EP3353073A1

EP3353073A1 - Ring wrapping machine

Info

Publication number: EP3353073A1
Application number: EP16794416.4A
Authority: EP
Inventors: Massimiliano Ubertini
Original assignee: Messersi Packaging Srl
Current assignee: Messersi Packaging Srl
Priority date: 2015-09-25
Filing date: 2016-09-22
Publication date: 2018-08-01
Also published as: WO2017051343A1

Abstract

A ring wrapping machine is described, consisting of a frame (1) which carries a circular opening (3) within which the items to be wrapped are placed, comprising a delivery unit (9) for the application of a film (11) of plastic material to said items. Said delivery unit (9) is carried by an annular element (5), concentric to the circular opening (3), and placed outside of it, able to rotate around the common centre. Said delivery-unit (9) comprises an adjusting device of the delivery speed, controlled by the tension of the film (11) being delivered through a mechanical actuator (22; 18; 16). Preferably, the circular opening (3) consists of two concentric rings (4, 5), the ring (4) being fixed to the plane (2) which carries it and the ring (5) being capable of rotating, under the action of two pairs of driving wheels (6), actuated by a motor (7). The mechanical actuator comprises a lever (22), an arm (23) of which carries the transmission rollers (24, 25) for the film (11) to be applied,, so that the traction or the release exercised by the film (11) results in the movement of the arm (23), and the other arm (21) is connected to an arm (20) provided with bearings which pulls or pushes another arm (19) which, in turn, is apt to slide longitudinally in a wedge (18) adapted to rotate being pressed by the springs against the surface of said fixed ring (4).

Description

RING WRAPPING MACHINE

DESCRIPTION

The present invention relates to a ring wrapping machine, capable of applying a film of plastic material to an object or group of objects to be packaged, with speed and pre-stretching being automatically adjusted according to the contour^" of the object or group of objects.

One of the major problems that the industrial civilisation has had during its advancement is the transport of the products, once they have been produced. In particular, for the mass production the manner by which the goods are loaded on transport means is always very important, in order to rationalise the spaces within the means themselves and to allow the products to be moved in the simplest and most economical way, while seeking to minimise the possible damage.

This is particularly significant when multiple products of the same type are to be delivered simultaneously, for example to be sold together. An example of this is the mineral water or the beverages in general, that are retailed in six-bottle packs; to do this, the bottles are held together by a film of plastic material, which is pre-stretched and then applied and pulled to hold the bottles together in a sufficiently tight manner as not to lose any of them during the transport. This mode allows the creation of very compact items, minimising the voids within the lorries for. the transportation thereof. This system, described for the case of beverage bottles, is also used for many other products, which are often very different from the bottles.

There are different types of packaging. A good classification categorises them into primary, secondary and tertiary pack- aging.

A primary packaging is made so as to constitute a sales unit for the final consumer. For example, the primary packaging is the case of bottles, tins, packets, tins, boxes and so on.

In a secondary packaging multiple units of the same product can be grouped one another. Examples of secondary packaging are the aforementioned six-plastic bottle packs, the packs with three beer tins, the packs with four tins of peeled tomatoes, the bag containing six bags of potato chips, and so on.

A tertiary packaging consists of bringing together more primary and secondary packagings for the transport, so as to avoid the damage associated with their transportation and to allow an easy handling. Examples of tertiary packaging are boxes, bags, pallets and the like.

To create packaging, there are various known techniques and equipment .

One of the machines most commonly used in the industry is the wrapper. A wrapping machine pre- stretches a film of a suitable plastic material and places it on the item to be packaged by means of a film delivery unit, while maintaining it taut. The delivery unit releases the pre-stretched film around the items to be packaged at a certain speed, so as to completely wrap the item with the film itself, making one complete rotation. Cutting means then cut the film when it has completely wrapped the items. Since the stretching commonly applied in these cases is fundamentally elastic in nature, once completed the application the film tends to return to its original size, thus holding the components of the package packed tight one another, so as to avoid losing any of them.

The ring wrapping machine has proved particularly advantageous. In a machine of this type, the items to be packaged are placed inside a frame around the inner periphery of which the delivery unit is rotated around the item.

