Accumulative hodding apparatus and relative hodding method

Abstract

A wrapping method and related hooding apparatus including a support frame are described, on which it is arranged a system for forming a hood (C) of tubular plastic film, and a application frame designed to transfer said hood (C) along a translation axis along a load to be wrapped residing in a wrapping station, said application frame being provided with a plurality of accumulative grippers (P1-P(4)able to be mutually spread apart, each of said accumulative grippers (P1-P4) having at least one main prong (3) provided with a motorised roller (8) capable of pushing said hood film (C) to accumulate on said main prong (3) and of accompanying said hood film (C) to unroll itself from said main prong (3), wherein said motorised roller (8) is set in rotation by means of a belt drive (7) closed in a loop, which runs in the direction of said main prong (3), passes over idler rollers (6) and around a drive pinion (5a) of a relative motor (5) and wherein said motorised roller (8) has a main axis of rotation (a-a) and is rotationally coupled to at least a pair of auxiliary rollers (13), opposed on both sides of said motorised roller (8), having their respective axes of rotation (b-b, c-c) in the same plane of said main axis of rotation (a-a) but converging with each other by an angle (δ).

Description

FIELD OF THE INVENTION

[0001] The present invention relates to the field of machines for hooding articles through tubular film wrapping. In particular, the present invention relates to accumulative hooding machine and a method of operation thereof.STATE OF PRIOR ART

[0002] Many systems and types of machines are known in the wrapping field of palletised loads. Amongst these, the present discussion will focus on hooding machines, i.e. machines suitable for creating a tubular hood - of a length proportional to the height or length of the load to be wrapped - and then fitting this hood onto the load.

[0003] To this end, modern hooding machines, especially automatic ones, are equipped with sensors to accurately measure the height of a load on a pallet and prepare a custom-made thermoplastic tubular film. The tubular film is cut and sealed, e.g. heat-sealed, at one end and then prepared through automatic systems to be transported on the load to be applied to the pallet.

[0004] In the context of this application, we will explicitly describe a machine that applies a tubular hood in a vertical direction, but in principle the same configuration could be used in different directions, e.g. along a horizontal axis.

[0005] The tubular film therefore has one end closed, and the other end open, so that it can be applied onto the load.

[0006] The hood is typically formed sideways, on one side of the load to be packed, and the sealing of the tubular film can take place at the upper or lower end.

[0007] The hood can be applied to the load in straight way - i.e. with the outer side of the tubular film remaining on the outside even when the hood is fitted on the load - or in reverse way - i.e. reversed with the outer side of the tubular film and the sealing line on the inside of the package once it is applied on the load.

[0008] There are also two types of application. On the one hand, the hood can be put over the load by dragging it from the opening edge using transport grippers, after inflating it with a dynamic movement or by stretching it appropriately with motorised spreader systems. On the other hand, the tubular film is accumulated on four pegs arranged at the vertices of a four-sided frame, curling it over the extension of the pegs, and then applied by rolling it out as the peg frame is moved along the load.

[0009] If a heat-shrinkable film is used, the last step of wrapping involves a shrinking of the film, making it adhere around the load, achieved by appropriate heating. In contrast, when a stretchable film is used, the step of adapting the hood to the load is preceded by a temporary stretching event of the hood itself.

[0010] Generally speaking, however, all accumulative hooding machines have a significant problem when unrolling the hood over the load, as the peripheral edge of the opening edge is only held and guided well at the pegs and therefore tends to be affected by friction against the load and thus form loops or bending that do not allow for regular wrapping.

[0011] To overcome these problems, the same Applicant disclosed in EP 1 510 460 an accumulative hooding machine with telescopic rods. In particular, as depicted in the two side elevation views in Figs. 1 and 2, the motorised accumulation pegs depend downwards from an upper spreading frame and are connected to each other by telescopic rods arranged along the four perimeter sides. In this manner, the entire perimeter of the opening edge, facing downwards, rests both on the lower fittings of the pegs and on the cylindrical surface of the telescopic rods, so as to avoid the formation of loops during unrolling.

[0012] The solution disclosed in EP 1 510 460 provides that the hood is applied in an reversed manner. The hood is formed laterally to the load, with the opening edge facing upwards and sealed at the bottom (Fig. 1A); then the application frame is moved over the load and lowered downwards to unroll the reversed hood over the load.

[0013] Although the reverse application of the hood on the load has the advantage of hiding the sealing line inside the packaging, it has the peculiarity of inverting the inside and outside of the tubular film: what was initially the outside of the hood, becomes the inside and vice versa. Hood reversed therefore has limitations in those cases where the plastic film has prints (such as company logos or other load information) that are inevitably inverted. A first logical solution to inversion is to supply films with inverted printing, but this involves higher costs for the procurement of inverted printed films.

