The invention relates to machines for wrapping a load with of stretchable plastic material film. In particular, the invention relates to a gripping apparatus arranged to grip and retain a film portion at the end of the load wrapping process.

In known wrapping machines the plastic material film, typically a cold stretchable plastic material film, is unwound from a reel supported by an unwinding apparatus and is wrapped around a load, generally arranged on a pallet, in such a manner as to form a series of braided and/or overlapped strips or coils, thanks to the combination of a movement in the vertical direction of the unwinding apparatus and the relative rotation between the latter and the load.

In wrapping machines provided with a rotating table for supporting the load, the latter is rotated around a vertical wrapping axis, while the unwinding apparatus is vertically moved with alternate motion.

In wrapping machines with horizontal ring or rotating arm, the load is fixed during the wrapping, while the unwinding apparatus is moved with respect to the load both in rotation around the vertical wrapping axis and in translation along the latter.

The unwinding apparatus supports the film reel and comprises a couple of pre-stretching rollers arranged to unwind the film from the reel and stretch or extend it and one or more return rollers arranged to divert the film toward the load. By suitably adjusting the difference between the rotation speeds of the pre-stretching rollers, it is possible to stretch the film exiting from the unwinding apparatus by a defined amount.

At the end of wrapping process, namely when the load has been wrapped with a prescribed number of braided film strips, the relative rotation between the unwinding apparatus and the load is stopped for fixing an end flap of the film to the load and thus fastening the wrapping. For performing this operation gripping apparatuses are generally used which allow to grip and retain the film at a region comprised between the unwinding apparatus and the load and welding and cutting apparatuses that allow fixing and separating an end flap of the film to the load. More precisely, a portion of film coming from the reel is pressed by a welding element against the film that is wrapped around the load. The portion of film that is welded on the wrapped film blocks the film wrapping around the load.

After welding, the film is cut in such a manner as to carry out a first end flap, which is welded and fixed to the load, and a second end flap, which is connected to the reel and retained by the gripping apparatus for allowing the wrapping of a following load. The gripping apparatus releases the film once the wrapping of the following load is started, typically after at least one wrapping round. The film end flap thus can be wrapped around the load by the film itself.

The gripping apparatus and the welding and cutting apparatus are generally placed on the rotating table or beside and adjacent to the latter or to the supporting and moving means of the load for allowing fixing the film not only to the load but also to a pallet, on which the load is placed.

The gripping apparatus typically comprises pliers provided with two mobile and opposite jaws or beaks that are able to grip and retain the film and then to release the latter when the wrapping is started. The pliers are arranged vertically. In the open position both jaws are spaced apart for releasing the film and for allowing the film to be wrapped around the load, while in the closed position the jaws are in abutment so as to grip and retain the film.

A drawback of the known gripping apparatuses consists in the pliers' size, in particular the jaws size, which must be such as to allow a correct and tight grip of the film in the closed position and a free wrapping of the film around the load in the open position. The two requirements are, however, opposed. The jaws in fact have to be long enough to allow to grip and retain a portion of film suitably long to avoid, during wrapping, that said portion may tear, with the consequent detachment of the film end flap, as a result of the tension stresses acting on the film itself. At the same time, the jaws have to be short enough in order not to limit and prevent the wrapping by interfering with the film, in particular with the wrapping of the lower portions of the film and underlying pallet.

To overcome this drawback pliers are generally interchangeable, replaceable according to the size of the load and/or the strip width of the film (typically between 125 mm and 500 mm).

This solution is however expensive and complex because it requires a set of gripping pliers having different sizes and replacement operations which require to stop the wrapping machine and thus the production.

Alternatively, in order to overcome such drawbacks there are known apparatuses that allow reducing the film width, substantially by corrugating and narrowing the end flap and the portion of film to be welded and retained. For this purpose, the welding and cutting apparatus or the unwinding apparatus comprises a gripping element (i.e. a spring) which grips and corrugates the film. However, this solution is expensive and complex.

Another drawback of the known gripping apparatuses is that, during the pliers opening in the release step, due to the relative rotation of the load with respect to the unwinding apparatus, the film may stick to, wrap to, and be caught on one of the pliers jaws, this causing a malfunction of said pliers in the subsequent step of the gripping of the film and/or an incorrect wrapping of the load, the end flap of the film being not properly wrapped around the load.

