Station for heat-shrinking plastic film for the packaging of objects

Abstract

A heat-shrinking station (10) for the packaging of packages using heat-shrinkable plastic film comprises at least two side units (16) for emitting hot air, which are arranged on both sides of an area intended to allow the packages to pass longitudinally between an inlet and outlet. The side units (16) each comprise openings (17) for emitting hot air jets, extending vertically and directed towards each other in a direction substantially transverse to a direction between the inlet and outlet. Each side unit (16) can be tilted in the substantially transverse direction. The side units (16) can also be preferably moved towards or away from each other. A conveyor (12) may be provided for transporting the packages between the side units

Description

[0001] The present invention relates to an innovative heat-shrinking station for heat-shrinking plastic film for the packaging of objects.

[0002] Heat-shrinking stations for the packaging of objects (including large-size objects, such as crates, and also objects composed of several stacked elements, such as pallets or packages containing bricks, tiles, etc.) initially wrapped with a heat-shrinkable plastic film so as to form a package are known. The heat-shrinkable film is placed first on the object, in the form of a hood or wrapping, and the object thus wrapped reaches the heat-shrinking station where the package is subjected to a hot air flow which heat-shrinks the film onto the object so as to form the end package with the film tightly adhering to the object.

[0003] A first known type of heat-shrinking station comprises, for example, a horizontal rectangular frame which slides vertically by means of a suitable drive with, in the centre, the object covered with the film to be heat-shrunk. Each side of the frame has openings from which the hot air jets are emitted towards the centre of the frame. In this way, during the vertical sliding movement of the frame along the package the hot air strikes on each side the package and causes heat-shrinking of the plastic film onto the object.

[0004] It however should be considered that the distance between the hot-air emission openings and the walls of the package must be predefined and uniform (for example about 20 cm) so as to obtain a correct heat-shrinking action.

[0005] In some known stations the rectangular frame is therefore designed to be replaceable depending on the transverse dimensions of the packages to be processed.

[0006] In order to obtain a uniform distance between the hot air emission openings and the package without having to replace the frame when there is a variation in the dimensions of the package, frames with the sides which can displaced with respect to each other so as to be able to widen or reduce the width of the frame as required have also been proposed.

[0007] A further known type of station, which represents a more advanced version of the previous types, comprises two horizontal side bars with the hot air emission openings. The package to be heat-shrunk is placed between the horizontal side bars and these slide downwards so that the hot air strikes the two opposite side walls of the package between them. Before activating the station, the two horizontal bars may be moved towards or away from each other so as to adapt the space between them to the transverse dimensions of the package. Furthermore, a further bar, transverse to the first two bars and also vertically movable, emits hot air such that it strikes the front wall and then the rear wall of the package so as to complete the heat-shrinking operation.

[0008] Although this station is more flexible than the previous stations it may heat-shrink the film only on packages with a parallelepiped shape having vertical walls, like the prior known stations. Moreover, it has a size in plan view which is relatively large and cannot be easily accommodated along a packaging plant. In fact, the longitudinal dimension of the station must be at least equal to the maximum longitudinal dimension of the packages which are to be processed. Long packages thus result in the need for a long dimension of the station in the longitudinal direction. Moreover, once the dimensions of the station have been defined for a predefined length of the packages, packages longer than the maximum predefined size, and therefore longer than the horizontal bars on the two sides of the station, cannot be suitably processed.

[0009] Moreover, the use of the station with packages shorter than the two horizontal side bars may also result in problems, such unnecessary wasted energy due to the openings on the two horizontal bars which emit hot air even though they are not facing the side walls of the package.

[0010] The general object of the present invention is to overcome the drawbacks of the prior art by providing a heat-shrinking station which may heat-shrink in a rapid and efficient manner also packages which do not have a parallelepiped shapes with vertical walls and which have a length as required.

[0011] A further object is to provide such a station which occupies a small amount of space. In view of the said object, the idea which has occurred is to provide first and foremost, according to the invention, a heat-shrinking station for the packaging of packages using heat-shrinkable plastic film, comprising at least two side units for emitting hot air, which are arranged on both sides of an area intended to allow the packages to pass through longitudinally between an inlet and an outlet, characterized in that these two side units each comprise openings for emitting hot air jets, extending vertically and directed towards each other in a direction substantially transverse to a direction between the inlet and the outlet, and in that each side unit can be tilted in the said substantially transverse direction.