[0014] A different conceptual approach is to rotate the accumulative frame completely by 90° (around a horizontal axis) before the application stage, or to accumulate the hood from above on accumulative pegs facing upwards. An example is DE 39 08 957.

[0015] Both of these latter solutions involve construction complications but, above all, they also require load lifting mechanisms. In fact, when the accumulative pegs are projecting upwards, the frame and motorisation part is placed on the lower side and is so bulky that it prevents the hood opening edge from being transferred to the load bearing surface. It is therefore necessary to provide a load lifting system, which introduces the load inside the hood entirely lowered at least to a height equal to the height of the peg frame.

[0016] An initial technical solution to the problem just outlined has been disclosed in EP 1 762 493 and EP 1 990 277, which involve the use of motorised accumulative grippers rotatable on a horizontal axis. In this case, the accumulative grippers are used facing upwards at the phase when the hood is put on the pegs and then begins to be applied to the load; but, then, the grippers are rotated to bring the opening edge of the hood to the lowest point of the application frame, eliminating the drawback seen above.

[0017] This solution appears advantageous in theory, but operationally it has not been successful because it has serious drawbacks that make it unusable. First of all, the specific configuration proposed does not allow an effective unrolling of the hood from the accumulative gripper. But more importantly, the presence of a rotational movement of the motorised gripper does not allow for supporting means of the hood opening edge, such as telescopic rods or flexible ropes as described above.

[0018] In other words, the problem already discussed above, related to the formation of flaws / pockets / wrinkles in the hood during unrolling on the load, is appearing again.

[0019] Particular configurations of the accumulative peg have also been proposed in the prior art, with an angular support of the tubular film equipped with sliding wheels that facilitate the sliding of the film. Examples are shown in EP 1 275 581, EP 1 266 828 and EP 1 818 261. However, the Applicant has found that the application of these solutions is not sufficient to solve the issues connected with the tubular film.

[0020] In the field of packaging, other systems that facilitate the transfer of tubular film using different transfer means are already known. An apparatus for applying heat-shrinkable tubular labels, equipped with a transfer belt, is illustrated in US 4806187.PROBLEM AND SOLUTION

[0021] The problem at the basis of the invention is therefore to supply a hooding machine, comprising an accumulative mechanism as proposed in EP 1 762 493 or EP 1 990 277, that overcomes the mentioned drawbacks, in particular that enables efficient hood unrolling and hood application on the load.

[0022] This is achieved through the features mentioned in essential terms in the independent claims appended hereto. The dependent claims describe preferential features of the invention.BRIEF DESCRIPTION OF THE DESIGNS

[0023] Further features and advantages of the invention will, however, be best illustrated by the following detailed description of a preferred embodiment, given purely as an example and not as a limitation, and illustrated in the accompanying drawings, wherein: fig. 1A is a side elevation view of a prior art hooding equipment as depicted in EP 1 510 460; fig. 1B is a side elevation view of another prior art hooding equipment as depicted in EP 1 990 277; Fig. 2 is a longitudinal sectional view of an accumulative gripper according to the present invention; Fig. 3 is a cross-sectional view according to line III-III of Fig. 2 in an open condition of the gripper; and Figs. 4A-4F are diagrammatic views illustrating the operation of a hooding machine according to an embodiment of the present invention. DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

[0024] In fig. 1B it is illustrated an exemplary hooding machine of prior art (as disclosed in EP 1 990 277), comprising a frame - arranged astride a roller conveyor on which a load to be wrapped is placed - above which it is arranged a mechanism for forming a plastic film hood C and a application frame, vertically movable, on which are installed four accumulative grippers P 1 -P 4 facing upwards and movable each other to perform a spreading movement.

[0025] The operation of this general part of the machine will not be further described here because it is known to a skilled in the field and is in any case described in EP 1 762 493 and EP 1 990 277, which are taken here as a reference.

[0026] The general configuration of the machine frame in relation to the load packing station, as well as the way the hood is formed can also be different, for example with the grippers P 1 -P 4 facing downwards as shown in EP 1 510 460.

[0027] A motorised accumulative gripper 1 is shown in cross-section in Fig. 2.

[0028] The accumulative gripper 1 has a generic fork arrangement, provided with appropriate bearing surfaces 2 on which the plastic film of the tubular hood C is intended to be accumulated and then released. The fork has a portion of main prong 3, which supports at its end a motorised roller 8, and a portion of secondary prong 4, which supports at its end an idler abutting roller 11, mounted on a tilting bracket 9.

