WO2011151791A1

WO2011151791A1 - Unit and method for feeding folded tissue products or the like in a revolving drum packaging machine

Info

Publication number: WO2011151791A1
Application number: PCT/IB2011/052400
Authority: WO
Inventors: Renzo Tommasi
Original assignee: Rent S.R.L.
Priority date: 2010-05-31
Filing date: 2011-05-31
Publication date: 2011-12-08
Also published as: CN103025612B; CA2801044A1; RU2012157976A; US20130219837A1; ITFI20100121A1; RS53640B1; EP2576352B1; CN103025612A; IT1400205B1; EP2576352A1; RU2568748C2

Abstract

An apparatus for packaging stacks of folded paper products such as handkerchiefs or the like with blanks of plastic film, comprising at least one pocket (58), insertion means (5), along an insertion direction, of a single stack in said pocket (58) with the interposition and consequent folding of a corresponding blank, said pocket (58) being operatively associated with stop means (24) of the stack completely inserted within said pocket. There are control means (22) adapted to operate the stop means (24) in a coordinated manner with respect to the operation of the insertion means (5), to provide an abutment to the stack during the whole insertion step in the pocket (58), the stop means (24) comprising suction means (72) adapted to keep the film in position and to disengage the same film at least in an extraction step of the stack from the pocket.

Description

TITLE

UNIT AND METHOD FOR FEEDING FOLDED TISSUE PRODUCTS OR THE LIKE IN A REVOLVING DRUM PACKAGING MACHINE

DESCRIPTION

Technical field of the invention

The present invention concerns the packaging of stacks of folded tissue items such as handkerchiefs, napkins and the like with a wrapper made from weidable plastic film, for example but not exclusively through revolving drum machines.

Background of the invention

Known machines or apparatuses of this type are of the kind described in US patents US4845924 and US5459979. In brief, these are high speed packaging machines, comprising a drum provided with radial pockets with dimensions that are suitable for the product to be packaged, inside which the stacks of product to be packaged are inserted in rapid succession, with the simultaneous interposition of one blank plastic film, so as to obtain the complete wrapping of each stack, completed by welding applied on the film to obtain a closed packaging.

In machines of this kind, due to the high operation speed that is required to ensure suitable productivity, it is very complex to compress the stack, keep its correct geometry and carry out the insertion inside the pockets of the drum without causing deformations or faults in the wrapping by the film. In particular, but not exclusively, it is difficult, if not impossible, to keep control of the position of the film and of the compression in the radial direction of insertion during the wrapping step when the speed increases beyond a certain limit, causing defects in the package which, in any case, can occur also when the speed is kept below said limit.

Summary of the invention

There is thus the problem of feeding stacks of paper tissue products that can be compressed in packaging machines like those of the aforementioned type, exceeding the productivity limits currently imposed by the prior art, keeping the correct geometry of the group or stack of products, as well as the control of the compression (in the radial insertion direction) and of the position of the film in the wrapping step, all with constructive solutions that are relatively simple and reliable. The solution of such a problem is achieved with the unit and method according to the present invention, the essential characteristics of which are defined by the first and by the thirteenth of the attached claims.

Brief description of the drawings

The characteristics and the advantages of the unit and method according to the present invention shall become apparent from the following description of an embodiment thereof, given as an example and not for limiting purposes, with reference to the attached drawings, in which::

figure 1 is a schematic side view of a packaging machine according to the invention, complete with all its devices;

figure 1a represents an enlarged view of the zone that is circumscribed by the circle I of figure 1 , with parts removed for the sake of clarity of the illustration;

figure 2 is a schematic top plan view of the machine of figure 1 ;

figure 3 is a schematic side view like that of figure 1 but showing only the devices for feeding, compressing and inserting the stacks and the packaging drum;

figure 4 and figure 5 are respectively side and top plan views of an upper oscillating arm of the feeding device of the machine of the previous figures;

figure 6 and figure 7 are respectively a side and a top plan view of a lower oscillating arm of the feeding device of the machine of the previous figures;

- figure 8 is a cross-section view of the feeding device, with the upper and lower arms that are sectioned respectively along section lines B and A of figures 4 and 6;

figure 9 schematically depicts the movements of the upper oscillating arm of the feeding device in the various operating steps, in side view;