Machines of this type are extremely functional and allow to solve the above-mentioned problems with high efficacy. However, while these machines work fine for equal sized packs, they suf- fer from some problems when a sequential packaging of different sized items is desired. Indeed, after wrapping an item, if it is desired to wrap another one of different size, it is necessary to stop the machine, adjust the film dispensing speed in a different way according to the new item, and restart the wrapping. Obviously, this involves a not negligible increase of downtimes when the items to be packed are not all even and it is needed to wrap items of quite different sizes.

However, some problems can arise when the items to be wrapped, although having even sizes, have each an overall irregular shape; in such a case, it would be appropriate to vary the film delivering speed in a differentiated way, as the items are gradually wrapped, so as to ensure an even and optimal tension on the entire side surface of the item itself. This way prevents parts of the item (above all if it consists of different components) from slipping away from the wrapping, endangering its tightness and stability.

This problem has already been faced and brilliantly solved by the same Applicant who has perfected a ring wrapping machine for packaging products in a package with a film of plastic material dispensed from a reel. The wrapping machine comprises a frame with a central circular opening that leads to the electrically controlled delivery unit. The delivery unit rotates around the central opening releasing film on the item to be packaged. The wrapping machine moves owed to an electric motor present thereon. The speed adjustment is triggered by sensor means, which send control signals to the delivery unit.

This machine is extremely effective. However, it has the drawback of having different electrical connections; finally, the mechanical parts of the motor of the delivery unit tend to wear out rather quickly.

With her patent application WO2014/128 587, the Applicant solved the problem of bringing electricity to the delivering unit, triggering it via electric induction. By the same electric induction the release of the film took place.

If these solutions, both very brilliant, deliver very high performance, they feature the drawback of being rather expensive to realise.

EP 1 125 841 discloses a wrapping machine with support elements to support a film roller feeding a dispenser. The roller has bearings, therefore being free to rotate. Also the pre- stretch rollers are able to rotate by means of bearings. A compensation roller is carried by an oscillating lever arm, which causes the adjustment of the delivering through the tension of the film.

EP 0 811 554 discloses a ring wrapping machine wherein a dispensing device is able to rotate around said ring.

US 4 706 443 relates to a wrapping machine which operates at a constant tension of the film to be wrapped.

The problem underlying the invention is to propose a wrapping machine, which overcomes the above-mentioned drawbacks, which allows to avoid having electricity on the delivery unit, and which is able, at the same time, to adjust the delivering speed any time during the delivering process. This object is achieved through a ring wrapping machine, consisting of a frame which carries a circular opening within which the items to be wrapped are placed, comprising a delivery unit for the applica- tion of a film of plastic material to said items, said delivery unit being fastened to a first annular element and resting on another fixed annular element, concentric to the circular opening, said first annular element being able to rotate around the common centre and said delivery unit comprising an adjusting de- vice of the delivery speed, controlled by the tension of the film being delivered through a mechanical actuator, characterised in that said mechanical actuator comprises a lever (22), one arm of which (23) carries transmission rollers (24, 25) for the film (11) to be applied, so that the traction or the release imparted by the film (11) imply the movement of the arm (23) and the other arm (21) is connected to an arm (20) , provided with bearings which pulls or pushes another arm (19) which, in turn, is apt to cause a wedge (18) to slide longitudinally, said wedge being apt to rotate pushed by springs against the surface of said fixed ring (4) , due to the effect of the rotation of the ring (5) carrying the delivery unit (9) . The dependent claims describe preferred features of the invention.

Further features and advantages of the invention will anyhow be more apparent from the following detailed description of a preferred embodiment, given by mere way of non- limiting example and illustrated in the accompanying drawings, wherein: Figure 1 is a perspective view of a wrapping machine according to the present invention;

Figure 2 is a plan view of a part of the machine of Figure 1 showing the work area of the delivery unit;

Fig. 3 is a plan view, partially sectional, of a delivery unit for the wrapping machine of Fig. 1;

Fig. 4 represents a detail of the delivery unit of Fig. 3 while operating;

Fig. 5 shows the detail contained in circle V of Fig. 4 ; Fig. 6 is an enlarged, perspective view of the part of the delivery unit intended to adjust the pre-stretching of the plastic film with which to wrap an item through the wrapping machine of Fig. 1;

Figs. 7A and 7B are perspective views of the delivery unit of the wrapping machine of Fig. 1, viewed from two different directions ;

Fig. 8 shows the detail contained in circle VIII of Fig.