[0029] The tilting bracket 9 is preferably driven by an actuator 10 which, by means of a rotational movement, can alternately bring the idler roller 11 into contact with or away from the motorised roller 8.

[0030] According to a peculiar feature, the motorised roller is set into rotation by means of a closed-loop drive belt 7, which runs in the direction of the main prong 3 and is deflected by two deflection rollers 6 towards a drive pinion 5a of a related motor 5.

[0031] One of the two deflection rollers 6 is mounted on a drive rail by means of adjusting means, so that it exerts a belt tensioning function on drive belt 7.

[0032] The motor 5 is attached to a reference plate 12 to which the two prongs 3 and 4 of the fork are also attached.

[0033] The motorised roller 8 is rotationally mounted on a rotation axis a-a, which is arranged substantially horizontally at least during the accumulation phase of the tubular film and is parallel to the rotation axis of the idler roller 11.

[0034] According to the exemplary variant disclosed, the gripper 1 is also equipped with a tilt motor M, mounted on the opposite side of the prongs 3 and 4 to the drive motor 5, which is intended to control the rotation of the entire gripper by approximately 180° with respect to a horizontal axis, which rotation serves to bring the prongs 3 and 4 from an upward to a downward direction, and vice versa. A possible mode of operation and interaction of the motor M with respect to the frame on which the grippers P 1 -P 4 are installed will not be further discussed herein, because it is known from the prior art documents EP 1 762 493 and EP 1 990 277 cited above and is not a specific subject matter of the present invention.

[0035] According to the invention, moreover, the motorised roller 8 is rotationally coupled with at least two auxiliary rollers 13, opposed to each other on both sides of the motorised roller, having respective rotation axes b-b and c-c in the same plane of the rotation axis a-a of the motorised roller 8, but with angles converging with each other by an angle δ. The vertex of the angle δ faces the outside of the gripper, i.e. the outside of the tubular hood C.

[0036] The angle δ is preferably about 90° (corresponding to an edge of a quadrilateral geometric figure), but it cannot be excluded that it may be wider or narrower by a few degrees depending on the specific material or configuration of the tubular film.

[0037] According to one variant, the auxiliary rollers 13 are mounted in such a way that the convergence angle δ can be adjusted depending on the conditions of use, e.g. a smaller angle in the film accumulation phase and a larger angle in the film unrolling phase.

[0038] Each of said auxiliary rollers 13 is integrally connected in rotation to the motorised accumulative roller 8, for example by means of bevel gears 14 within a support case 15 (within which rolling bearings are mounted) or by means of universal joints or other similar means.

[0039] The two auxiliary rollers 13 shown in fig. 3 may also be longer in length or may be more than two in number adjacent to each other on the same axis of rotation.

[0040] According to a preferred feature of the invention, moreover, the rotation speed of the motor 5 and, consequently, that of the main motorised roller 8 and auxiliary rollers 13, is controlled as a function of the downward speed of the gripper 1.

[0041] In fact, once the tubular film has been accumulated on the four P 1 -P 4 grippers at the four vertices of the application frame, the latter is lowered onto the load, progressively applying the hood which unrolls from the grippers themselves, at a certain rate of descent. The descent speed may vary during the application of the hood, for example with a slower start and progressively faster run, because in the first phase there is a greater criticality both for the greater tension of the accumulated film, which tends to create loops, and for the stability of the load.

[0042] According to this preferred aspect of the invention, the rotation of the main motorised roller 8 and the auxiliary rollers 13 is controlled according to the (downward) translation speed of the grippers relative to the load.

[0043] This allows the rotation speed of the motorised roller 8 to be matched to the speed at which the hood is unrolled from the gripper 1, minimising friction or strain between the film and rollers 8, 13 which would otherwise create unwanted loops at the hood opening edge.

[0044] According to this aspect, the peripheral speed of roller 8 does not necessarily have to be the same as the translation speeds of the gripper, but the speed of roller is expected to be controlled as a function of the translation speed. For example, the peripheral speed of motorised roller 8 is slightly different, with a variable deviation, from the translation speed of the gripper.

[0045] With this method of control, it has been noted that the formation of loops is completely avoided, even in the complete absence of the supporting means of film, i.e. telescopic rods or flexible ropes of prior art.

[0046] This effect translates into a significant advantage in machine construction, which is particularly favourable in the case of rotatable grippers on a horizontal axis - as in the exemplary case illustrated - but also in the case of fixed motorised grippers.