- figure 10 and figure 11 are respectively a top plan and front schematic view of a device for inserting the film and extracting the products;

figures 12 and 13 are respectively a side view and a front view of a stop plate cooperating with the device according to the two previous figures;

figures 14, 15 and 16 are respectively a schematic side view, a schematic top plan view and a schematic front view of the device for feeding the stacked products, with vertical product inlet; figure 17 and figure 18 are a side view and a front view of a feeder cylinder of the stacks of products, belonging to the feeding device according to the previous figures;

figure 19 is a schematic side view of the stack feeding device with a horizontal product inlet;

figures from 20a to 20g are side views of the packaging machine according to the invention in the various operating steps, from the insertion of a stack of products into the compression device to the outlet of the packaged products.

Detailed description of the invention

With reference to said figures, and in particular to figures 1 , 1a and 3, a packaging machine or apparatus according to the invention comprises a device 1 for inserting the product (stacks 3 of folded products to be packaged) into a feeding system. A couple of belts 2, coming from a folding machine upstream, feed the product to the inserting device 1 , along a direction that is orthogonal to the drawing sheet, taking here as a reference the way the machine is displayed in the figures.

A device generally indicated with reference numeral 4 is intended for feeding the stacks 3 to a compression device or system 8. The feeding occurs along a plane 35 that is inclined with respect to the horizontal, typically by about 10°. Figure 3 particularly shows belts 50 for the pre-compression and the feeding of the stacks 3 in the device 4, a couple of deviation rollers 52 of the belts 50 that can be adjusted in height as a function of the product to be packaged, and a stack 3 of products that have been pre-com pressed in the insertion step into a compression device 8 arranged downstream.

It can also be noted the provision of: a device 5 for the radial insertion of the stacks 3 in a packaging drum 21 equipped with pockets 58 radially formed with an adjustable width as a function of the product to be packaged; an upper oscillating arm 6 for the insertion of the stacks in the drum 21 ; and a lower oscillating arm 7 that slidably supports, along its axis, the aforementioned device 8 for compressing the stacks comprising a lower compression plate 9 with a reciprocating motion in a direction that is orthogonal with respect to the axis of the arm 7. A front plate 10 for stopping the stacks 3 is in turn reciprocating along a direction orthogonal to that of the lower arm 7, when it is in the position of bottom dead centre, in this case independently from the same arm. A support 11 of the stop plate 10 is indeed fixedly connected through a linkage 34a to a basement 34 of the machine (see figure 2).

A multiple cam upper actuation device 12 drives: a first crank and rod upper device 13 for controlling the insertion device 5 of the stacks 3, i.e. to displace the device 5 along the arm 6; a second crank and rod upper device 14 for radially controlling a mobile cam portion 22 intended also, as made clearer hereafter, for inserting the plastic packaging film; and a third crank and rod upper device 15 for controlling the radial displacement, i.e. along the arm 7, of the device 8 for compressing the stacks.

A multiple cam lower actuation device 16 drives: a first crank and rod lower device 17 for controlling the lower compression plate 9 of the stacks 3; a second crank and rod lower device 18 for controlling the front stop plate 10 of the stacks 3; a third crank and rod lower device 19 for controlling the rotation of the lower oscillating arm 7; and a fourth crank and rod lower device 20 for controlling the rotation of the upper oscillating arm 6.

Both cam actuation devices actually provide for a mechanism that comprises an eccentrically rotating disc, peripherally defining a cam surface with which a crank comes tangentially into contact. The crank is hinged at an end, and contacts the cam surface at a crank intermediate point, so that the same crank is driven in oscillation, around the hinging point, in response to the rotation of the disc. The rods linking the cranks to the various controlled devices are in turn pivotally connected, respectively, to the same devices, and to the cranks in predetermined points comprised between the crank intermediate point of contact with the disc, and a free end of the crank, all with geometrical characteristics that are suitably set as a function of the mutually coordinated displacements to be carried out.

