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Patent Searching and Data


Title:
FILM SUPPLYING APPARATUS FOR A WRAPPING MACHINE
Document Type and Number:
WIPO Patent Application WO/2019/077541
Kind Code:
A1
Abstract:
A supplying apparatus (1) of a stretchable plastics film (50), associable to a wrapping machine to provide a wrapping unit thereof with portions (51) of fixed length of film (50) with which to wrap single or grouped products, comprises unwinding means (2) to unwind the film (50) from a reel (55) and convey it out toward the wrapping unit of the wrapping machine; cutting means (3) to cut the film (50) and separate from the latter the film portions (51) to be provided to the wrapping unit; blocking means (4) adjacent to the cutting means (3), positioned between the latter and the reel (55), arranged to stop and block the film (50) while it is being cut by the cutting means (3) and comprising a pressing element (8) and an abutting element (11); and a transferring arm (15) that is movable and arranged to grasp an initial flap (50a) of the film (50) generated by the cutting means (3) by cutting the film (50) and transferring the initial flap (50a) to the wrapping unit; the transferring arm (15) is provided with a first end (15a) comprising gripping means (12) for grasping the initial flap (50a) of the film (50) and the abutting element (11) against which the pressing element (8) stops and blocks the film.

Inventors:
CERE', Mauro (C/O Aetna Group S.p.A, Strada Provinciale Marecchia 59, Verucchio, 47826, IT)
Application Number:
IB2018/058091
Publication Date:
April 25, 2019
Filing Date:
October 18, 2018
Export Citation:
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Assignee:
AETNA GROUP S.P.A. (Strada Provinciale Marecchia 59, Verucchio, 47826, IT)
ROBOPAC S.P.A. (Via Fabrizio Da Montebello, 81Acquaviva - Gualdicciolo, 47892, SM)
International Classes:
B65H35/00; B65B41/12; B65H16/00
Domestic Patent References:
WO2004069705A12004-08-19
Foreign References:
US3213726A1965-10-26
US3776081A1973-12-04
Attorney, Agent or Firm:
CICCONETTI, Andrea (Accapi S.R.L, Via Garibaldi 3, Bologna, 40124, IT)
Download PDF:
Claims:
CLAIMS

1. Supplying apparatus (1) of a stretchable plastics film (50), associable to a wrapping machine to provide a wrapping unit thereof with portions (51) of fixed length of said film (50) with which to wrap single or grouped products, comprising:

- unwinding means (2) to unwind said film (50) from a respective reel (55) and convey said film portions (51) out towards said wrapping unit of said wrapping machine;

cutting means (3) to cut said film (50) and separate from the latter said film portions (51) to be provided to said wrapping unit;

- blocking means (4) adjacent to said cutting means (3), positioned between the latter and said reel (55) and arranged to stop and block said film (50) while it is being cut by said cutting means (3), said blocking means (4) comprising a pressing element (8) and an abutting element (11), said pressing element (8) being movable in an active position (A) wherein it stops and blocks said film (50) against said abutting element (11);

characterized in that it comprises a transferring arm (15) that is movable and arranged for grasping an initial flap (50a) of said film (50) generated by said cutting means (3) by cutting said film (50) and transferring said initial flap (50a) to said wrapping unit, said transferring arm (15) being equipped with a first end (15a) comprising said abutting element (11) and gripping means (12) to grasp said initial flap (50a) of said film (50).

2. Supplying apparatus (1) according to claim 1, wherein said transferring arm (15) is further equipped with a second end that is rotatably fixed to frame means (10) of said supplying apparatus (1).

3. Supplying apparatus (1) according to claim 1 or 2, wherein said transferring arm (15) is movable between a grasping position (P), wherein said first end (15a) is adjacent to said cutting means (3) to enable said pressing element (8) to abut said abutting element (11) in said active position (A) and/or to enable said gripping means (12) to grasp said initial flap (50a) of film, and a transfer position, wherein said first end (15a) is adjacent to said wrapping unit to enable said gripping means (12) to transfer said initial flap (50a) of film to the wrapping unit.