7A;

Fig. 9 shows the detail contained in circle IX of Fig. 7B; Fig. 10 shows a detail of the view of Fig. 2, highlighting the handling of the wrapping machine according to the present invention;

Fig. 11 is a side view of a detail of a delivery unit of the wrapping machine according to an alternative embodiment of the present invention;

Fig. 12 is a side, exploded view of a detail of Fig. 2 ; Fig. 13 is a side view of a component of the delivery unit of the wrapping machine, according to the present invention, according to a preferred embodiment;

Fig. 14 is a plan view of a detail of a delivery unit of the wrapping machine according to an alternative embodiment of the present invention; and

Fig. 15 is a side view of the detail of Fig. 14.

In a known way, a ring wrapping machine is

As can be clearly seen from the figures, the wrapping machine according to the present invention is a ring wrapping ma- chine . A ring wrapping machine as the machine of the present invention is represented in its entirety in Fig. 1.

The wrapping machine includes a frame 1, which has a shape of a parallelepiped or, more rarely, of a hollow cube. Inside the frame 1 there is a plane 2, the height of which can be adjusted if necessary, including internally a circular opening 3. The adjustable height of the plane 2 allows, on one side, to choose the area to be wrapped and, on the other, to obtain a spiral wrapped packaging on the whole side surface of an item.

The plane 2 is shown in greater detail in Fig. 2. As one can easily see, the circular opening 3 of the plane 2 is formed by two concentric rings 4 and 5. The ring 4 is fixed to the plane 2 which carries it and the ring 5, placed externally with respect to ring 4, is capable of rotating, under the action of two pairs of driving wheels 6, actuated by a motor 7. Although the configuration just disclosed is preferred, the inverse solution is also conceivable, wherein the ring 5, able to rotate, is placed internally with respect to the fixed ring 4. Preferably, the motor 7 which actuates the rotation of the wheels 6 is an electric motor. Advantageously, the wheels 6 are contained in a crankcase 8, fastened to the plane 2. In a particularly preferred manner, the crankcase 8 consists of two half-shells which are screwed around each wheel 6 and which keep said wheel in position due to springs compressed by the tightening of the screws closing the crankcase 8. This construction allows to maintain a good movement of the wheels 6, without waste of energy.

The ring 5 carries, fastened to it, a delivery unit 9 of a film of plastic material for the wrapping of the items. If the rotating ring is placed internally, the unit 9 will be turned to the opposite side, than is shown in the appended drawings.

The delivery unit 9 is illustrated in Figs. 3 to 9.

As can be schematically seen in Fig. 3, the unit 9 includes a reel 10, which carries the plastic film to be used. The film 11 passes through a roller 12 and a roller 13, which manage the pre- stretching. The rollers 12 and 13 are connected to a pair of gears 14, 15 which trigger them, adjusting their speed. The gears 14, 15 are in turn connected to a transmission rope 16 via an angular transmission. The rope 16 also regulates their movement. Preferably, the rope 16 is made of flexible steel or nylon, so as not to create a hitch, not to corrode and to transmit the motion in a particularly effective way. The other end of the transmission rope 16 is connected to an end of a small shaft 17. The other end of the small shaft 17 carries a rotating wedge 18. Preferably, the wedge 18 has the shape of a frustocone. The wedge 18 is pressed constantly against the ring surface 4 by suitable compression springs 27.

The wedge 18 is laterally integral to an arm 19 that adjusts the sliding movement towards the other end of the small shaft 17 and in the opposite direction. The arm 19 is connected, via another arm 20 perpendicular therewith, to an arm 21 of a lever 22. Preferably, the lever 21 is a rocking lever or dancing roller. The other arm 23 carries a pair of transmission rollers 24, 25, from which the film 11 of plastic material to be dispensed is passed. Advantageously, the arm 23 of the rocking lever 22 is connected to a return spring 26, fastened to the body of the delivery unit 9. The lever 22 is formed in one piece; therefore, the arms 21 and 23 are parts of the same piece.