[0047] In the operation of the gripper 1, the free leading edge of the tubular film C is inserted between the two prongs 3 and 4 and brought to rest against the main prong 3. Then the gripper 1 is closed by bringing the idler roller 11 to rest against the motorised roller 8, with a pressure determined by the actuator 10, pinching the film of the tubular hood C in the middle. At this point, the motor 5 is operated causing the movement of the belt 7 and the roller 8, which rotates counterclockwise (with respect to the plane of fig. 2) together with the auxiliary rollers 13: the film is then dragged inside the fork, accumulating on the main prong 3 between the roller 8 and the bottom portion of the fork.

[0048] In the unrolling phase, when the application frame moves down along the load to be wrapped, the film is released from gripper 1 in the opposite process to that of accumulation and with a rotation speed of rollers 8 and 13 controlled according to the translation speed of the gripper and the application frame.

[0049] Figs. 4A-4F diagrammatically show the accumulation and unrolling phases for an exemplary case, in which the motorised accumulative pegs are facing upwards and the hood is applied straight on, as in the IS44 machine produced by the same Applicant, but the pegs are in the shape of pivoting grippers on a horizontal axis.

[0050] Fig. 4A shows the phase of picking up the plastic film hood, with the grippers facing upwards (only two out of four are shown). Fig. 4B shows the phase of accumulating the hood on the grippers and Fig. 4C shows a phase of the grippers moving away from each other, with the hood being spread apart and the plastic film stretched out. In Figs. 4D and 4E the grippers perform a 180° pivoting rotation and bring the motorised rollers to the bottom. After the complete rotation, without the hood actually being reversed over, the application frame begins to translate, moving downward onto the load. In fig. 4F, the application frame has reached the lower end and the motorised rollers are coinciding with the lower base of the load.

[0051] As is clear from the above description, the hooding apparatus according to the invention perfectly fulfils the purposes set out in the introduction.

[0052] In particular, the presence of the drive belt 7 allows the rollers 8, 13 to be driven without other, bulkier transmission gears, which allows the diameter of the roller 8 to be kept very small. The working surface and the peripheral rotation speed are therefore suitable to drive the plastic film in a more regular manner, without local deformations that would cause irregularities upon unrolling.

[0053] In addition, the presence of the auxiliary rollers 13 and the speed control of all rollers 8 and 13 in proportion to the translation speed of the grippers and the application frame, results in a very regular unrolling of the tubular film, which makes it unnecessary to use supporting rods or ropes for the opening edge of the tubular film.

[0054] It is understood, however, that the invention is not to be considered limited to the particular arrangements illustrated above, which are only exemplary embodiments of it, but that several variants are possible, all within the reach of a person skilled in the art, without, however, going beyond the scope of protection of the invention itself, as defined by the following claims.

Examples

Embodiment Construction

[0024]In fig. 1B it is illustrated an exemplary hooding machine of prior art (as disclosed in EP 1 990 277), comprising a frame - arranged astride a roller conveyor on which a load to be wrapped is placed - above which it is arranged a mechanism for forming a plastic film hood C and a application frame, vertically movable, on which are installed four accumulative grippers P 1 -P 4 facing upwards and movable each other to perform a spreading movement.

[0025]The operation of this general part of the machine will not be further described here because it is known to a skilled in the field and is in any case described in EP 1 762 493 and EP 1 990 277, which are taken here as a reference.

[0026]The general configuration of the machine frame in relation to the load packing station, as well as the way the hood is formed can also be different, for example with the grippers P 1 -P 4 facing downwards as shown in EP 1 510 460.

[0027]A motorised accumulative gripper 1 is shown in cross-section in...

FIELD OF THE INVENTION

[0001] The present invention relates to the field of machines for hooding articles through tubular film wrapping. In particular, the present invention relates to accumulative hooding machine and a method of operation thereof.STATE OF PRIOR ART

[0002] Many systems and types of machines are known in the wrapping field of palletised loads. Amongst these, the present discussion will focus on hooding machines, i.e. machines suitable for creating a tubular hood - of a length proportional to the height or length of the load to be wrapped - and then fitting this hood onto the load.

[0003] To this end, modern hooding machines, especially automatic ones, are equipped with sensors to accurately measure the height of a load on a pallet and prepare a custom-made thermoplastic tubular film. The tubular film is cut and sealed, e.g. heat-sealed, at one end and then prepared through automatic systems to be transported on the load to be applied to the pallet.