4. Supplying apparatus (1) according to any preceding claim, wherein said abutting element (11) is fixed to said first end (15a) of said transferring arm (15) and/or included in said gripping means (12).

5. Supplying apparatus (1) according to any preceding claim, wherein said pressing element (8) comprises an abutting portion (9) and is rotatably mounted on frame means (10) of said supplying apparatus (1), rotatably movable about a respective longitudinal axis between said active position (A) and an inactive position (B), wherein said abutting portion (9) is spaced apart from said abutting element (11) and from said film (50), said abutting portion (9) and said abutting element (11) having a length equal to or greater than a width of said film (50).

6. Supplying apparatus (1) according to any preceding claim, wherein said cutting means comprises a cutting roller (3), rotating about a respective longitudinal axis and transversely to a feeding direction (F) of said film and provided with a longitudinal blade (7) adapted to cut said film (50), said blade (7) having a length equal to or greater than a width of said film (50).

7. Supplying apparatus (1) according to claim 6, comprising first driving means (41) to rotate said cutting roller (3) and motion transmission means (22) arranged to connect said pressing element (8) to said cutting roller (3) so as to rotate said pressing element

(8) in coordination with said cutting roller (3).

8. Supplying apparatus (1) according to claim 7, wherein said motion transmission means comprises a cam-lifter system (22).

9. Supplying apparatus (1) according to any claim 1 to 6, comprising first driving means (41) to rotate said cutting roller (3) and further driving means to rotate said pressing element (8) in coordination with the cutting roller (6).

10. Supplying apparatus (1) according to any preceding claim, wherein said unwinding means (2) comprises a couple of pre- stretching rollers (31, 32), positioned between said blocking means (4) and said reel (55) and arranged to unwind said film (50) from the latter and to stretch said film (50) for a fixed amount, and at least one tensing roller

(36) positioned downstream of said cutting means (3), with reference to a feeding direction (F) of said film (50), and arranged to keep said film (50) exiting said pre- stretching rollers (31, 32) under tension.

11. Wrapping machine for wrapping single or grouped products with a stretchable plastics film, comprising a film supplying apparatus (1) according to any preceding claim.

Description:
Film supplying apparatus for a wrapping machine

The present invention relates to apparatuses for supplying a wrapping film which can be installed on wrapping machines for supplying the latter with portions of a stretchable plastics film of predetermined length unwound from a reel and used to wrap single or grouped products.

The known wrapping machines operating with a cold-stretchable plastics film generally comprise an unwinding unit which houses and supports a film reel and moving means that supports and moves said wrapping unit. The film is unwound from the reel and wrapped around the load in order to form a series of strips or bands that are interwoven by the combination of a movement of the unwinding unit in a vertical direction and of the relative rotation between the unwinding unit and the load.

In addition to receiving and supporting the film reel, the unwinding unit is provided with a couple of pre- stretching rollers, which unwind the film from the roll and elastically and/or plastically stretch or lengthen it for a predetermined percentage in relation to the load to be wrapped, and one or more idle rollers that deviate the film toward the product or group of products.

In turntable wrapping machines the moving means comprises a strut or column along which a carriage supporting the unwinding unit moves vertically. The load is positioned on the turntable and rotates with the latter about a vertical winding axis.

In wrapping machines with horizontal rotating ring or rotating arm, the load remains fixed during wrapping, while the unwinding unit is moved around the load, both rotating about the vertical wrapping axis and moving along the latter.

In wrapping machines with vertical rotating ring, the load is moved linearly by suitable transporting means during the winding through the ring, while the moving means comprises a ring rotating about a horizontal winding axis and supporting the unwinding unit.

In these types of wrapping machines, the unwinding unit moves with respect to the load and the wrapping procedure performed provides an initial step wherein an initial flap of the film is approached to the load, a wrapping step wherein the first bands of film are overlapped over the initial flap to fix it to the load, and a final step wherein the film is cut, thus obtaining two flaps, one of which constitutes the tail end of the wrapping and is fixed to the load (for example welded or glued or inserted under pre-existing bands of film), while the other constitutes the initial flap of a subsequent wrapping and is retained by suitable grippers of the machine. The film cutting assembly can be associated with the unwinding unit or positioned at the load supporting structure (turntable, conveyor).