In summary, said mechanical actuator comprises a lever 22, an arm 23 of which carries the transmission rollers 24, 25 for the film 11 to be applied, so that the traction or the release exercised by the film 11 results in the movement of the arm 23, and the other arm 21 is connected to an arm 20, provided with bearings which pulls or pushes another arm 19 which, in turn, is apt to make a wedge 18 slide longitudinally the wedge 18 being adapted to rotate and being pressed by the springs 27 against the surface of said fixed ring 4 due to the rotation of the ring 5 which carries the delivery unit 9.

According to an alternative embodiment of the present invention, the transmission rope 16 is connected to a torque lim- iter 28, of a type known per se . According to the embodiment shown in Figs. 11 and 12, the torque limiter 28 is connected to a free wheel 29, also of a type known per se . The free wheel 29 is connected to a small shaft 30, which, with an angular transmission 31, is connected to a shaft 32, in turn carrying a gear 14. The gear 14 is engaged with the other gears 15, 33, integral with the delivery rollers 12, 13 which adjust the degree of stretching of the film 11. The description is made by introducing also the free wheel 29, but a device that does not include it also falls, in any event, in the scope of the present invention.

According to a preferred embodiment of the present inven- tion -shown in Fig. 13-, the wedge 18 is carried by a base support 34, which carries two pairs of pins 235, apt to slide in a groove 36, in accordance with the direction of the double arrow F. Figure 13 depicts two positions of the wedge 18, one of the two positions being represented shaded and with the numbers with a superscript. The wedge 18 is held pressed against the fixed ring 4 with the right pressure, due to the loading spring 27.

The wedge 18 is laterally integral to an arm 19 that adjusts the sliding movement (in the embodiment of Fig. 13 within the groove 36), in the two directions.

The alternative embodiment, shown in Figs. 14 and 15, provides that the transmission rope 16 is replaced by a universal joint 37, comprising two universal joints 38, 39.

In the following the operation of the wrapping machine according to the present invention is shown.

An item to be packaged (not shown for clarity sake in the drawings) is introduced inside of the frame 1, by placing it at the centre of the circular opening 3. The item may be of any type. Normally, the machine according to the present invention is used for the secondary and tertiary packaging, while it ap- pears difficult (though not impossible nor discouraged) its use for a primary packaging.

The first operation consists in adjusting, in a known manner, the height of the plane 2, so that the application of the film 11 on the item takes place in zones of the latter that are optimal for the stability of the packed item and to avoid the loss of parts of the item itself during transportation. Once this preliminary operation is complete, the film 11 is supported with its free end to the item, in a manner to prevent the end from escaping during the application, and the release of the film 11 is started by the delivering unit 9, unwinding the film 11 from the reel 10. In a known manner, the delivering occurs by rotating the delivery unit 9 around the item, stretching the film before the exit from the delivering unit 9 and wrapping in this way the item with the film 11, until the enclosure of the packaging and the cutting of the film 11 itself.

According to the present invention, the rotation of the delivering unit 9 is carried out not by a direct rotation of the latter, as was the case according to the prior art, instead by rotating the ring 5 that carries it with respect to the fixed ring 4. The advantage of this configuration is to avoid the need for electricity on the unit 9 to move it around the item to be wrapped.

As already mentioned earlier, the rotation of the ring 5 is caused by the driving wheels 6. They are made to rotate by the motor 7, which controls its rotation to the desired speed. The drive wheels 6 wheels are made of rubber or similar material or coated with rubber or similar material; in this way, they have a very high friction coefficient, so that their rotation causes the rotation, practically at the same speed, of the ring 5, normally made of metal. In virtue of the embodiment described above of the wheels 6 with a crankcase 8 formed by two half-shells (with a shape similar to the drive wheel of the Vespa motorcycle) the wheels 6 are extremely stable, do not wobble in their rotational movement, so that unnecessary energy losses are avoided.