[0004] In the context of this application, we will explicitly describe a machine that applies a tubular hood in a vertical direction, but in principle the same configuration could be used in different directions, e.g. along a horizontal axis.

[0005] The tubular film therefore has one end closed, and the other end open, so that it can be applied onto the load.

[0006] The hood is typically formed sideways, on one side of the load to be packed, and the sealing of the tubular film can take place at the upper or lower end.

[0007] The hood can be applied to the load in straight way - i.e. with the outer side of the tubular film remaining on the outside even when the hood is fitted on the load - or in reverse way - i.e. reversed with the outer side of the tubular film and the sealing line on the inside of the package once it is applied on the load.

[0008] There are also two types of application. On the one hand, the hood can be put over the load by dragging it from the opening edge using transport grippers, after inflating it with a dynamic movement or by stretching it appropriately with motorised spreader systems. On the other hand, the tubular film is accumulated on four pegs arranged at the vertices of a four-sided frame, curling it over the extension of the pegs, and then applied by rolling it out as the peg frame is moved along the load.

[0009] If a heat-shrinkable film is used, the last step of wrapping involves a shrinking of the film, making it adhere around the load, achieved by appropriate heating. In contrast, when a stretchable film is used, the step of adapting the hood to the load is preceded by a temporary stretching event of the hood itself.

[0010] Generally speaking, however, all accumulative hooding machines have a significant problem when unrolling the hood over the load, as the peripheral edge of the opening edge is only held and guided well at the pegs and therefore tends to be affected by friction against the load and thus form loops or bending that do not allow for regular wrapping.

[0011] To overcome these problems, the same Applicant disclosed in EP 1 510 460 an accumulative hooding machine with telescopic rods. In particular, as depicted in the two side elevation views in Figs. 1 and 2, the motorised accumulation pegs depend downwards from an upper spreading frame and are connected to each other by telescopic rods arranged along the four perimeter sides. In this manner, the entire perimeter of the opening edge, facing downwards, rests both on the lower fittings of the pegs and on the cylindrical surface of the telescopic rods, so as to avoid the formation of loops during unrolling.

[0012] The solution disclosed in EP 1 510 460 provides that the hood is applied in an reversed manner. The hood is formed laterally to the load, with the opening edge facing upwards and sealed at the bottom (Fig. 1A); then the application frame is moved over the load and lowered downwards to unroll the reversed hood over the load.

[0013] Although the reverse application of the hood on the load has the advantage of hiding the sealing line inside the packaging, it has the peculiarity of inverting the inside and outside of the tubular film: what was initially the outside of the hood, becomes the inside and vice versa. Hood reversed therefore has limitations in those cases where the plastic film has prints (such as company logos or other load information) that are inevitably inverted. A first logical solution to inversion is to supply films with inverted printing, but this involves higher costs for the procurement of inverted printed films.

[0014] A different conceptual approach is to rotate the accumulative frame completely by 90° (around a horizontal axis) before the application stage, or to accumulate the hood from above on accumulative pegs facing upwards. An example is DE 39 08 957.

[0015] Both of these latter solutions involve construction complications but, above all, they also require load lifting mechanisms. In fact, when the accumulative pegs are projecting upwards, the frame and motorisation part is placed on the lower side and is so bulky that it prevents the hood opening edge from being transferred to the load bearing surface. It is therefore necessary to provide a load lifting system, which introduces the load inside the hood entirely lowered at least to a height equal to the height of the peg frame.

[0016] An initial technical solution to the problem just outlined has been disclosed in EP 1 762 493 and EP 1 990 277, which involve the use of motorised accumulative grippers rotatable on a horizontal axis. In this case, the accumulative grippers are used facing upwards at the phase when the hood is put on the pegs and then begins to be applied to the load; but, then, the grippers are rotated to bring the opening edge of the hood to the lowest point of the application frame, eliminating the drawback seen above.

[0017] This solution appears advantageous in theory, but operationally it has not been successful because it has serious drawbacks that make it unusable. First of all, the specific configuration proposed does not allow an effective unrolling of the hood from the accumulative gripper. But more importantly, the presence of a rotational movement of the motorised gripper does not allow for supporting means of the hood opening edge, such as telescopic rods or flexible ropes as described above.

[0018] In other words, the problem already discussed above, related to the formation of flaws / pockets / wrinkles in the hood during unrolling on the load, is appearing again.

[0019] Particular configurations of the accumulative peg have also been proposed in the prior art, with an angular support of the tubular film equipped with sliding wheels that facilitate the sliding of the film. Examples are shown in EP 1 275 581, EP 1 266 828 and EP 1 818 261. However, the Applicant has found that the application of these solutions is not sufficient to solve the issues connected with the tubular film.