There are other known wrapping machines operating with cold-stretchable plastics film in which the film reel, the film pre-stretching and unwinding rollers and the cutting assembly are not supported and moved by the moving means, but are positioned on board machine on a fixed frame of the machine thereof to form an apparatus for supplying the film. The latter is in fact unwound from the reel, suitably pre-stretched and then cut by a cutting assembly such that the portions of film of predefined length are provided by the supplying apparatus to a wrapping unit of the machine, which provides for wrapping them around a product or group of products. More precisely, during wrapping, the supplying apparatus provides the film to the wrapping unit with a travel or turning speed that is linked to and depends on the winding speed of the film around the product or group of products.

The cutting of the film occurs when the latter is moving at the travel speed, as it is still wrapping around the load. In fact, by cutting the film, the end flap of the portion of film partially wrapped and being wrapped around the product or group of products is created along with the initial flap of a consecutive portion of film to subsequently be wrapped around another product or group of products. For this reason, while the film is being cut to deliver a portion of film of predefined length to be wrapped, the pre-stretching rollers and wrapping rollers are stopped so as not to deliver further film.

Suitable gripping means is provided in the supplying apparatus to retain the initial flap of the film produced by the cut and supply it to the wrapping unit of the machine at the start of a subsequent wrapping step.

The cutting assembly of the supplying apparatus typically includes a rotating cutting roller, provided with a longitudinal blade of a length at least equal to the width of the film to be cut, and a contrast roller, also rotating, provided with a longitudinal slot arranged for receiving the blade of the cutting roller. The contrast roller rotates in synchronism with the cutting roller so as to cut the film.

Considering that the film must be cut while it is still moving at the travel speed (as described above), in order to have a clean and precise cut the peripheral or tangential speed of the blade of the cutting roller must be equal to the travel speed of the film. In case the speeds are different, i.e., in the presence of a relative speed between the film and the blade, there is in fact a relative sliding of the blade on the stretchable film which causes the latter to fray or tear rather than to make a clean cut, due to the limited thickness and elasticity of the film itself. In this case portions of film are obtained which are unacceptable from an aesthetic point of view because they shows frayed and irregular edges, low precision and poor repeatability of the entire cutting operation are achieved, since the cut portions can have different lengths, and abnormal and excessive mechanical/structural stresses are generated on the blade that can compromise its longevity and correct operation.

During the operation of the supplying apparatus and the wrapping machine, when the portion of film must be cut, the cutting roller is driven with intermittent motion, more precisely rotated through a round angle (360°) at regular intervals. It is therefore necessary that, starting from an initial speed of zero (stopped cutting roller), at the halfway point of the round angle (180°) the cutting roller reaches its maximum rotation speed for which it has the desired tangential speed of the blade equal to the travel speed of the film. Similarly, the cutting roller must be stopped and blocked again at the halfway point of the round angle to avoid further cutting the film (thereby creating a portion of reduced length). This operation involves high acceleration and deceleration values which affect the cutting roller and the corresponding drive and moving means (motors, kinematic mechanisms).

One drawback of the known supplying apparatuses lies in the limited film travel speed with which they can operate, as with high film travel speeds (8-12 m/s), the cutting rollers must be subjected to high values of angular acceleration in order to have the necessary tangential speed of the blade, which are difficult or even impossible to obtain with the drive means (electric motors) currently available on the market. In other words, the speed or productivity of the film supplying apparatus, and therefore of the wrapping machine, are limited by the performance of the cutting assembly.

An object of the present invention is to improve the known supplying apparatuses as sociable to wrapping machines for supplying the latter ones with portions of fixed length of cold-stretchable plastics film with which to wrap single or grouped products.

Another object is to provide a supplying apparatus which will make it possible to deliver portions of predefined length of stretchable film to a wrapping unit of a wrapping machine at high speeds.