The winding of the film 11 to be wrapped around the item causes on the film 11 the creation of traction forces in the direction of the item. In particular, these forces act on the transmission rollers 24, 25; through them, the traction is then brought on the lever arm 23, by pulling or loosening it. The traction or release exerted on the lever arm 23 causes obviously a swing movement of the rocking lever 22 in one direction or in the opposite direction. In the following, we examine the two opposing possibilities.

Firstly, we examine the case in which the winding of the film 11 on the item causes an increased traction. In this case, the lever arm 23 moves in the direction of the arrow F (Fig. 3) . The rotation about the fulcrum causes the arm 21 to move in the opposite direction, pulling the arm 20. The arm 20 is like a plunger. It moves with its own drive the arm 19, which, in turn, moves the wedge 18 in the direction of the arrow FL (Fig. 3) . The movement of the wedge 18 takes place through the sliding of the small shaft 17, assisted by some bearings. As mentioned previously, the wedge 18 is held pressed by suitable springs against the ring surface 4. The rotation of the ring 5 relative to the ring 4 results in the rotation of the wedge 18, pressed against the fixed ring 4, due to the friction with the ring 4 itself. In the situation just described, its traction in the direction of the arrow FL causes the wedge to be moved so as to remain in contact with the ring 4 with the narrower part of diameter. In this way, the speed of rotation of the small shaft 17 increases, but the speed of rotation of the ring 5 does not. This rotation is transmitted to the transmission rope 16 or to the universal joint 37, which, owed to the angular transmission 31, transmits the movement to the gears 14, 15 so that they accelerate the rotation of the rollers 12, 13. In this way, as a result of the greater traction exerted on the film 11, the delivering speed is increased. The delivering speed, which can be reached in this manner, can ensure that the length of the film reaches up to 250% of the original one, without particular problems. In this step, the return spring 26, opposing the movement of the arm 23 in the direction of the arrow F, prevents the wedge 18, owed to the effect of its rotation on the ring 4, to engage the ring 4 itself, after a few turns, with its part having the smaller diameter, so that even a low traction ensures, after a short time, to reach always and in any case the maximum delivering speed.

Now the case in which the tensile force on the film 11 de- creases in the course of the winding is described. In this case, the transmission rollers 24, 25 are released. This causes the lever arm 23 to be moved in the direction of the arrow P (Fig. 3) , due to the return action exerted on the arm 23 by the return spring 26. The lever 22 swings around its own fulcrum, and the arm 21 moves in the opposite direction to that of the arm 23, pushing the arm 20 and, consequently, the arm 19. In this way, the wedge 18 moves in the direction of the arrow A. The consequence of this movement is that the wedge 18 remains in contact with the ring 4 with its part having a larger diameter. In this way, the rotation transmitted by the wedge 18 to the small shaft 17 occurs at a more reduced speed, also without variations in the speed of rotation of the ring 5. This also decreases the speed of rotation of the transmission rope 16. This deceleration is transmitted, through the angular transmission, to the gears 14, 15. In this way, the speed of rotation of the rollers 12, 13 is also reduced, so as to decrease the delivering speed of the film 11.

From the above, it can be said that said wedge 18 is car- ried integrally by a small shaft 17 which rotates therewith and which, in turn, transmits the movement thereof to a transmission rope 16 which, owed to an angular transmission, in turn transmits said movement to gears 14, 15 which control the movement of rollers 12, 13, apt to adjust the pre-stretching of the film (11).

During delivering of the film 11, especially when items of very irregular shape are packaged, the two situations just described alternate continuously, ensuring a continuous adaptation of the delivery speed of the film 11 at the particular point of the packaging. This action has a macroscopic and a microscopic effect .

The macroscopic effect is the possibility, thanks to the wrapping machine according to the present invention, of using the machine with a series of items, different from one another, without having to stop the machine to adjust the delivering speed of the film 11 and without varying the winding speed of the items.

