The present invention refers to a device and to a method for separating and transporting groups of flat items, such as borders or paper sheets deposited by a folding machine. More in particular, the present invention regards separating and transporting borders or paper sheets during their deposition or formation, with the aim of mechanically obtaining packages formed by a predetermined number of paper napkins or the like.

Production of paper napkins is currently carried out by means of folding machines essentially comprising two contra-rotating rolls, thrust means and a knife. The paper ribbon coming from the reel towards the rolls is seized by a gripper present on one of the rolls and dragged between the rolls and beyond, up to a given position in which the gripper releases it, leaving the border folded. Analogously, a gripper present on the other roll in turn carries out a similar operation, generating an identical border on the other side of the conveyor belt downstream of the pair of rolls.

The abovementioned operations are repeated so as to position the paper borders one after the other, to the right and to the left, downstream of the contact area of the rolls, providing a zig-zag folded paper ribbon. Thrust means, constituted by curved rods or the like, are housed in special lowered seats obtained on the lateral surface of the rolls and are driven outside the seats after the formation of each border. The thrust means move away the borders of the folded ribbon, to create space for the new incoming border each time, and move such borders against a knife which cuts the folded ribbon in half, dividing it into two adjacent stacks of napkins .

In order to accurately determine the amount of napkins to be inserted into each package, downstream of the folding machine a separation and transport device is provided, comprising one or more supports, each carrying at least one finger element for separating the sheets. The finger elements and the relative supports are mounted on slidable guides, one for each outer side of the two adjacent stacks of napkins, which move along a closed path parallel to the stacks. The finger elements and the relative supports are also controlled between a waiting position, in which they remain immobile upstream of the area for forming the borders, and an operative position, in which they move along the respective guides, being selectively inserted between groups of napkins . The amount of napkins present in each group is determined by special control means capable of taking each finger element from the waiting position to the operative one whenever the predefined number of napkins is obtained.

Each of the two slidable guides of the separation and transport device is usually made in form a driven conveyor belt, on which the finger elements and the relative supports are constrained through magnets which operate on the metallic body of the supports. See, for example, European patent N. EP 0 294 675 Bl on behalf of the present applicant. In order to obtain an effective operation of the separation and transport device, the translation speed of the finger elements should be linked to the speed of the napkins production line or, even better, slightly lower than the output speed of the napkins for about the first three quarters of the length of the slidable guides. On the last portion of the napkins production line, the speed of the slidable guides should be higher, so as to facilitate the division of the groups of napkins. The speed of slidable guides of current devices for separating and transporting napkins is instead constant over the entire portion of the napkins production line.

Thus, an object of the present invention is that of providing a device and a method for separating and transporting groups of flat items, in particular paper napkins, capable of overcoming the aforementioned drawbacks of the prior art in an extremely simple, inexpensive and particularly functional manner.

In detail, the object of the present invention is that of providing a device and a method for separating and transporting groups of flat items which allow efficiently varying the speed of the separation elements according to the speed of transport of the flat items being handled.

Another object of the invention is that of providing a device for separating and transporting groups of flat items that does not interfere with the operation of other machinery for handling said objects themselves, i.e. not causing slowing down and jamming thereof .

The objects according to the present invention are attained by providing a device and a method for separating and transporting groups of flat items, in particular paper napkins, as outlined in the independent claims.

Further characteristics of the invention are outlined by the dependent claims, which are an integral part of the present description.

Characteristics and advantages of a device and a method for separating and transporting groups of flat items, in particular paper napkins, according to the present invention will be more apparent from the following exemplifying and non-limiting description with reference to the attached schematic drawings wherein:

figure 1 is a top schematic view of a folding machine provided with a pair of devices for separating and transporting groups of flat items according to the present invention;

figure 2 is a perspective view of the machine and devices of figure 1; figure 3 is a top, partial and enlarged view of a finger separator element of the device for separating and transporting groups of flat items according to the invention;

figure 4 is a perspective, partial and enlarged view of the device for separating and transporting groups of flat items according to the invention;

figure 5 is another perspective, partial and enlarged view of the device of figure 4 ;

figures 6 and 7 are partial views respectively showing the tailing and leading ends of the device of figure 4;

figure 8 is a side elevational view of the device of figure 4; and

figure 9 is a cross-sectional view, obtained along the line A-A of figure 8, of the device of figure 4.