A further object is to provide a supplying apparatus capable of delivering, also at high speeds, portions of film cut in a precise and clean manner, without any fraying or tearing at the edges.

Another object is to provide a supplying apparatus equipped with robust and reliable cutting means able to make clean and precise cuts on the film.

Another further object is to provide a supplying apparatus having a strong and simple structure of reliable and safe operation.

These and still further objects are achieved by a wrapping machine according to one or more of the claims below.

The invention can be better understood and implemented with reference to the accompanying drawings that illustrate certain embodiments, by way of example and without limitation, wherein:

- figure 1 is a schematic sectional view of the supplying apparatus of the invention;

figure 2 is a partial, enlarged section of the apparatus of the invention showing the means for blocking the film arranged in an active position and cutting means acting on the plastics film;

figure 3 is a section similar to that of figure 2, illustrating the blocking means in an inactive position and the cutting means disengaged from the film;

figure 4 is a perspective and partially enlarged view of the supplying apparatus of figure 1;

With reference to figures 1 to 4, the supplying apparatus 1 of a stretchable plastics film 50 is shown according to the invention, associable to a wrapping machine to provide portions 51 of fixed length of said film 50 to a wrapping unit thereof, not shown, with which to wrap single or grouped products.

The supplying apparatus 1 includes unwinding means 2 to unwind the film 50 from a reel 55 and convey the film portions 51 out toward the wrapping unit of the wrapping machine, and cutting means 3 to cut the film 50 and separate from the latter the aforesaid film portions 51 to be provided to said wrapping unit.

The supplying apparatus 1 also comprises blocking means 4 arranged adjacent to the cutting means 3, positioned between the latter and the film reel 55 and arranged to stop and block the film 50 while it is being cut by the cutting means 3.

The blocking means 4 comprises a pressing element 8 and an abutting element 11; the pressing element 8 is movable in an active position A wherein it stops and blocks the film 50 against the abutting element 11.

The pressing element 8 comprises an abutting portion 9 and is rotatably mounted on frame means or frame 10 of the supplying apparatus 1, rotatably movable about a respective longitudinal axis between the active position A, wherein the abutting portion 9 blocks the film 50 against the abutting element 11, and an inactive position B wherein the abutting portion 9 is spaced apart from the abutting element 11 and from the film 50. The abutting portion 9 of the pressing element 8 and the abutting element 11 have a length equal to or greater than the width of the film 50 and extend in a transverse direction, in particular orthogonal to a feeding direction F of the film 50 in the supplying apparatus 1. With reference to the embodiment illustrated in the figures, the pressing element 8 includes a supporting shaft 18, mounted on the frame 10 and rotatable about a respective longitudinal axis and supporting at the opposite ends, by means of respective brackets 19, a transverse element 21 on which the abutting portion 9 having a flat shape is formed.

The cutting means comprises, for example, a cutting roller 3, rotating about a respective longitudinal axis and transversely to the feeding direction F of the film 50 and comprising a longitudinal blade 7 having a cutting profile adapted to cut or transversely shear the film 50 in a clean and precise way. The blade 7 is fixed to a supporting roller 6 of the cutting roller 3 so as to abut against the film 50 with a direction almost perpendicular to a plane defined by said film 50. The blade 7 has a length equal to or greater than the width of the film 50 and extends in a transverse direction, in particular orthogonal, to a feeding direction F of the film 50 in the supplying apparatus 1.

The supplying apparatus 1 comprises first driving means 41 to rotate the cutting roller 3 and motion transmission means 22 arranged to connect the pressing element 8 to the cutting roller 3 so as to rotate the pressing element 8 in coordination with the cutting roller 3.

In the illustrated embodiment, the motion transmission means 22 comprises, for example, a cam-lifter system 22 that makes it possible to use the continuous rotational motion of the cutting roller 3 in a partial rotation or oscillation movement of the pressing element 8 from the active position A to the inactive position B and vice versa.