[0012] In order to illustrate more clearly the innovative principles of the present invention and its advantages compared to the prior art, an example of embodiment applying these principles will be described below with the aid of the accompanying drawings. In the drawings: Figures 1 and 2 show schematic perspective views of a heat-shrinking station provided in accordance with the invention, respectively from the package inlet side and package outlet side; Figure 3 shows a schematic front elevation view of the station according to Figures 1 and 2; Figures 4 and 5 show, respectively, a schematic plan view and schematic side view of the station according to the preceding figures.

[0013] With reference to the figures, these show a possible embodiment according to the invention of a station, denoted generally by 10, for heat-shrinking heat-shrinkable plastic film arranged beforehand on objects to be packaged so as to form a wrapped package.

[0014] The station 10 comprises an inlet for the packages (for example on the side shown in Figure 2) and an outlet for the packages (for example on the opposite side, shown in Figure 1) and an area intended to allow the packages to pass through and situated between the inlet and outlet.

[0015] The objects (crates, pallets with stacked products, etc,) which are conveyed into the station 10 have already been covered, at least partially, with the heat-shrinkable film in a known covering station (not shown), for example a station for performing wrapping with strip film or a station for performing hooding with tubular film, using techniques and methods which are well-known to the expert.

[0016] Below, the term "longitudinal" will be understood as meaning the direction of movement of the packages through the station between the inlet and outlet and the term "transverse" as meaning the direction transverse thereto. The longitudinal direction, i.e. the direction transverse to the vertical direction, will form a set of three Cartesian axes X, Y and Z, as schematically shown in Figure 1. The term "lateral" or "side" will be understood as meaning a position located on one side of the longitudinal path of movement of the packages.

[0017] For the longitudinal movement of the packages through the station between the inlet and outlet a known conveying line, or in short conveyor, 12, may be preferably present.

[0018] The conveying line 12 may be of any known type considered to be suitable and will therefore not be described or shown in detail. It in general may comprise a support surface on which the products are placed in order to be transported to the station 10 and / or through the station 10. The transport line 12 may be advantageously formed for example by means of a belt or chain conveyor with rollers for supporting and conveying the objects.

[0019] The station 10 comprises two side units 16 for emitting, upon command, hot air at the temperature suitable for heat-shrinking the heat-shrinkable film. Said temperature will depend on the characteristics of the heat-shrinkable film, as is well-known to the person skilled in the art. For example, it may be around 100-150°C.

[0020] The hot air units 16 are advantageously a mirror image of each other.

[0021] Each unit 16 extends vertically (along a generic axis 24 thereof) and has, for example, a vertically very long parallelepiped box shape. Each unit 16 further comprises one or more openings 17 for emitting hot air jets, extending vertically along the unit so that the two units 16 facing each other direct the air jets towards each other in a direction substantially transverse to the direction of the movement of the packages between the inlet and outlet passing between the two units 16.

[0022] Below the term "air jet" is understood as meaning an air flow preferably directed in a plane, even though relatively diverging on both sides of said plane and even if formed by several air flows superimposed on each other and / or alongside each other, so as to form a general air stream which is wide in a direction transverse to the direction of the emission and has a relatively small thickness in the direction perpendicular to said transverse direction.

[0023] The two units 16 therefore face each other so as to direct the hot air jets so that they strike the two opposite sides of a package which passes through the station in the longitudinal direction. In other words, the two units 16 essentially create preferably a vertical hot air barrier through which the object previously lined with a heat-shrinkable film is made to pass.

[0024] For emission of the hot air, the units 16 for example may comprise or be connected to hot air generators provided with heaters of the type known per se, for example electric type, or gas burners, etc., which may be easily imagined by the person skilled in the art and therefore are not shown in detail. Blowers 18 may also be provided for producing the hot air flow which crosses the heaters and is then emitted through the vertical openings 17. The heaters may be located for example inside the box-shaped structure of the units 16 and the blowers may be mounted at one end of each unit 18 so as to introduce there the air from the outside which is thus heated as it flows inside the unit 16 before being emitted from the openings 17, for example formed as elongated slits on a long wall of the unit 16.

[0025] Each side unit 16 can be tilted in the direction substantially transverse to the station. The station may be made both so as to have only a positive inclination with respect to the vertical, namely with the top ends of the two units which are closer to each other than the bottom ends and to have a positive inclination and, conversely, a negative inclination, namely with the top ends of the two units which are further away from each other than the bottom ends.

[0026] Moreover, the units 16 may also be advantageously displaceable transversely with respect to the station so that they can be moved towards or away from each other so as to reduce or widen the space between them intended to allow the packages to pass through the station.

[0027] If required, a further movement of the units 16 may also be in the vertical direction in order to raise or lower them.