[0020] In the field of packaging, other systems that facilitate the transfer of tubular film using different transfer means are already known. An apparatus for applying heat-shrinkable tubular labels, equipped with a transfer belt, is illustrated in US 4806187.PROBLEM AND SOLUTION

[0021] The problem at the basis of the invention is therefore to supply a hooding machine, comprising an accumulative mechanism as proposed in EP 1 762 493 or EP 1 990 277, that overcomes the mentioned drawbacks, in particular that enables efficient hood unrolling and hood application on the load.

[0022] This is achieved through the features mentioned in essential terms in the independent claims appended hereto. The dependent claims describe preferential features of the invention.BRIEF DESCRIPTION OF THE DESIGNS

[0023] Further features and advantages of the invention will, however, be best illustrated by the following detailed description of a preferred embodiment, given purely as an example and not as a limitation, and illustrated in the accompanying drawings, wherein: fig. 1A is a side elevation view of a prior art hooding equipment as depicted in EP 1 510 460; fig. 1B is a side elevation view of another prior art hooding equipment as depicted in EP 1 990 277; Fig. 2 is a longitudinal sectional view of an accumulative gripper according to the present invention; Fig. 3 is a cross-sectional view according to line III-III of Fig. 2 in an open condition of the gripper; and Figs. 4A-4F are diagrammatic views illustrating the operation of a hooding machine according to an embodiment of the present invention. DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

[0024] In fig. 1B it is illustrated an exemplary hooding machine of prior art (as disclosed in EP 1 990 277), comprising a frame - arranged astride a roller conveyor on which a load to be wrapped is placed - above which it is arranged a mechanism for forming a plastic film hood C and a application frame, vertically movable, on which are installed four accumulative grippers P 1 -P 4 facing upwards and movable each other to perform a spreading movement.

[0025] The operation of this general part of the machine will not be further described here because it is known to a skilled in the field and is in any case described in EP 1 762 493 and EP 1 990 277, which are taken here as a reference.

[0026] The general configuration of the machine frame in relation to the load packing station, as well as the way the hood is formed can also be different, for example with the grippers P 1 -P 4 facing downwards as shown in EP 1 510 460.

[0027] A motorised accumulative gripper 1 is shown in cross-section in Fig. 2.

[0028] The accumulative gripper 1 has a generic fork arrangement, provided with appropriate bearing surfaces 2 on which the plastic film of the tubular hood C is intended to be accumulated and then released. The fork has a portion of main prong 3, which supports at its end a motorised roller 8, and a portion of secondary prong 4, which supports at its end an idler abutting roller 11, mounted on a tilting bracket 9.

[0029] The tilting bracket 9 is preferably driven by an actuator 10 which, by means of a rotational movement, can alternately bring the idler roller 11 into contact with or away from the motorised roller 8.

[0030] According to a peculiar feature, the motorised roller is set into rotation by means of a closed-loop drive belt 7, which runs in the direction of the main prong 3 and is deflected by two deflection rollers 6 towards a drive pinion 5a of a related motor 5.

[0031] One of the two deflection rollers 6 is mounted on a drive rail by means of adjusting means, so that it exerts a belt tensioning function on drive belt 7.

[0032] The motor 5 is attached to a reference plate 12 to which the two prongs 3 and 4 of the fork are also attached.

[0033] The motorised roller 8 is rotationally mounted on a rotation axis a-a, which is arranged substantially horizontally at least during the accumulation phase of the tubular film and is parallel to the rotation axis of the idler roller 11.

[0034] According to the exemplary variant disclosed, the gripper 1 is also equipped with a tilt motor M, mounted on the opposite side of the prongs 3 and 4 to the drive motor 5, which is intended to control the rotation of the entire gripper by approximately 180° with respect to a horizontal axis, which rotation serves to bring the prongs 3 and 4 from an upward to a downward direction, and vice versa. A possible mode of operation and interaction of the motor M with respect to the frame on which the grippers P 1 -P 4 are installed will not be further discussed herein, because it is known from the prior art documents EP 1 762 493 and EP 1 990 277 cited above and is not a specific subject matter of the present invention.

[0035] According to the invention, moreover, the motorised roller 8 is rotationally coupled with at least two auxiliary rollers 13, opposed to each other on both sides of the motorised roller, having respective rotation axes b-b and c-c in the same plane of the rotation axis a-a of the motorised roller 8, but with angles converging with each other by an angle δ. The vertex of the angle δ faces the outside of the gripper, i.e. the outside of the tubular hood C.