For overcoming this drawback compressed air blowing systems are known and used in wrapping machines that comprise blowing nozzles arranged around the gripping apparatus and directed towards the end flap of film for avoiding that the film sticks to and is wrapped to the pliers. These pneumatic systems are, however, expensive and complex to install and use.

An object of the invention is to improve the known gripping apparatuses associable to a wrapping machine for gripping and retaining an end flap of a stretchable plastic material film at the end of a wrapping process of a load.

Another object is to carry out a gripping apparatus, which allows correctly and tightly gripping and retaining an end flap of a film regardless of width thereof.

A further object is to provide a gripping apparatus, which does not interfere in any way with the wrapping of the load in a disengagement configuration.

Still another object is to carry out a gripping apparatus, which allows to easily and correctly release the film avoiding possible undesired wrapping.

Another further object is to carry out a simple and inexpensive gripping apparatus having a precise, effective and reliable operation.

These objects and others are achieved by an apparatus according to one or more of the following claims.

The invention can be better understood and implemented with reference to the attached drawings which illustrate some exemplifying and not limitative embodiments, wherein:

Figure 1 is a perspective view of the gripping apparatus of the invention with pliers in a gripping position;

Figure 2 is a perspective view of the gripping apparatus of the invention with pliers in a releasing position;

Figure 3 is a plan view of the gripping apparatus of Figure 1 without a covering case for better showing the pliers and the inner parts;

Figure 4 is a longitudinal section of the apparatus of Figure 2;

Figure 5 is a perspective view of the apparatus of Figure 2 without a covering case;

Figure 6 is a partial and enlarged longitudinal section of the apparatus of the invention which illustrates the pliers arranged in the gripping position and, illustrated in dotted line, in the releasing position; Figure 7 is a perspective view of the gripping apparatus of the invention associated with a wrapping machine with rotating table and with the pliers in the closed gripping position;

Figure 8 is a top plan view of the apparatus and of the wrapping machine of Figure 7. With reference to Figures 1 to 6, is illustrated the gripping apparatus 1 of the invention associated to a wrapping machine 60, suitable to wrap a load 100 with a film 50, made in stretchable plastic material, and arranged to grip an end flap 50a of the said film 50 at the end of the wrapping process of the load 100.

The gripping apparatus 1 comprises pliers 2, supporting means 5 which supports the pliers 2 and actuator means 10, 11 fixed to the supporting means 5 and arranged to move the pliers 2 between a closed gripping position A and an open releasing position B of the film 50.

The pliers 2 comprise a first lever 3 and a second lever 4 that are mutually hinged around a first axis XI and provided respectively with a first gripping jaw 31 and a second gripping jaw 41 that are arranged to tighten the film 50 in the gripping position A. In particular, the first lever 3 and the second lever 4 are mutually rotatably coupled around the first axis XI at respectively a first central portion 33 and a second central portion 43.

In the gripping position A the pliers 2 are closed, the jaws 31, 41 being in abutment for tightening and retaining the film 50. In the releasing position B, the pliers 2 are opened, the jaws 31, 41 being rotated and spaced apart for not releasing the film and not interacting with the latter, as better explained in the following description.

The first lever 3 comprises a first connecting end 32 opposed to the first jaw 31 and rotatably fixed to the supporting means 5, while the second lever 4 comprises a second operating end 42 opposite to second jaw 41 and rotatably connected to the actuator means 10, 11. The second operating end 42 is linearly moved by the actuator means 10, 11 along a first displacement direction C in such a manner that the jaws 31, 41 of the levers 3, 4 of the pliers 2 are mobile with a composed motion around the first axis XI, along the first displacement direction C and along a second displacement direction D that is transversal, in particular substantially orthogonal, to the first displacement direction C.

The first connecting end 32 of the first lever 3 is fixed to the supporting means 5 and rotatable around a second axis X2, which is nearly parallel to the first axis XI .

The second connecting end 42 of the second lever 4 is coupled to the actuator means 10 and rotatable about a third axis X3, which is almost parallel to the first axis XI . The apparatus 1 also comprises guiding means 6 that is associated with the second connecting end 42 of the second lever 4 and arranged for linearly guiding the second connecting end 42 along the first displacement direction C. More precisely, the guiding means comprises a roller 6, or wheel, rotatably fixed, around the third axis X3, to the second connecting end 42 and mobile on an abutting wall 15 of the supporting means 5 so as to guide and support the second lever 4, both when moving between the releasing position B and the gripping position A and vice versa and in the gripping position A of the pliers 2. Alternatively, the guiding means 6 can comprise a sliding block fixed to the second connecting end 42 and slidably engaged with a linear guide that is fixed to the abutting wall 15 of the supporting means 5.