[0028] In order to support the various components, the station 10 may advantageously comprise a frame or gantry 11 through which the packages to be processed pass in sequence and which defines the transit area.

[0029] In turn, the frame 11 may comprise advantageously two lateral uprights 13 and 14, each of which may support in an inclinable manner one of the two side units 16. Preferably, the frame 11 may also comprise a top cross-piece 15 which connects together the two uprights at their top ends transversely with respect to the station.

[0030] In the embodiment shown in the figures, each unit 16 may be for example supported by a beam 19, which is preferably parallel to the axis 24 of the unit and which is rotatable in the transverse plane of the station.

[0031] For the rotational movement, carrier shoes 20, 21 may be provided (in particular, preferably two carrier shoes for each unit (16), these having hingeably mounted thereon the beams 19 which slide on suitable guides 22, 23 supported on the respective uprights 13, 14. The movement of the carrier shoes 20, 21 along the guides may allow both the inclination of the beams 19, and therefore of the units 16 thereon, and their horizontal translation.

[0032] The rotational, translational or also rotary-translational movement of the units 16 will depend on the extent and the direction of the relative movement of the carriages on the respective guides.

[0033] If required, each beam 19 may also be made in the form of rail for allowing the units 16 to slide along it so as to obtain also a possible vertical movement of the units 16.

[0034] For the various movements, suitable drive systems (for example electric or pneumatic drives) known per se may be wholly or partly provided, said systems being able to be operated manually or by means of control systems which can be activated by an operator or also by means of automatic control systems with suitable sensors for detecting the size and shape of the incoming packages, so as to prepare the station to receive them.

[0035] The movement of the package and hot air emission units is in any case understood generally as being a relative movement of the package and units. In fact, although the package may be moved through the station by means of the conveyor, in a variation of embodiment of the invention, the package may also be kept stationary (or semi-stationary) and may be the station which moves longitudinally along a section of the package, for example by means of motorized carriages 38 along longitudinal rails 39, as shown schematically in broken lines in Figure 2.

[0036] The various relative movements, approach movements, inclination movements and, if necessary, vertical translation movements of the units may therefore be manual, semi-automatic or automatic, as may be easily imagined by the person skilled in the art, for example also depending on the frequency of the passing movements of packages of different shapes and sized and the need for more or less rapid adaptation of the station to the change in shape and size of the packages.

[0037] Advantageously, if required, the units 16 may also be designed so as to be rotatable, upon command, about their axis 24 so as to direct their hot air jets in the longitudinal direction. As a result, it is possible for example with the air jets to "sweep over" the side walls of the packages or also strike with the air jets the side walls of the packages in a direction which is not perfectly perpendicular, if it is considered necessary to improve the effect or the uniformity of heat-shrinking of the film. The orientation of the hot air jets in the longitudinal direction may also have the function of striking with them at least partially the front and rear walls of the package and performing with the units 16 heat-shrinking of the film also on these walls.

[0038] The orientation of the hot air jets may also be obtained by providing suitable deflectors (which are also directable if necessary) located on the air emission openings, without rotating the entire unit 16.

[0039] In any case, the orienting movement may be performed by suitable actuators (for example pneumatic pistons or electric actuators indicated by way of example by 25 in the figures).

[0040] The units 16 may also be formed along their vertical length as two segments (as can be seen by way of example indicated by 16a or 16b in the figures) or also more than two segments, which are independent of each other or partially independent depending on requirements, in terms of both hot air emission and orientation.

[0041] For example, the emission of hot air may be performed, upon command, by only one or more than one of the segments of each unit 16, depending on the height of the package and / or the position of the heat-shrinkable film on the package. In this case, suitable deflectors 26 may also be provided on the units in order to direct the flows of hot air only in the areas in the vicinity of the corresponding segment.

[0042] If required, the rotation about the axis 24 may also be performed separately for each segment.

[0043] As is clear, with the movements described for the units 16 it is possible to adapt the position of the hot air emission openings so that the distance between them and the walls of the package may be kept at a distance considered optimum for heat-shrinking the film while the package passes through the station and the film is heat-shrunk.

[0044] If required or preferable, a further hot air emission unit for heat-shrinking, indicated by 27 in the figures, may also be provided, being arranged transversely and vertically movable.

[0045] Said transverse unit 17 may be useful, for example, when the packages to be treated are too wide in the transverse direction to allow the hot air flows of the units 16 - even though suitably oriented about their axis 24 - to reach effectively the entire front face and / or rear face of the package for correct heat-shrinking of the film on said faces, or even if the feature of orientability of the units 16 about their axis 24 is not required (for example in order to avoid the need for complex mechanisms which enable such orientability of the units 16).

