also to one of the two winding cylinders. Alternatively, the diameter can be controlled and the cylinders can be opened according to the respective signal.  
     [0078] Since the opening of the winding cylinders is required to make the winding operation more stabile either eliminating or limiting reel vibrations, according to a possible form of embodiment, opening movement control of the two cylinders can be consequent to a signal from load cells associated to the mating center supports  65 . When these load cells or other equivalent sensors detect a vibration exceeding a predetermined threshold value, the rewinding machine control unit controls the gradual opening of the cylinders  3 ,  5  until the detected vibration is again reduced to an acceptable value.  
     [0079] It is noted that the drawing shows just one embodiment of the invention, which may vary in shapes and arrangements, without departing from the scope of the present invention. The presence of reference numerals in the annexed claims has the purpose of facilitating comprehension of the claims with reference to the preceding description and the annexed drawings and does not limit its scope of protection.