The microscopic effect is of a point -by-point adaptation of the pre-stretching of the film on the same item, so that the final packaging is optimum everywhere, because on all the points to which it has been applied the same strength of containment is exerted, with enormous advantages in terms of integrity of the packaging, less risk of breakage in the items, and elimination of the risk of losing part of the contents of packaged items. The alternative embodiment, shown in Figs. 11 and 12, allows solving some additional problems. In fact, if the film 11, due to the fast rotation, creates a tangling between the rollers 12 and 13, there is an increase of the resistance to rotation of the transmission rope 16 or of the universal joint 37. When this resistance exceeds a preset threshold value, the torque limiter 28 intervenes and causes the movement of the wedge 18 to be no longer transmitted to the rope 16 or universal joint 37, putting itself in idle status. In this way, without the need to stop the rotation of the ring 5 and, consequently, of the wedge 18, the delivering stops. The wrapping machine may comprise, in addi- tion, other safety devices, which cause the stop of the rotation of the ring 5 when the small shaft 17 rotates idle, driven in rotation by the wedge 18, with respect to the transmission rope 16 or to the universal joint 37. The healing of the situation and the restore of the original conditions can thus proceed without disadvantages and in particularly fast times.

According to a preferred embodiment of the present invention, shown in particular in Fig. 13 (but always referring also to Fig. 3) , the oscillation of the arm 19 in the direction of the arrow FL (Fig. 3) , causes the pins 35 to slide in the slot 36, until they reach the position indicated by the reference numerals 18 ' , 34 ' , 35¹.

Now, the case in which the tensile force on the film 11 decreases in the course of the winding is described. In this case, the transmission rollers 24, 25 are released. This causes the lever arm 23 to be moved in the direction of the arrow P (Fig. 3) , due to the return action exerted on the arm 23 by the return spring 26. The lever 22 oscillates around its own fulcrum, and the arm 21 moves in the opposite direction to that of the arm 23, pushing the arm 20 and, consequently, the arm 19. In this way, the wedge 18 moves in the direction of the arrow A. In the case shown in Fig. 13, there is the sliding of the pins 35 in the opposite direction to that seen previously, and the wedge 18 tends to assume the position shown by the reference numerals 18, 34, 35. As a result of this movement, the wedge 18 remains in contact with the ring 4 with its part having a larger diameter. In this way, the rotation transmitted by the wedge 18 to the small shaft 17 occurs at more reduced speed, also without variations in the speed of rotation of the ring 5. This also decreases the speed of rotation of the transmission rope 16 or of the universal joint 37. This deceleration is transmitted, through the angular transmission, to the gears 15, 33, due to the rotation of the gear 14. In this way, the speed of rotation of the rollers 12, 13 is also reduced, so as to decrease the delivering speed of the film 11. Also in this case, the possible presence of the torque limiter 28 has the effect of reducing the negative consequences of a jam of the film 11 in the rollers 12, 13 or elsewhere .

From the above, it can be said that said wedge 18 is carried integrally by a small shaft 17 which rotates therewith and which, in turn, transmits the movement thereof to a transmissions rope 16 or to a universal joint 37 which, owed to an angular transmission 31, in turn transmits said movement to gears 15, 33, through the gear 14, which controls the movement of rollers 12, 13, apt to adjust the pre- stretching of the film (11).

The wrapping machine according to the present invention allows to produce a wide range of advantages, compared to the machines of the prior art, already used in the field.

First, electricity is only necessary in the (fixed) zone where the motors driving the drive wheels 6 are located. The rest of the components move in a purely mechanical manner. In particular, the adjustment of the pre-stretching of the film 11 takes place in a purely mechanical way. Therefore, there are no electrical equipment in the moving parts. This means that there are no significant phenomena of wear on the components of the delivery unit 9. Indeed, the only wear phenomena are related to the wheels 6 and the wedge 18. Both the wedge 18 and the wheels 6 are components of very moderate cost, which do not affect heavily on the maintenance costs of this machine. As regards the wedge 18, it is easily accessible, and its replacement is within the reach of any not necessarily skilled person. As regards, in- stead, the wheels 6, the construction of their crankcase 8 is extremely simple and with few tools, accessible to anyone, the crankcase 8 can be disassembled, for example by unscrewing, the wheel 6 can be replaced, the crankcase 8 can be closed, and the screws that hold it closed into place can be re-tighten. The wheel 6 is of a commercial type and can be easily found on the market .