More precisely, the cam-lifter system comprises two cam elements 23 positioned on both ends of the cutting roller 3, in particular of the supporting roller 6, and engaged by respective lifters 24 fixed to the respective ends of the pressing element 8. In particular, the lifters 24 are shaped appendixes of the brackets 19 that connect the supporting shaft 18 to the transverse element 21. The lifters 24 comprise respective rollers 25 that are kept in abutment against the moving profiles 23a of the cam elements 23 through elastic means, of a known type and not shown in the figures.

In a variant of the supplying apparatus 1 not shown in the figures, the cam-lifter system comprises two connected cam elements, i.e. provided with channels adapted to receive and guide the lifter rollers, without the need to use elastic means.

The first driving means 41 comprises, for example, a first rotary electric motor which drives, through a first belt 44, a first pulley 45 mounted on one end of the cutting roller 3. In another variant of the supply apparatus 1 not shown in the figures, the first driving means 41 drives only the cutting roller 3 in rotation and further driving means is provided to rotate the pressing element 8 in coordination with the cutting roller 3. For this purpose, the first driving means and the further driving means are connected and controlled by a management and control unit of the supplying apparatus 1 or of the wrapping machine so as to rotate the cutting roller 3 and the pressing element 8 in a synchronized manner during operation, as better explained in the following description.

The unwinding means 2 comprises a couple of pre- stretching rollers 31, 32, positioned between the blocking means 4 and the film reel 55 and arranged to unwind the film 50 from the latter and elastically and/or plastically stretching or lengthening it for a fixed amount or percentage. The unwinding means 2 further comprises at least one tensing roller 36 positioned downstream of the cutting means 3, with reference to the feeding direction F of the film 50, and arranged to keep the film 50 exiting the pre-stretching rollers 31, 32 under tension, so as to facilitate the cutting of the same by the cutting means 3.

The pre-stretching rollers 31, 32 are motorized and in particular set in rotation by second driving means 42, comprising, for example, a second rotary electric motor. More precisely, the second motor 42 drives, by means of a second belt, a second pulley mounted on one end of the first pre-stretching roller 31 (fast roller) placed downstream of the second pre- stretching roller 32 (slow roller). The latter is mechanically connected to the first pre- stretching roller 31 by means of motion reduction means of a known type and not shown in the figures, so as to rotate at a lower speed in order to stretch or lengthen the film 50 for a fixed percentage (as a function of the difference of the rotation speed between the two rollers).

The pre-stretching rollers 31, 32 are abutted by respective abutting rollers 33 and 34 which ensure the proper adherence of the film 50 to the aforesaid pre-stretching rollers 31, 32. The abutting rollers are freely mounted to rotate on the respective ends of adjustment levers 35, with the opposite ends being rotatably fixed to the frame 10. The adjustment levers 35 make it possible to adjust the pressure or force exerted by the abutting rollers 33, 34 on the film 50 i.e. on the pre-stretching rollers 31, 32.

Third driving means 43 is provided for rotating the tensing roller 36 with a speed equal to or slightly greater than that of the first pre-stretching roller 31 in order to maintain the portion of film 50 between the aforesaid rollers stretched or in tension and facilitate the cutting.

In operation, the pre-stretching rollers 31, 32 and the tensing roller 36 impart a travel or unwinding speed V to the film 50 which is linked to and dependent on a wrapping speed of the film itself around the product or group of products, imparted by the wrapping unit. The third driving means 43 comprises, for example, a third rotary electric motor which drives, through a third belt 46, a third pulley 47 mounted on one end of the tensing roller 36.

A further tensing roller 37 is also provided which is adapted to abut and keep the film 50 adhering to the tensing roller 36. The further tensing roller 37 is freely mounted to rotate on the respective ends of second adjustment levers 38, with the opposite ends of the latter ones being rotatably fixed to the frame 10. The second adjustment levers 38 make it possible to adjust the pressure or force exerted by the further tensing roller 37 on the film 50 and to disengage and remove the latter from the tensing roller 36.

The supplying apparatus 1 also comprises a movable transferring arm 15 arranged for grasping an initial flap 50a of the film 50, generated by the cutting means 3 by cutting the film 50, and for transferring said initial flap 50a to the wrapping unit of the wrapping machine.