The already mentioned mobile cam portion 22 drives extractors 24 that are also designed for assisting the insertion of the film in the pockets 58. More precisely, the mobile portion 22 represents a radially displaceable end portion (as seen driven by the second upper device 14) of a fixed cam 23 evolving according to a curl around the axis of the drum on a side thereof. In practice, the fixed cam 23 of the invention does not run according to a ring, but rather like an open loop, the opening being defined by a circumferential and radial discontinuity (step-like discontinuity) in the film insertion area. The mobile portion 22 is indeed arranged in correspondence with such a discontinuity, and is displaceable radially between a radially external position (guide cam larger diameter) and a radially internal position (guide cam smaller diameter), said displacement driving accordingly the movement of the extractors. In an area 23a opposite the discontinuity, the fixed cam 23 then evolves in a continuous manner from the smaller to the larger diameter so as to drive the extractors 24 between a rearward displaced position and a radially extracted position for pushing the packaged stacks 3 out of the pockets 58. The outlet of the packages from the drum 21 is indicated with reference numeral 25, still in figure 1.

Again in figure 1 it is possible to identify a band of film 29 fed by a cylinder 30 in a continuous manner for packaging the product, and cut in blanks 38 by a cutting cylinder 31 bearing a blade 32; finally, a transversal welding system 39 welds the film once wrapped around the stacks 3.

With particular reference now to figure 2, a series of ducts 40 is formed in the drum 21 for the passage of the depression/suction exerted on the periphery of the same drum. The passages 40 are clearly visible and indicated also in figure 3; they communicate with a fixed manifold 33 that circumferentially runs along a certain arc, along which the depression must indeed be sequentially transmitted, drawn from an external vacuum source to the purpose of holding the packaging film. Respective bearings 41 carry out the function of a mechanical drive link with the extractors 24. A transmission shaft 42 connected to the drum 21 is actuated by a motor 43 which also drives a shaft 44 for controlling the film feeding and cutting system. The arms 6 and 7 are coupled with the shaft 42, but idle therewith, adjacent to one another on one side of the drum, and in the same way there is arranged the mentioned cam 23 which is integral with the base 34. The same motor 43 also transmits motion to: a shaft 45 for controlling the upper actuation device 12; a shaft 46 for controlling the lower actuation device 16; a shaft 47 for controlling the stack feeding device 4; and finally a shaft 48 for controlling the stack inserting device 1.

Going back to figure 3, reference numerals from 53 to 57 denote various geometrical reference elements for the operation of the machine, according to what shall become clearer further on in the present description. A plane 54 defines the middle of the height 53 of the stacks fed by the device 4, said plane being thus equidistant from the rollers 52, and at the same time the middle of the height or opening 56 of the compression device 8 in the step of maximum opening, during the insertion of the product, at the bottom dead centre of the lower arm 7. A plane 55 moreover corresponds to the middle of the height of compression in the condition of maximum compression and coincides with a diametral plane of the drum 21. The compression height, indicated with reference numeral 57, can of course be adjusted as a function of the product to be packaged.

With particular reference to the figures from 4 to 8, these show in greater detail the group of the upper and lower oscillating arms 6, 7 with the device 5 for the insertion of the stacks, in the form of a bar projecting sideways towards the drum from the upper arm 6 (arranged farthest outside), and the compression device 8 supported cantilevered, again towards the drum, by the lower arm 7 (arranged farthest inside, i.e. adjacent to the drum itself). Obviously, the extension of the arms 6 and 7 is such as to ensure that the devices 5 and 8 face onto the working surface of the drum, i.e. that in which the pockets are formed.

Again in such figures it can be noted a linkage 60 with the first crank and rod upper device 13, a linkage 61 with the fourth crank and rod lower device 20 for controlling the upper oscillating arm 6, a linkage 62 with the third crank and rod upper device 15 for controlling the stack compression device 8, a linkage 63 with the third crank and rod lower device 19 for controlling the lower oscillating arm 7, an upper compression plate 64 that can be adjusted as a function of the height of the pockets of the drum and of the stacks to be packaged, and finally a linkage 65 with the first crank and rod lower device 17 for controlling the reciprocating motion of the lower compression plate 9.