[0046] The unit 27 (which may also be per se similar to the side units 16) has a hot air emission opening 28 which is transverse to the station so as to form a hot air jet extending transversely with respect to the station. The unit 27 is designed so as to be vertically slidable, upon command, such that its air jet is able to pass along the front and / or rear vertical wall of the package conveyed into the station.

[0047] In the same way as for the units 16, the unit 27 may comprise or be connected to hot air generators which may comprise for example advantageously heaters of the type known per se, for example electric type, or gas burners, etc., which may be easily imagined by the person skilled in the art and therefore are not shown in detail. In the same way as for the units 16, these heaters may be inside the unit 27 (which is advantageously box-shaped). A blower 33 may also be provided for producing the hot air flow which crosses the heaters and is then emitted through the horizontal opening 28. Said blower 33 may for example be located at one end of the unit 27 in order to blow air inside the unit, said air, once heated, emerging as a hot air jet from the opening 28 which is formed for example as a horizonal slit in a wall of the unit 27. Advantageously, the unit 27 is made so as to be rotatable about a horizontal axis 29, which is transverse to the station, so as to be able to direct its air jet both towards the font and the towards the rear of the station in the longitudinal direction.

[0048] In this way, a single transverse unit with a single air jet may perform heat-shrinking of the film both on the front face and on the opposite rear face of the package, suitably moved through the station.

[0049] The rotation may direct the air jet until it is horizontal in a direction towards the inlet and / or the outlet of the station. If preferred, the rotation may also be limited so that the air jet reaches, at the two ends of the movement, a position inclined downwards in either direction.

[0050] With rotation of the unit 27 about the transverse axis 29, the air jet may be directed first onto the front face of the package entering the station and them, rotating about its axis 29, onto the rear face of the package exiting the station. Owing to the vertical movement of the unit, the air jet may pass along the corresponding face of the package so as to heat-shrink the film onto said face.

[0051] Rotation of the unit 27 may be obtained by means of a specially designed actuator 34, for example a pneumatic piston or an electric actuator.

[0052] In order to perform the movement of the unit 27, the unit 47 may, as can be seen more clearly in Figure 2, be supported on a cross-piece 30 which, by means of its own drive, may slide vertically along vertical rails 31 and 32, for example advantageously supported on the uprights 13 and 14.

[0053] For rotation, the unit 27 may have its axis 29 which is supported on the cross-piece, and the actuator 34 may be arranged between the cross-piece and unit.

[0054] In order to provide power to the unit 27 a flexible chain guide 35 containing electric cables, fluid supply pipes, etc., allowing the vertical movement of the unit, may be used.

[0055] The operation of the station may be controlled by a suitable control unit, schematically indicated by 36 in the figures. The control unit may also be arranged separate from the station and in the vicinity thereof or also be formed by a first part close to or inside the station (for example, with gas treatment units, valves, pressure switches, pressure gauges, relays, etc.) and a separate cabinet or ledge with the control and operating systems for an operator. The control unit is for example made with an electronic programmed logic or wired system, in a manner known per se which may therefore be easily imagined by the person skilled in the art based on the description of the station provided here. Said control unit may also be connected to or comprise a command terminal for the user and be connected to suitable sensors, known per se and therefore not shown in detail, for example in order to detect the dimensions of the incoming package and suitably control the station to move the hot air emission units and preset it to suitably perform heat-shrinking of the film on the package. For example depending on the transverse dimension of the package to be treated, the vertical side units may be displaceable in the transverse direction and if necessary can be tilted, in the same way that the horizontal transverse unit 27 (where present) may be displaceable in the vertical direction so as to be arranged at the correct distance from the walls of the package. Packages (indicated generally by 37 in Figure 3) with different shapes and sizes may thus be adequately processed, as schematically shown in broken lines in Figure 3.

[0056] In particular, packages with inclined side walls as well as packages with a parallelepiped shape with the walls on the four vertical sides may also be properly processed. In general, packages with a base width different from that of the top side may be easily processed.

[0057] The station allows for example the efficient and adequate heat-shrinking of the heat-shrinkable film for covering packages formed with sheet-like products inclined on opposite sides of special support trestles. These packages are for example used for sheets of glass, thin sheets of lining material and the like.

[0058] The control unit 36 may also follow suitable programmed cycles so that the air jets are directed towards the various walls of the package, while the latter is suitably positioned inside the station 10.

[0059] During use, the station may be for example provided with the two side units arranged at the correct distance from each other and if necessary inclined depending on the walls of the incoming package. This arrangement may also be realized manually before the station is activated.