The transferring arm 15 is equipped with a first end 15a that comprises gripping means 12, arranged to grasp the initial flap 50a of the film 50, and the abutting element 11 of the blocking means 4. The transferring arm 15 is further equipped with a second end, not shown, which is rotatably fixed to the frame 10. In this way, the transferring arm 15 is movable, in particular in rotation, between a grasping position P, wherein the first end 15a is adjacent to the cutting means 3 to enable the pressing element 8 to abut the abutting element 11 in the active position A and/or to enable the gripping means 12 to grasp the initial flap 50a of film, and a transfer position (not shown), wherein the first end 15a is adjacent to the wrapping unit to enable the gripping means 12 to transfer said initial flap 50a of film to the wrapping unit.

In the illustrated embodiment, the abutting element 11 is fixed to the first end 15a of the transferring arm 15 and, in particular, the gripping means 12 includes the aforesaid abutting element 11 which is, for example, provided with a plurality of holes for air intake so as to retain the initial flap 50a of film after the cut. In more detail, the abutting element 11 has an elongated wall which is substantially flat and has openings in connection with an air intake system of the supplying apparatus 1 or of the wrapping machine.

In a variant of the supplying apparatus 1 not shown, the abutting element 11 and the gripping means 12 are distinct and the latter comprises a gripper having at least a fixed member and a movable member which is movable by a respective linear actuator, for example a pneumatic cylinder, between a position in abutment against the fixed element to grip and block the initial flap 50a of the film and a position spaced apart from aforesaid fixed element to allow the release of the initial flap 50a and/or the passage of the film 50. The operation of the film supplying apparatus 1 of the invention envisages the unwinding of the film 50 from the reel 55 performed by the pre-stretching rollers 31, 33 placed in rotation by the second driving means 42. The pre-stretching rollers 31, 33 also perform the ironing or lengthening the film 50 for a defined percentage.

The unwinding of the film 50 is also facilitated by the rotation of the tensing roller 36 set in rotation by the third driving means 43 which keeps the portion of film stretched between the tensing rollers 36, 37 and the pre-stretching rollers 31, 32, in particular at the cutting means 3 and the blocking means 4.

Once a portion 51 of film of predefined length (calculated on the basis of the shape and size of the product or group of products to be wrapped in the wrapping machine) has been delivered or unwound, the cutting means 3 is actuated in the cutting step for separating the film portion 51unwound from the reel 55, transversely cutting or shearing said film 50, and at the same time the pre-stretching rollers 31, 32 are stopped to stop the advance of the film 50 no longer required by the wrapping unit of the wrapping machine.

It should be noted that in this transitional phase of operation, the film 50 exits the supplying apparatus 1 with a high travel speed V, as it is wrapped by the wrapping unit around the product or group of products.

To perform the cut, the cutting roller 3 is placed in rotation by the first driving means 41 about the respective longitudinal axis in such a way as to abut and cut the film 50 with the blade 7. Simultaneously with the rotation of the cutting roller 3, the pressing element 8 is rotated by the motion transmission means 22 from the inactive position B, in which it is spaced from the film 50 so as not to hinder the unwinding, to the active position A, in which the abutting portion 9 blocks the film 50 against the abutting element 11, the transferring arm 15 being arranged in the gripping position P. The motion transmission means 22, and in particular the profile of the cam elements 23, is configured to ensure that the film 50 is blocked by the pressing element 8 against the abutting element 11 before the blade 7 interacts and cuts the film 50. The timing between the cam elements 23 and the lifters 24 can be suitably adjusted to precisely define the relative position between the cutting roller 3 and the pressing element 8 and, more precisely, the position of the blade 7 and the abutting portion 9 with respect to the film 50.