The movement of the upper oscillating arm 6 in the various operating steps is indeed schematised in figure 9, together with the various positions correspondingly taken up by the insertion device 5. As it will be made clearer in detail hereafter, the insertion device 5 moves in practice according to a revolution around the upper compression plate 64, in a continuous manner without any abrupt motion inversion that could limit the productive speed.

Figures 10 and 11 , on the other hand, show more clearly an extractor 24, which, as mentioned above, also performs the function of assisting the insertion of the film 38, with its own bearing 41. In such figures there can be noted a duct 71 and holes 72 open on a working surface, for the passage of the depression/suction, such a surface being defined by a head 24a which represents a stop against which the stacks come into abutment. Figures 12 and 13 are, on the other hand, isolated representations of the front stop plate 10 of the stacks 3, and it can be noted how it is in turn provided with holes 73 for the passage of the depression/suction.

Again considering in particular figures 1 and 3, a sequential valve 27 is formed in the drum 21 ; such valve is fixedly linked with the fixed cam 23 for controlling the depression on the side of insertion of the film. In practice, in the point where the film is fed on the drum 21 by means of the cylinder 31 , the aforementioned valve activates the suction exerted by the extractors 24, turning the suction off when the product has been inserted completely, or at about 3/4 of the complete insertion run.

A further sequential valve 26 is in the shape of a crown, which is fixedly connected to the shaft 42 with which the drum 21 is integral, and is activated at about 2/3 of the insertion step, as a result of the movement of the extractors 24. When the tail end of the extractors 24 abuts on the bottom of grooves defined by the crown valve 26, the depression exerted by the extractors themselves is turned off. In this way, before the insertion has been completed, due to the depression applied at this point on the end flaps of the blank of film 38 by only the passages 40 of the surface of the drum, there is a return effect of the same film towards the outside with consequent effect of close adhesion to the stack 3.

The valve 26, and in particular the bottom of the relative grooves, can have different diameters to control at which insertion depth one desires to turn the depression off. A depression chamber 28, which transmits the suction to the extractors 24, is fed by a vacuum source normally with values that are about double that applied to the manifold 33, this indeed to ensure a safe positioning of the film during the insertion step. With particular reference now to figures 14 to 18, a feeding device 4 with vertical inlet thus also comprises a series of stack conveyors 80 linked with a transmission system, a stack front stop plate 81 , a series of stack guides 82 for guiding the stacks in the insertion step, a series of belts 83 and 87 outside the periphery of a conveyor cylinder 85 which can rotate integrally with a shaft 89, a series of cavities 84 formed in the cylinder 85, a series of belts 86 inside the cylinder 85, and a plurality of rollers 88 for controlling and deviating the various belts. The groups of external belts, in each of which two or more belts evolve in parallel, thus include three successive series of external belts, i.e. belts 83 opposing the belts 86 along the portion of vertical or almost vertical inlet, for compressing the stacks so as to keep them in position and aligned, the belts 50 which transport the stacks along the outlet portion, and belts 87 in an intermediate deviation zone between the inlet portion and the outlet portion, so as to keep the stacks in position in the passage from the vertical position to the horizontal one, in adherence with the cylinder 85 from which they are driven.

In figure 19 an analogous feeding device with horizontal inlet of the product, according to an embodiment that is alternative to the previous one, has a simplified structure with a feeding cylinder 90 without cavities. In the case in which there is horizontal outlet of the stacks from the folding machine upstream, there is no need for cavities since the belt deviation angle is reduced.

With reference now also and in particular to figures 20a to 20g, the machine according to the invention operates in the following manner.

As mentioned, the machine can be arranged for vertical or horizontal feeding, and in any case for a good operation the insertion plane 35 must have a certain inclination with respect to the horizontal, descending towards the drum 21 and preferably equal to about 10°. In such a way the stacks 3, as shall be comprised more clearly hereafter, adhere to the front stop plate in perfectly perpendicular arrangement with respect to the plane defined by the lower compression plate 9.