The supporting means 5 comprise a support frame 12 to which the pliers 2 and the actuator means 10, 11 are fixed and a box-shaped covering case 13, for example having the shape of an elongated parallelepiped, that is fixed in a removable manner to the support frame 12 so as to enclose the latter and define an inner cavity 25 that is arranged to house the actuator means 10, 11 and the pliers 2, in the releasing position B. The covering case 13 is provided with an opening 14, which allows the levers 3, 4 coming out in the gripping position A.

In the embodiment shown in the figures, the actuator means comprises a linear actuator 10 arranged to move the second lever 3 and the first lever 2 between the releasing position B and the gripping position A. The linear actuator 10 is, for example, a pneumatic or hydraulic cylinder, or may comprise a linear electric motor or screw-nut system actuated by a rotating electric motor or other equivalents moving mechanisms. In the illustrated embodiment, the linear actuator 10 is a single acting cylinder and the actuator means also comprises elastic means 11 fixed to the supporting means 5 and to the second connecting end 42 of the second lever 4 for moving the latter and the first lever 3 between the gripping position A and the releasing position B. The elastic means 11 comprises, for example, a helical spring acting in traction, fixed at its respective ends to the second connecting end 42 of the second lever 4 and to a hooking element 19 positioned in the inner cavity 25. As particularly illustrated in Figures 3 and 5, the first lever 3 is hinged at the first connecting end 32 to a first bracket 16 of the supporting means 5 that is positioned at the first end portion 5a of the latter. Similarly, an end of the linear actuator 10 is hinged to a second bracket 17 of the supporting means 5 that is positioned at a second end portion 5b of the supporting means 5 that is opposite to the first end portion 5a. The opening 14 for allowing the pliers 2 coming out extends longitudinally parallel to the first direction of movement C, from the first end portion 5a of the supporting means 5 and towards the second end portion 5b. The length of the opening 14 is such to allow the rotating and translating movement of the levers 3, 4 from the releasing position B to the gripping position A and vice versa.

The apparatus 1 also comprises diverting means 18 fixed to one of the jaws 31 of the pliers

2 and to the supporting means 5 so as to prevent the film 50, in particular to the end portion 50a thereof, to stick to and/or wrap to the pliers 2 when the levers 3, 4 are moved from the gripping position A to the releasing position B for releasing the said end flap 50a, in an initial step of a wrapping process of a load 100.

The diverting means comprises a flexible elongated element 18, such as a tape or belt made of plastic or metallic material, provided with a first end portion 18a fixed to the first jaw 31 of the first lever 3 and a second end portion 18b fixed elastically to the supporting means 5. In particular, the second end portion 18a is fixed through further elastic means 21 to hooking means positioned in the inner cavity 25. The further elastic means 21 keeps taut and under tension the flexible element 18 which, in the gripping position of the pliers A, comes out from the opening 14 of the, sliding on a guiding portion 24 of said supporting means 5 that is carried out at the opening 14. The further elastic means comprises, for example, a couple of helical springs 21 acting in traction, fixed to the ends of second end portion 18b of the flexible elongate element 18 and to respective hooking means of supporting means 5, that is positioned at opposite side with respect to the levers 3, 4.

The flexible elongated element 18 in the gripping position A is substantially superimposed on the opening 14 thus preventing the end flap 50a to stick to and wrap around the levers 2,

3 and/or engage the opening 14.

As illustrated in Figures 7 and 8, the gripping apparatus 1 of the invention may be associated with a wrapping machine 60 arranged for wrapping a load 100 with the film 50. In the embodiment shown by way of non-limiting example, the wrapping machine 60 is a wrapping machine comprising a table or platform 61 that is rotatable around a vertical axis Z and arranged to support the load 100 to be wrapped. The machine 60 includes a column 62 that is positioned at the side of the rotating table 61 and slidably supports an unwinding apparatus 63 comprising a reel 51 from which the film 50 is unwound, and pre-stretching and return rollers which stretch or extend the film 50 before the wrapping and then to head the film outside towards the load 100. The machine 60 is provided with a welding and cutting apparatus 64 of the film 50 that is arranged to fix the film 50 to the load 100 at the wrapping end and then cut the film so as to carry out two end flaps 50a, 50b, a first end flap 50a that is retained by the gripping apparatus 1 and a second end flap 50b that is fixed to the load 100.