As seen previously, the height of the plane 2 which carries the fixed 4 and rotating 5 rings can be adjusted. Advantageously, the height adjustment of the position of the plane 2 allows the wrapping machine according to the present invention to perform a spiral packaging, both starting from the bottom to get to the top of the item and in the reverse sequence .

Therefore, the wrapping machine according to the present invention allows, with performance similar to that of machines with electrical delivery unit, to obtain a less expensive construction, with minor need for maintenance and replacement of worn parts. The maintenance, moreover, is extremely simple -as has been said previously, even to the reach of not specialised personnel- since there are no warm contacts, or belts to re- place, the replacement of which requires machine downtime of whole days and highly specialised personnel.

The wrapping machine according to the present invention allows to obtain remarkable advantages, also compared to machines with mechanically controlled delivery units, but by means of transmission belts, as these do not allow the adaptation to the size and shape of the items, nor can compensate for any misa- lignment between the rings 4 and 5, wherein such compensation can instead take place in the machine according to the present invention, owed to the use of the lever 22.

Providing the torque limiter 28 -according to an alterna- tive embodiment of the present invention- allows to prevent any jamming of the film 11 during the delivery from leads to excessive damage, due to the loss of material and difficulties in restoring the original situation. This results in significant operational advantages and considerable savings of time.

The possible provision of a free wheel 29 -according to a preferred embodiment of the present invention- has also considerable advantages in the final stage of the wrapping of an item and in the switch to a subsequent item, in the initial stages of its wrapping. As mentioned in the introduction to the present description, at the time of cutting of the film 26 after the completion of the wrapping, a gripper grips the film 26 and, after having cut it, holds it and then bring it to the new item when also this should be packed. In this circumstance,, as stated above, the film is kept stretched to the maximum, and sometimes may even yield, or start to do so; also a reverse operation of the delivery unit does not loosen the tension, as it leads to a recovery of the film, keeping it in the same state of tension, since the rotation of the wedge 18 will rotate in the opposite direction also the rollers 12, 13 and the reel 10. The provision of the free wheel 29, after the gripper has gripped the end formed on the film 11 after the cutting, proceeding to a short section of travel (also pushing by hand) backwards of the ring 5, avoid the recovery of the stretched film and any loosening of the film 11 itself. In this way, the yield is surely avoided, and it is possible to adjust the initial tension of the film at the time of its application to the new item.

Finally, the use of a wedge 18 according to the embodiment of Fig. 13 can avoid the use of springs that maintain the wedge 18 pressed against the ring 4. The wedge 18 is preloaded to an optimum pressure at installation, and there is no need to vary the pressure in the delivery, since the sliding of the pins 35 into the groove 36 allows to bring the desired section of the wedge 18 wherever maintaining the same pressure and without the risk that the wedge 18 can escape during its rotation. In addition to avoiding the use of additional compression springs -with a certain saving in the realisation of the machine- it is avoided that the wedge 18 escapes during its rotation (which happens if the compression springs are too weak) and/or slows down the wear of its side surface, extending its life, resulting in a saving of material and machine downtime for replacement.

In this manner, the machine of the present invention solves brilliantly all the problems it addresses.

It is understood, however, that the invention is not to be considered as limited by the particular arrangement illustrated above, which represents only an exemplary embodiment of the same, but different variants are possible, all within the reach of a person skilled in the art, without departing from the scope of the invention itself, as defined by the following claims.