Starting from the step shown in figures 1 , 14 and 20a, the product stacks 3 are fed by the belts 2, and at the end of their path they are inserted in the product guides 82 in adherence with the stop plate 81. The insertion feet 80 have a continuous vertical and horizontal movement with constant speed equal to that of the belts 83 and 86 driven by the cylinder 85 of the feeding device 4, said belts 83, 86 receiving each stack by engaging with it at opposite ends, and also carrying out a slight compression. The stacks in forward displacement movement reach the cavities 84 formed in the cylinder 85, and after the detachment from the belts 83 they are kept compressed towards the cylinder 85 through the further outer belts 87 which are driven by the same cylinder through friction with its surface. In such a way the correct peripheral speed is maintained without causing the stacks themselves to become deformed.

When the stacks come out from the cylinder 85, the belts 50 in cooperation with the internal belts 86 transport the stacks to their insertion in the compression device 8. The outlet rollers 52 of the belts 50 and 86, as already mentioned, have an adjustment system for keeping an equidistant position with respect to the middle plane 54 as a function of the height of the product to be packaged. The speed of the belts can vary according to the diameter of the cylinder 85 and to the number of cavities 84 present in the cylinder itself. The stacks in outlet from the belts 50, 86 have a compressed height that is about the same as that of the packaged product, and are inserted into the compression device 8 in its condition of maximum opening 56 at the bottom dead centre of the arm 7. Such a height 56 is normally 50% greater with respect to the height of the stacks in outlet from the belts 50, 86.

When it is inserted in the compression device (figure 20b) the stack expands and becomes adherent with the stop plate 10 which exerts a suction (holes 73) ensuring the perfect alignment with the plate itself even of the single folded sheets of paper, before the compression.

Figure 20c represents the beginning of the compression step. The arm 7 begins its ascending movement, with the compression plate 9 which, having a relative movement that is orthogonal with respect to the arm 7, arrives at the programmed height and compresses the stack in cooperation with the upper plate 64. Such a programmed height of course coincides with the height of the pockets 58 of the packaging drum 21 and is maintained until the stack is completely inserted inside the drum.

The front stop plate 10, in turn capable of a movement which is orthogonal with respect to the lower arm 7 in the lower end stop position, meanwhile reaches and then keeps its own lower end stop position. At this point the compression device linked to the arm 7 in the condition of maximum compression of the stack carries out a radial displacement along the axis of the same arm until it gets close to the drum 21

The upper arm 6, in the meantime, has begun and continued a descending step, rotating around the axis of the drum 21 , until it reaches the bottom dead centre; then the movement is reversed and an ascending step begins.

Passing on to figure 20d, the arms 6 and 7 have reached a mutual alignment position that is suitable for allowing the insertion of the stack in a pocket 58 of the drum 21 , and at this point the insertion device 5, with a radial movement, moves toward the drum until it abuts against the stack of compressed product. Once a position in which the distance from the periphery of the drum corresponds to the width of the stack has been reached, the mobile cam portion 22 also begins a radial movement, i.e. a rearward displacement, accompanying the product in a coordinated manner with the device 5, so as to keep it orderly secured on two opposite sides, until it has been completely inserted.

Figure 20e shows the insertion step of the stack 3 with the arms 6 and 7 that rotate in phase with one another and with one of the pockets 58 of the drum 21. The device 5 proceeds forwards until the stack 3 is completely inserted; in adherence with the stack, by means of the passages 40 connected to a depression source, a blank of film was previously interposed so as to carry out the wrapping, according to a conventional expedient but with some peculiar provisions of the present invention which will result clearer hereafter. The front stop plate 10 returns to its initial condition.

Passing on now to figure 20f, the upper arm 6 continues to rise towards the top dead centre, the insertion device 5 keeps its position closest to the drum 21 , and the arm 7 reaches its top dead centre. The compression device 8 carries out a radial abrupt movement away from the drum, until it returns to the starting position, so as to free the space between the upper compression plate 64 of the device 8 and the insertion device 5.

Finally, as can be seen in figure 20g, the lower arm 7 and the compression plate 9 carry out a return movement to the starting position so as to receive a new stack of products. The upper arm 6 arrives at the top dead centre and inverts its movement, whereas the insertion device begins its radial movement along the arm 6 so as to return to the starting position, without interfering, as already mentioned, with the upper compression plate 64 which, being part of the device 8, is already in position to receive a new stack 3. The drum 21 continues its rotation with constant speed, in a clockwise direction according to the representation of the figures, and a new packaging pocket 58 proceeds to the point in phase with the arms 6, 7. The system is ready for a new cycle.