For this wrapping machine type, the gripping apparatus 1 of the invention is fixed to the rotating table 61 at a peripheral edge thereof, so as to be adjacent to the load 100 and to a pallet 110 on which the load 100 is positioned.

The gripping apparatus 1 can be also associated to a wrapping machine with rotating arm or to a wrapping machine with horizontal rotating ring. In this case, the gripping apparatus 1 is static, typically connected to supporting and moving means (roller conveyor) which supports and moves the load inside and outside the machine.

The operation of the gripping apparatus 1 of the invention is now described in relation to the operation of the wrapping machine 60.

In a terminal step of the wrapping process of the load 100, the cutting and welding apparatus 64 is approached to the load itself in order to fix to the load the film 50 and then to cut the latter so as to obtain two end flaps 50a, 50b. Before the cutting, the gripping apparatus 2 is actuated and the pliers 2 are moved by the actuator means 10, 11 with a closing movement from the releasing position B to the gripping position A. In the releasing position B the pliers 2 are substantially open and fully enclosed in the inner cavity 25 of the supporting means 5 so as not to interfere with the previous wrapping of the film 50 around the load 100, the jaws 31, 41 being rotated and spaced apart each other.

In the gripping position A the pliers 2 come out from the inner cavity 25 of the supporting means 5 through the opening 14 and are substantially closed so as to tighten and retain the film 50. The jaws 31, 41 abut each other and tighten the film 50, the levers 3, 4 are arranged in a substantially vertical position.

It should be noted that thanks to the articulated connection of the levers 3, 4 that are connected to each other and to the supporting means 5 and the actuator means 10, during the closing movement the levers 3, 4, and in particular the respective jaws 31, 41, move with a composed motion around the first axis XI, along the first displacement direction C and along a second displacement direction D that is orthogonal to the first displacement direction C. More precisely, the levers 3, 4 rotate relatively to each other around the first axis XI, which moves along the first displacement direction C and along the second displacement direction D that are orthogonal to each other. In this manner, the jaws 3, 4 are rotated by an angle so as to tighten the film 50 and are also moved upwards along the second displacement direction D by a distance LI so as to grip, drag and fold a greater amount of film 50. More precisely, unlike the known pliers, the gripping apparatus 1 of the invention allows to grip, by corrugating or folding, a portion of film having a first length L2 much greater (more than twice) than a second length Lb of the jaws 31, 41.

Thanks to the gripping apparatus 1 of the invention it is therefore possible to grip and retain in a tight and safe manner films 50 having a bandwidth ranging from minimum values to maximum values, even with the apparatus 1 having particularly reduced and compact size and overall dimensions, particularly in height.

It should be noted, in fact, that in the releasing position B, the pliers 2 are opened and completely enclosed inside the inner cavity 25 of the supporting means 5, having very small overall dimensions, which do not hinder or prevent the wrapping of a lower portion of the load 100 and/or the pallet 110.

Once the film 50 is gripped by the pliers 2 of the gripping apparatus 1, the cutting and welding apparatus 64 cuts the film 50 thus creating the two end flaps, one of which (the first end flap 50a) is tightened and retained by the pliers 2.

The load 100 that is correctly wrapped can be thus removed from the machine 60 in order to make way for a subsequent load 100 to be wrapped.

In the initial steps of the subsequent wrapping process, the load 100 is rotated so as to be wrapped with the film 50 and the pliers 2 in the gripping position A retains the first end flap 50a. When the load is partially wrapped with one or more bands of film 50, the pliers 2 can be moved in the releasing position B so as to release said first end flap 50a which can be completely wrapped by the film 50 on the load 100.

During the opening movement of the levers 3, 4 from the gripping position A to the releasing position B, the diverting means 18, comprising the flexible element that is connected to the first jaw 31 of the first lever 3, prevents that the first end flap 50a, once released may stick to said first lever 3 and get caught on, or wrap around, said first lever 3, thus remaining detached from wrapping of the load 100, or stopping the operation of the pliers 2 by entering into the inner cavity 25 through the opening 14.

It should be noted that the flexible element 18 is substantially superimposed on the opening 14 and kept in tension by further flexible means 21 so as to be a sort of barrier that prevents the film 50, in particular the first end flap 50a, to engage the pliers 2 and/or the opening 14. Thanks to the flexible element 18, the gripping apparatus 1 of the invention therefore allows to release easily and correctly the film 50 thus avoiding possible undesired wrappings thereof around the pliers 2.