With reference to the drawings, a device for separating and transporting groups of flat items according to the present invention, indicated in its entirety with reference number 10 and applicable to a folding machine of the type provided with contra- rotating rolls 12 and 14 is shown. The folding machine is fed with a paper ribbon 16 which, in the example case of the formation of napkins, was previously folded into two in the longitudinal direction.

The paper ribbon 16 is seized by a gripper (not shown) present on one of the two contra-rotating rolls, for example the roll 12, and it is dragged on the surface of such roll 12 up to a given position A (figure 3) in which the gripper releases it, thus forming a first folded border. In the meanwhile, a second gripper present on the other roll, i.e. the roll 14, carries out the same operations as described above, releasing the paper ribbon 16 at a position corresponding and symmetrical to that indicated with A in figure 3, forming a second folded border opposite to the first border.

Two opposite borders 18, one for each roll, which are inserted immediately upstream of the previously formed borders are thus formed on the paper ribbon 16 upon each rotation of the contra-rotating rolls 12 and 1 . In order to clear the required space for the incoming borders, the previously formed borders 18 are pushed downstream of the two contra-rotating rolls 12 and 14 through pressure means 20 consisting of non- rotating arched bars, housed in lowered circumferential seats 22 provided on the surface of the contra-rotating rolls 12 and 14. In particular, after depositing each border, the arched bars 20 perform an alternating movement, exiting from the respective seats 22 to push the borders 18 of the ribbon 16 forward and against a knife 24 located downstream of the contra-rotating rolls 12 and 14. The knife 24 thus cuts the folded ribbon 16, transforming the borders 18 into a double stack of napkins 26.

Preferably the napkins 26 lie on a feeding support 28 on which they are moved away from the contra- rotating rolls 12 and 14 at a predefined speed depending on the formation production rhythm. Thus, a separation and transport device 10 capable of defining a stack of napkins 26 formed by a predetermined number of such napkins 26 is provided on each of the two opposite sides of the feeding support 28. Each separation and transport device 10 is actually provided with a plurality of finger or tab elements 30 which are inserted, at predefined intervals, between the groups of napkins 26. Pairs of finger elements 30 move upstream and downstream of each of such groups, at the same speed with respect thereto, over a predefined portion of path, at the end of which a gripper or an analogous element picks up the assembly comprising the predefined number of napkins 26, defined by the distance between the two finger elements 30 of the abovementioned pair, for packaging thereof.

In detail, each finger element 30 of the device 10 is mounted on a support 32 movable along a closed path 34. In turn, the closed path 34 comprises a first going portion 36, disposed side- to-side and parallel to the feeding support 28, along which the finger elements 30 can engage with the napkins 26, and a second return portion 38, along which the finger elements 30, after accompanying the groups of napkins 26 towards the packaging machine, are returned to the proximity of the two contra-rotating rolls 12 and 14 in order to engage with new groups of incoming napkins 26.

The finger elements 30 and the relative supports 32 are moved along the going 36 and return 38 portions of the closed path 34 through powered movement means. Each support 32 of the finger elements 30 can be connected to the powered movement means through engaging and disengaging elements 40, preferably of the magnetic type, present inside the powered movement means. The engaging and disengaging elements 40 allow engaging and disengaging the connection between movement and support means 32 to determine the stop or forward movement of the latter according to need.

According to the invention, the powered movement means present at least along the going portion 36 of the closed path 34 of each device 10 consist of two side-to-side conveyor belts 42 and 44 of the same length, operated at different speeds one from the other and each provided with engaging and disengaging elements 40 which are selectively activable to drag the finger elements 30 and the relative supports 32 on one or the other conveyor belt according to the feeding position of the groups of napkins 26. In detail, according to a preferred aspect of the present invention, the first conveyor belt 42 of the going portion 36, located in the close proximity to the feeding support 28 of the napkins 26, is operated at a lower speed with respect to that of the second conveyor belt 44 parallel thereto. Such lower speed of the first conveyor belt 42 is substantially equal with the speed of the groups of napkins 26 on the feeding support 28, or it is slightly lower with respect thereto. Hence, the second conveyor belt 44 of the going portion 36, located more externally with reference to the feeding support 28 of the napkins 26, is operated at a higher speed with respect to that of the first conveyor belt 42.