Returning to follow the path of the stacks inside the drum 21 , it should be noted that the control of the stacks, with the film wound in the pockets, is also taken up by the extractors 24 which, due to the movement of the cam portion 22 in the area of insertion, move rearwards thus providing an inner side abutment accompanying the same stacks in their insertion displacement.

Moreover, the suction exerted by the extractors 24 contributes to keep the stack and the wrapping film in an orderly fashion. When the packet passes in correspondence with the welding system, it is welded and then expelled thanks to the ejection of its extractor driven by the evolution 23a of the cam 23 in the area diametrically opposed to that of insertion. The control of the suction/depression exerted by the extractors 24 is synchronised along the appropriate rotation angle of the drum, by means of the valves 26 and 27.

The invention offers then a plurality of advantages. The feeding system through belts, which can have variable speed according to the diameter of the drum, ensures a high feeding speed while keeping the phase control of the position of the product, with short insertion time of the stacks in the compression device, with respect to a chain system, due to its capability not to cause the product to slow down. There is also the possibility of vertically or horizontally feeding the stacks, with pre-compression of the stacks before the insertion in the actual compression device so as to limit the width of the movement of the arms 6 and 7, consequent constructive simplification.

The stack stop plate 10, fixedly connected to the basement, with its depression system, for perfectly aligning the stack itself, is in turn capable of ensuring a significant improvement of the insertion operations, for speed, precision and constructive optimisation. More generally speaking, the results achieved with the invention are due to the overall design (structure and kinematism) of the compression and insertion systems, with - among other things - precise control of the axial compression of the stack by means of the insertion device 5, in cooperation with the extractor 24 and the mobile cam portion 22. As mentioned, very important is the path control of the insertion device; such path is in practice a planetary revolution around the upper compression plate 64 (see figure 9 and figures from 20a to 20g. The motion is smooth and continuous, so that the cooperation between the insertion device and the compression plate 64 ensures a perfectly orderly arrangement of the product, with productive speeds that can be kept very high. More generally speaking, the extractor that accompanies the insertion of the stack with a precise position control of the film, via the connection to a depression source, represents a novel and extremely advantageous feature as far as the quality requirements of the packaging are concerned.

The vertical/horizontal spatial references used above are of course to be interpreted in relation with the most typical operative configuration, and to the orientation represented in the figures, but it is clear that they must not take up any limitative connotation.

The present invention has been described thus far with reference to its preferred embodiments. It should be understood that other embodiments can exist which pertain to the same inventive core, within the scope of protection of the attached claims.

Claims

1. A unit for compressing and inserting a sequence of stacks of tissue paper products or the like, from an upstream feeding system to a revolving drum for packaging stacks with blanks of plastic film, said unit comprising insertion means for inserting said stacks in said drum in a radial direction and compression means for compressing the stacks, preliminary to said insertion, in a direction substantially tangential of said drum, wherein said compression means and said insertion means are supported respectively by a lower arm and by an upper arm radially projecting from a rotation axis of said drum and arranged sideways to the same drum, said arms being tiltable in a reciprocating manner, independently one from each other and from the drum, around said axis, driving means being provided for driving, respectively, said insertion means, said compression means and said arms, in a coordinated manner with each other and with the rotation of said drum.

2. The unit according to claim 1 , wherein said insertion means comprise an insertion device slidable in a reciprocating manner along said upper arm for pushing said stacks towards said drum, and said compression means comprise a compression device in turn supported slidably and driven in a reciprocation manner along said lower arm, said driving means being adapted to drive the reciprocating motion of said compression device in a coordinated manner with the reciprocating motion of said insertion device, for avoiding mutual interference following to the tilting motion of said arms.

3. The unit according to claim 2, wherein said driving means are adapted to drive said insertion device and said compression device so that said insertion device is adapted to carry out a continuous closed loop motion around at least a portion of said compression device.