[0036] The angle δ is preferably about 90° (corresponding to an edge of a quadrilateral geometric figure), but it cannot be excluded that it may be wider or narrower by a few degrees depending on the specific material or configuration of the tubular film.

[0037] According to one variant, the auxiliary rollers 13 are mounted in such a way that the convergence angle δ can be adjusted depending on the conditions of use, e.g. a smaller angle in the film accumulation phase and a larger angle in the film unrolling phase.

[0038] Each of said auxiliary rollers 13 is integrally connected in rotation to the motorised accumulative roller 8, for example by means of bevel gears 14 within a support case 15 (within which rolling bearings are mounted) or by means of universal joints or other similar means.

[0039] The two auxiliary rollers 13 shown in fig. 3 may also be longer in length or may be more than two in number adjacent to each other on the same axis of rotation.

[0040] According to a preferred feature of the invention, moreover, the rotation speed of the motor 5 and, consequently, that of the main motorised roller 8 and auxiliary rollers 13, is controlled as a function of the downward speed of the gripper 1.

[0041] In fact, once the tubular film has been accumulated on the four P 1 -P 4 grippers at the four vertices of the application frame, the latter is lowered onto the load, progressively applying the hood which unrolls from the grippers themselves, at a certain rate of descent. The descent speed may vary during the application of the hood, for example with a slower start and progressively faster run, because in the first phase there is a greater criticality both for the greater tension of the accumulated film, which tends to create loops, and for the stability of the load.

[0042] According to this preferred aspect of the invention, the rotation of the main motorised roller 8 and the auxiliary rollers 13 is controlled according to the (downward) translation speed of the grippers relative to the load.

[0043] This allows the rotation speed of the motorised roller 8 to be matched to the speed at which the hood is unrolled from the gripper 1, minimising friction or strain between the film and rollers 8, 13 which would otherwise create unwanted loops at the hood opening edge.

[0044] According to this aspect, the peripheral speed of roller 8 does not necessarily have to be the same as the translation speeds of the gripper, but the speed of roller is expected to be controlled as a function of the translation speed. For example, the peripheral speed of motorised roller 8 is slightly different, with a variable deviation, from the translation speed of the gripper.

[0045] With this method of control, it has been noted that the formation of loops is completely avoided, even in the complete absence of the supporting means of film, i.e. telescopic rods or flexible ropes of prior art.

[0046] This effect translates into a significant advantage in machine construction, which is particularly favourable in the case of rotatable grippers on a horizontal axis - as in the exemplary case illustrated - but also in the case of fixed motorised grippers.

[0047] In the operation of the gripper 1, the free leading edge of the tubular film C is inserted between the two prongs 3 and 4 and brought to rest against the main prong 3. Then the gripper 1 is closed by bringing the idler roller 11 to rest against the motorised roller 8, with a pressure determined by the actuator 10, pinching the film of the tubular hood C in the middle. At this point, the motor 5 is operated causing the movement of the belt 7 and the roller 8, which rotates counterclockwise (with respect to the plane of fig. 2) together with the auxiliary rollers 13: the film is then dragged inside the fork, accumulating on the main prong 3 between the roller 8 and the bottom portion of the fork.

[0048] In the unrolling phase, when the application frame moves down along the load to be wrapped, the film is released from gripper 1 in the opposite process to that of accumulation and with a rotation speed of rollers 8 and 13 controlled according to the translation speed of the gripper and the application frame.

[0049] Figs. 4A-4F diagrammatically show the accumulation and unrolling phases for an exemplary case, in which the motorised accumulative pegs are facing upwards and the hood is applied straight on, as in the IS44 machine produced by the same Applicant, but the pegs are in the shape of pivoting grippers on a horizontal axis.

[0050] Fig. 4A shows the phase of picking up the plastic film hood, with the grippers facing upwards (only two out of four are shown). Fig. 4B shows the phase of accumulating the hood on the grippers and Fig. 4C shows a phase of the grippers moving away from each other, with the hood being spread apart and the plastic film stretched out. In Figs. 4D and 4E the grippers perform a 180° pivoting rotation and bring the motorised rollers to the bottom. After the complete rotation, without the hood actually being reversed over, the application frame begins to translate, moving downward onto the load. In fig. 4F, the application frame has reached the lower end and the motorised rollers are coinciding with the lower base of the load.

[0051] As is clear from the above description, the hooding apparatus according to the invention perfectly fulfils the purposes set out in the introduction.