LIST OF REFERENCE NUMERALS

1 Frame

2 Plane

3 Circular opening (of 2

4 Fixed ring (of 2)

5 Mobile Ring (of 2)

6 Driven wheels (of 5)

7 Motor (of 6)

8 Crankcase (of 6)

9 Delivery unit

10 Reel (of 11)

11 Film

12 Roller

13 Roller

14 Gear

15 Gear

16 Transmission rope

17 Small shaft

18 Rotating wedge

18 ' Rotating wedge

19 Arm

20 Arm

21 Lever arm (of 22)

22 Lever

23 Lever arm (of 22)

24 Transmission roller

25 Transmission roller

26 Return spring

27 Spring

28 Torque limiter (of 16)

29 Free wheel (of 16)

30 Small shaft

31 Angular transmission

32 Small shaft

33 Gear Support (of 18) ' Support (of 18)

Pins

' Pins

Groove

Universal joint

Cardan shaft (of

Claims

1) Ring wrapping machine, consisting of a frame (1) which carries a circular opening (3) within which the items to be wrapped are placed, comprising a delivery unit (9) for the application of a film (11) of plastic material to said items, said delivery unit (9) being fastened to a first annular element (5) and resting on another fixed annular element (4) , concentric to the circular opening (3), said first annular element (5) being able to rotate around the common centre and said delivery unit (9) comprising an adjusting device of the delivery speed, controlled by the tension of the film (11) being delivered through a mechanical actuator (22; 18; 16), characterised in that said mechanical actuator comprises a lever (22) , one arm of which (23) carries transmission rollers (24, 25) for the film (11) to be applied, so that the traction or the release imparted by the film (11) imply the movement of the arm (23) and the other arm (21) is connected to an arm (20) , provided with bearings which pulls or pushes another arm (19) which, in turn, is apt to cause a wedge (18) to slide longitudinally, said wedge being apt to rotate pushed by springs against the surface of said fixed ring (4) , due to the effect of the rotation of the ring (5) carrying the delivery unit (9) .

2) Wrapping machine as in 1) , characterised in that the circular opening (3) consists of two concentric rings (4, 5), the ring (4) being fixed to the plane (2) which carries it and the ring (5) being capable of rotating, under the action of two pairs of driving wheels (6) , actuated by a motor (7) .

3) Wrapping machine as in 2), characterised in that said driving wheels (6) are rubber wheels or wheels of a similar ma- terial or are coated with rubber or with a similar material.

4) Wrapping machine as in 2) or in 3 ) , characterised in that the wheels (6) are contained in a crankcase (8) , fastened to the plane (2) and consisting of two half-shells which are screwed around each wheel (6) and which keep said wheel in posi- tion, due to the tightening of the screws closing the crankcase (8) .

5) Wrapping machine as in 5) , characterised in that one arm (23) of the lever (22) is connected to a return spring (26), fastened to the body of the delivery unit (9) .

6) Wrapping machine as in 5) or in 6) , characterised in that said wedge (18) is carried integrally by a shaft (17) which rotates therewith and which, in turn, transmits the movement thereof to a transmission rope (16) which, owed to an angular transmission, in turn transmits said movement to gears (14, 15) which control the movement of rollers (12, 13), apt to adjust the delivery rate of the film (11) .

7) Wrapping machine as in 5) or in 6) , characterised in that said wedge (18) is carried integrally by a shaft (17) which rotates therewith and which, in turn, transmits the movement thereof to an universal joint (37) which, owed to an angular transmission, in turn transmits said movement to gears (14, 15) which control the movement of rollers (12, 13), apt to adjust the delivery rate of the film (11) .

8) Wrapping machine as in 7) , characterised in that said transmission rope (16) is made of flexible steel or of nylon.

9) Wrapping machine as in any one of the preceding claims, characterised in that the ring (5) capable of rotating is found outside with respect to the fixed ring (4) .

10) Wrapping machine as in any one of claims 1) to 9) , characterised in that the ring (5) capable of rotating is found inside with respect to the fixed ring (4) .

11) Wrapping machine as in any one of the preceding claims, characterised in that a torque limiter device (28) is placed between said shaft (17) and said transmission (16; 37).

12) Wrapping machine as in any one of the preceding claims, characterised in that the torque limiter (28) is connected to a free wheel (29) .

13) Wrapping machine as _; in any one of the preceding claims, characterised in that the wedge (18) is carried by a base support (34) , which carries two pairs of pins (35) , able to slide in a groove (36) .

14) Wrapping machine as in any one of the preceding claims, characterised in that it comprises, furthermore, safety devices which cause the stop of the rotation of the ring (5) , when the shaft (17) rotates idle, driven in rotation by the wedge (18), with respect to the transmission (16; 37).