Before or at the same time as the beginning of the cutting phase, the pre-stretching rollers 31, 32 are stopped to block any further dispensing of film 50 i.e. of the next portion of film to wrap around another product or group of products. It should however be noted that, thanks to the blocking means 4 which intervenes before the blade 7 cuts the film 50, by virtue of the mechanical connection between the cutting roller 3 and the pressing element 8 (through the motion transmission means 22), the film 50 is blocked in an immediate, secure and effective way, therefore independently from the dynamic response of the pre-stretching rollers 31, 32, which could stop with a delay, and/or a possible slipping of the film 50 with respect to the latter. In this way, the blade 7 is able to perform a precise and clean cut on the stretchable plastics film 50 completely stopped and held stretched between the pre-stretching rollers 31, 32 and the tensing rollers 36, 37 for creating portions 51 of fixed length in a repeatable manner and with flaps lacking fraying, tears and the like.

Once the material is cut, the cutting roller 3 ends its rotation and stops. At the same time the pressing element 8 is moved from the active position A to the inactive position B wherein it is disengaged from the film 50.

The portion 51 of detached film is dragged, at the travel speed, from the wrapping unit of the wrapping machine to finish the wrapping of the product or products.

The initial flap 50a of the film (and the initial flap of the film next portion 51) created by cutting and stopping (since the pre-stretching rollers 31, 32 are stopped) is retained by the gripping means 12 positioned on the first end 15a of the transferring arm 15 still arranged in the gripping position P. The gripping means 12 includes the abutting element 11 provided with a plurality of openings for air intake.

The transferring arm 15 is then rotated from the gripping position P to the transfer position in which the first end 15a with the gripping means 12 that retains the initial flap 50a of film is adjacent to said unwinding unit to allow the transfer of aforesaid initial flap 50a to the unwinding unit.

The supplying apparatus 1 of the invention therefore makes it possible to supply, even at high travel speed V, portions of defined length of stretchable film to a wrapping unit of a wrapping machine. In fact, the blocking means 4 intervenes in a fast and effective way to block the moving film 50 for the amount of time necessary to perform the cut by means of the cutting means 3 thanks to the coordinated and in-step motion of the cutting roller 3 and the pressing element 8. In this way it is not necessary, as in the known cutting systems, for the tangential speed of the blade to be equal to the travel speed V of the film, since the blade cuts a portion of the film which is stationary, blocked between the pressing element 8 and the abutting element 11. It is therefore not necessary to impart high accelerations and decelerations to the cutting rollers, even with high travel speeds V of the film which, on the basis of tests carried out by the applicant, can thus reach values up to 12-14 m/s. In particular, the tests have shown that in order to obtain precise and clean cuts it is sufficient that the tangential speed of the blade is equal to approximately one half of the travel speed V of the film.

Moreover, thanks to the blocking means 4, the pre- stretching rollers 31, 32 and the tensing rollers 36, 37 do not have to be completely stopped in order to be able to perform precise and clean cuts. In fact, the elasticity of the stretchable plastics film makes it possible to have a film portion that is stopped (the film portion blocked and subjected to the cut) while portions of film upstream and downstream are still moved by the tensing rollers 36, 37 and by the wrapping unit and the pre-stretching rollers 31, 32 respectively, without causing any film breakage.

The movement of the cutting roller with the lowest speed and angular acceleration/deceleration values makes it possible to optimize the operation and longevity of the blade, avoiding the onset of abnormal and excessive structural/mechanical stresses. It should be noted that by blocking the film suitably kept stretched between the pre- stretching rollers 31, 32 and the tensing rollers 36, 37, the supplying apparatus 1 of the invention is capable, even at high travel speeds V of the film, of supplying in a precise and repeatable way film portions 51 of fixed length cut precisely and cleanly, without fraying or tearing at the edges.

The supplying apparatus 1 is compact and efficient because the transferring arm 15 provided with the abutting element 11 of the blocking means 4 and with the gripping means 12 are able to perform the dual function of cooperating with the pressing element 8 to block the film during the cutting and grasp and hold an initial flap 50a of the film 50, generated by the cutting means 3 by cutting the film 50, and then transfer it to the wrapping unit of the wrapping machine.

The supplying apparatus 1 is also particularly robust and reliable thanks to the simplicity of the cutting means 3, blocking means 4, driving means and motion transmission means 22 which comprises a cam-lifter system.