[0052] In particular, the presence of the drive belt 7 allows the rollers 8, 13 to be driven without other, bulkier transmission gears, which allows the diameter of the roller 8 to be kept very small. The working surface and the peripheral rotation speed are therefore suitable to drive the plastic film in a more regular manner, without local deformations that would cause irregularities upon unrolling.

[0053] In addition, the presence of the auxiliary rollers 13 and the speed control of all rollers 8 and 13 in proportion to the translation speed of the grippers and the application frame, results in a very regular unrolling of the tubular film, which makes it unnecessary to use supporting rods or ropes for the opening edge of the tubular film.

[0054] It is understood, however, that the invention is not to be considered limited to the particular arrangements illustrated above, which are only exemplary embodiments of it, but that several variants are possible, all within the reach of a person skilled in the art, without, however, going beyond the scope of protection of the invention itself, as defined by the following claims.

Examples

Embodiment Construction

[0024]In fig. 1B it is illustrated an exemplary hooding machine of prior art (as disclosed in EP 1 990 277), comprising a frame - arranged astride a roller conveyor on which a load to be wrapped is placed - above which it is arranged a mechanism for forming a plastic film hood C and a application frame, vertically movable, on which are installed four accumulative grippers P 1 -P 4 facing upwards and movable each other to perform a spreading movement.

[0025]The operation of this general part of the machine will not be further described here because it is known to a skilled in the field and is in any case described in EP 1 762 493 and EP 1 990 277, which are taken here as a reference.

[0026]The general configuration of the machine frame in relation to the load packing station, as well as the way the hood is formed can also be different, for example with the grippers P 1 -P 4 facing downwards as shown in EP 1 510 460.

[0027]A motorised accumulative gripper 1 is shown in cross-section in...

Claims

1. Hooding apparatus comprising a support frame, on which it is arranged a system for forming a hood (C) of tubular plastic film, and a application frame arranged to transfer said hood (C) along a translation axis along a load to be wrapped residing in a wrapping station, said application frame being provided with a plurality of accumulative grippers (P1-P(4)), each of said accumulative grippers (P1-P4) having at least one main prong (3) provided with a motorised roller (8) capable of pushing said hood film (C) to accumulate on said main prong (3) and of driving said hood film (C) to unroll from said main prong (3), characterised by what said motorised roller (8) is set in rotation by means of a belt drive (7) closed in a loop, which runs in the direction of said main prong (3), passes over idler rollers (6) and around a drive pinion (5a) of a relative motor (5) and wherein said motorised roller (8) has a main axis of rotation (a-a) and is rotationally coupled to at least one pair of auxiliary rollers (13), opposed on both sides of said motorised roller (8), having their respective axes of rotation (b-b, c-c) in the same plane of said main axis of rotation (a-a) but converging with each other by an angle (δ).

2. Hooding apparatus as in claim 1, wherein a vertex of said angle (δ) faces outwardly of said tubular hood (C).

3. Hooding apparatus as in claim 1 or 2, wherein said angle (δ) is about 90°.

4. Hooding apparatus as in any one of claims 1, 2 or 3, wherein said auxiliary rollers (13) are connected to said motorised roller (8) by bevel gears (14).

5. Hooding apparatus as in any of the preceding claims, wherein the speed of said motor (5) is variable and is controlled as a function of a translation speed of said application frame along said translation axis.

6. Hooding apparatus as in any of the preceding claims, wherein said accumulative grippers (P1-P4) are mounted on said application frame and pivoting around a horizontal axis by means of a driven motor (M).

7. Wrapping method with plastic film hood, comprising of providing a hooding machine equipped with a system for forming a hood (C) of tubular plastic film, and an application frame capable of translating said hood (C) with a translation movement along an axis of a load to be wrapped residing in a wrapping station, said application frame being provided with a plurality of accumulative grippers (P(1)-P(4)able to be mutually spread a part, each one of said accumulative grippers (P1-P4) having at least one main prong (3) equipped with a motorised roller (8) alternatively operated in a first direction of rotation to push said cap film (C) to accumulate on said main prong (3), and a second direction of rotation to drive said hood film (C) to unroll from said main prong (3), characterised by that said motorized roller (8) is driven in rotation with at least a pair of auxiliary rollers (13), opposed on both sides of said motorized roller (8), having respective rotation axes (b-b, c-c) in the same plane of rotation of a main rotation axis (a-a) of said motorized roller (8) and having angles converging between them by an angle (δ).

8. A method of wrapping with a plastic film hood as in claim 7, wherein the drive of said motorised roller (8) in said second direction of rotation is controlled as a function of a speed of said application frame during said translation movement along said load axis.

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