According to a particularly preferred aspect of the invention, the percentage difference between the speed of the first conveyor belt 42 (slower) and the speed of the second conveyor belt 44 (faster) of the going portion 36 is in a range from about 15% to about 20% (preferably about 17%) .

Regarding engaging and disengaging elements 40, they are preferably activated inside the first conveyor belt 42 of the going portion 36 in a range from about the first 2/3 (66%) to the first 3/4 (75%) of the length of the first conveyor belt 42. Hence, the engaging and disengaging elements 40 present inside the second conveyor belt 44 of the going portion 36 are preferably activated solely in a range from about the last one third (33%) to the last quarter (25%) of the length of the second conveyor belt 44.

The two side-to-side conveyor belts 42 and 44 of the going portion 36 are preferably operated by a single gear-motor assembly 46, provided with two or more driving shafts 48 and 50 having different transmission ratios in order to activate the two conveyor belts 42 and 44 independently and at different speeds. The gear-motor assembly 46 can be arranged to activate, through a special transmission shaft, a further conveyor belt 52 which constitutes the movement means present along the return portion 38 of the closed path 34. Such conveyor belt 52 of the return portion 38 can be operated at a different speed with respect to the speed of the two conveyor belts 42 and 44 of the going portion 36, the speed rate of the conveyor belt 52 however requiring optimisation to obtain a good operation of the device 10.

During the operation of the device 10, a first support 32 with relative finger element 30 is taken to the waiting or starting position upstream of the going portion 36 of the closed path 34, in proximity of each roll 12 or 14, where it is retained by a stop element 54. In this condition, the operating terminal end of the finger element 30 is maintained in a manner such not to interfere with the formation or deposition of the borders 18 of the paper ribbon 16.

After folding a predefined number of borders 18, which can be preselected at will, the stop element 54 is automatically disengaged, releasing the support 32 that immediately engages with the first conveyor belt 42 of the going portion 36 of the closed path 34, due to the activation of the relative magnetic engagement and disengagement elements 40. Simultaneously, the finger element 30 immediately engages the border 18 in front of it, pushing it forward at the speed of the first conveyor belt 42 and clearing the space for the subsequent incoming border. Along this first portion of the going portion 36 of the closed path 34, defined by the engagement between the support 32 and the first conveyor belt 42, the finger element 30 substantially moves at the same speed rate of the borders 18, that are then cut by the knife 24 to form the double stack of napkins 26, each stack of napkins 26 being defined by two subsequent finger elements 30 that separate said stack from the previous and subsequent napkins.

At a given predefined point of the path of the stack of napkins 26 on the relative feeding support 28, each support 32 with the relative finger element 30 disengages from the first conveyor belt 42 of the going portion 36 and, simultaneously, it is connected to the second conveyor belt 44 by the relative engaging and disengaging elements 40. Thus, the support 32 and the relative finger element 30 can move faster to move the stack of napkins 26 away from the area for forming the borders 18 and thus facilitate the subsequent step of picking up such stack of napkins 26. In fact, when each support 32 with the relative finger element 30 has been released by the napkins 26, the stack containing the predefined number of napkins 26 is picked up by a gripping element to execute the subsequent packaging step . Upon reaching the end of the going portion 36 of the closed path 34, where they are transported by the second conveyor belt 44, the supports 32 with the relative finger elements 30 are moved on the return portion 38 of the closed path 34, for example through a pneumatic translator element 56 or the like. The conveyor belt 52 of the return portion 38 shall thus return the supports 32 and the relative finger elements 30 towards the abovementioned waiting or starting position, where they are stopped awaiting to restart the previously described operating cycle. Such stop preferably occurs through disengagement from the conveyor belt 52, with the supports 32 lying against an end stop element waiting for another pneumatic translator element 58 or the like to take them to the waiting or starting position.

It has thus been observed that the device and the method for separating and transporting groups of flat items, in particular paper napkins, according to the present invention attain the previously described objects. In particular, the possibility of varying the speed of the separator elements in the step of preparing the package of napkins allows optimizing the preparation of the package, without slowing or jamming the entire napkin production cycle.

The device for separating and transporting groups of flat items of the present invention thus conceived can be subjected to numerous modifications and variants, all falling within the same inventive concept; furthermore, all details can be replaced by technically equivalent elements. Practically, the materials used, as well as the shapes and dimensions, may vary according to the technical requirements.

Thus, the field of protection of the invention is defined by the attached claims.