4. The unit according to claim 2 or 3, wherein said stack insertion device projects towards said drum from a side of said upper arm, arranged externally, and said compression device is supported cantileverly, still towards said drum, by said lower arm, arranged internally, that is close with the same drum, the radial extension of said arms being such that said insertion device and said compression device face a working surface of said drum.

5. The unit according to any of the claims from 2 to 4, further comprising a front stop plate for stopping the stacks when inserted within said compression device, said front stop plate being reciprocatingly movable, along a direction substantially orthogonal with said lower arm when the same is in a lower dead point, in an independent fashion with respect to the same arm, said plate being supported between the compression device and said drum by a support integral with a basement structure of said unit.

6. The unit according to claim 5, wherein in said lower dead point of said lower arm, corresponding to an insertion phase of said stacks in said compression device, said lower arm is inclined with respect to the horizontal direction, with a descending inclination toward said drum, preferably of about 10°.

7. The unit according to claim 5 or 6, wherein said front stop plate is associated with suction means for exerting a holding action of said stacks.

8. The unit according to any of the claims from 2 to 7, wherein said compression device comprises a lower plate movable in a reciprocating manner in a direction orthogonal with said lower arm, and a top fixed plate integral with said arm, at an adjustable distance therefrom, said insertion device being adapted to pass between said plates.

9. The unit according to claim 8, wherein said lower plate and said top plate are arranged so that a median plane of a stack with respect to its height in the maximum compression within said compression device lies in a diametrical plane of said drum.

10. The unit according to any of the previous claims, wherein said driving means comprise cam means comprising an eccentrically revolving disc, defining a cam surface contacted tangentially at an intermediate point by a crank hinged at an end, thereby a tilting of said crank is driven around the hinge point as a result of the rotation of said disc, the driving means further comprising linking rods for driving the respective devices, said rods being hinged respectively to the devices and to said crank at predetermined points comprised between the disc contacting point and a free end of the crank, opposed to the hinged end.

11. The unit according to claim 8 or 9, wherein said driving means comprise cam means comprising an eccentrically revolving disc, defining a cam surface contacted tangentially at an intermediate point by a crank hinged at an end, thereby a tilting of said crank is driven around the hinge point as a result of the rotation of said disc, the driving means further comprising linking rods for driving the respective devices, said rods being hinged respectively to the devices and to said crank at predetermined points comprised between the disc contacting point and a free end of the crank, opposed to the hinged end.

12 The unit according to claim 11 , wherein said driving means comprise a multiple cam upper driving device adapted to control an upper crank and rod device for radially driving said insertion device, and a further upper crank and rod device for radially driving said compression device, said driving means further comprising a lower multiple cam driving device adapted to control a first lower crank and rod device for driving said lower compression plate, a second lower rod and crank device for driving said front stop plate of the stacks, a third lower rod and crank device for driving the rotation of said lower tilting arm, and a fourth lower rod and crank device for driving the rotation of said upper tilting arm.

13. A compression and insertion method for inserting a stack of folded products by means of a unit according to claim 1 , comprising the following steps:

- inserting a stack in said compression device with said lower arm in a lower dead end position;

- lifting said lower arm and operating the compression of the product by said compression device;

- radially forward displacing said compression device towards said drum and positioning said upper arm in a substantial alignment with said lower arm;

- radially forward displacing said insertion device towards said drum;

- pivotally lifting said arms, in phase with the rotation of said drum during the insertion of said stack in said drum, until a radial forward displacement run of the insertion device is completed;

- reversing the motion of said lower arm, further lifting said upper arm, with the insertion device in a maximum forward displacement position close to the drum, and rearward displacing said compression device in order to avoid interference with said insertion device; - returning said lower arm towards the lower dead end, reversing the motion of said upper arm and returning said insertion device by radial rearward displacement.

14. The method according to claim 13, wherein in the insertion step of said stack in said compression device, the same stack frontally abuts on a stop which is driven independently and in a coordinated manner with respect to said lower arm.

15. The method according to claim 13 or 14, wherein said insertion means carry out a continuous loop revolution around at least a portion of said compression means.

16. The method according to any of the claims from 13 to 15, wherein a median plane of a stack with respect to its height in the maximum compression within said compression device, during said phased rotation of said arms, lies in a diametrical plane of said drum.