[0060] When a package reaches the station the advancing movement of the package in relation to the side units 16 may cause heat-shrinking of the film. If present, the horizontal unit 27 (where present) may be initially in a raised position and, when a package arrives and is positioned, via the conveyor 12 and / or by means of a longitudinal movement of the station, with its front face at the longitudinal distance from the horizontal unit 27 considered correct for heat-shrinking the film, said unit 27 may be operated, directed towards the front face of the package and slid vertically so as to heat-shrink the film on the front face of the package.

[0061] Once said heat-shrinking operation has been performed, the horizontal unit 27 may be repositioned and immobilized in its raised position so as to allow the package to advance passing below it, while the heat-shrinking side units perform heat-shrinking of the side faces of the package passing between them. Once the rear face of the package has passed beyond the horizontal unit 27 by the correct distance, said unit 27 may be operated again, directed towards the rear face of the package and slid vertically so as to heat-shrink the film also on the rear face of the package.

[0062] If required, during the relative advancing movement of the package underneath the horizontal unit 27, the horizontal unit 27 may in any case be operated directed downwards so as to heat-shrink, if necessary, a heat-shrinkable film which may cover the top side of the package.

[0063] Once the film on the package has been correctly heat-shrunk, the package may leave the station and the station may prearrange itself or be preset to receive the next package.

[0064] At this point it is clear how the objects of the invention have been achieved.

[0065] Thanks to a heat-shrinking station designed in accordance with the principles of the present invention it is possible to adequately process packages of different shapes and sizes. The packages may be not only packages with vertical walls, but also packages with inclined walls as required. The packages may have a base of the package which is larger or smaller than the top face.

[0066] In the case of packages which are sufficiently narrow in the transverse direction, the side units 16 may also be sufficient to heat-shrink the film both on the side walls (inclined or not inclined) and on the front and rear walls (also inclined or not inclined) and also, if need be, on the top face of the package.

[0067] Alternatively or in addition, a horizontal heat-shrinking unit 27 may be provided for heat-shrinking the film on the front and rear faces of a package.

[0068] A longitudinal relative advancing movement of the package with respect to the horizontal unit (by means of the conveyor which moves the package or the station which travels on the carriages 38, or a combination of the two if both are present), synchronized with the vertical movement of the horizontal unit 27 (where present) via the control unit, may also allow the unit 27 to be kept at the correct and substantially uniform distance from the front and rear walls of the package even if they are also inclined.

[0069] If desired or required, a further synchronized movement of the conveyor or the station and of the horizontal unit (where present) may allow heat-shrinking of a film also on the top face of the package, whether or not it is also horizontal.

[0070] In the case where the side units are formed with segments which can be singly activated, as described here by way of example, the station may also process packages with a different height or with a covering film located at different heights, without wasting energy in order to heat the air flows situated at heights where they are not required.

[0071] In any case, the plan-view size of the station depends in the transverse direction on the maximum width of the packages which are to be processed, while in the longitudinal direction it may depend on the longitudinal thickness which is to be given to the station (for example due to the thickness of the heat-shrinking units and / or of the support frame), but not necessarily on the longitudinal dimensions of the packages to be processed, which may be of any nature.

[0072] In particular, in the case of packages which are moved by means of the conveyor, the station according to the invention may in fact process packages with any longitudinal dimension and the longitudinal dimension of the station may be independent of the longitudinal dimension of the package.

[0073] The surface area occupied by a packaging plant owing to the heat-shrinking station according to the invention may thus be kept very small.

[0074] Obviously the description given above of embodiments applying the innovative principles of the present invention is provided by way of example of these innovative principles and must therefore not be regarded as limiting the scope of the rights claimed herein.

[0075] For example, the station may have a different form (for example the frame may be made only with the vertical uprights and without the horizontal cross-piece) and different systems for orienting the flows of hot air. In particular, both the side units and top horizontal unit, if present, may have movable deflectors or rotating nozzles for directing the flow towards the faces of the package instead of them being fully oriented. The movements of the various parts of the station may be manual or motorized or automated depending on the specific requirements or wishes, as may now be easily understood by the person skilled in the art based on the description provided here.

[0076] Instead of a rotational movement, the horizontal unit may also comprise openings for emitting the hot air both towards the front and towards the rear of the package, which can be selectively activated depending on the package face to be processed.

[0077] Finally, the dimensions, proportions and form of the station may be different depending on the specific requirements and the particular forms and dimensions of the objects to be packaged.

Claims

1. Heat-shrinking station (10) for the packaging of packages using heat-shrinkable plastic film, comprising at least two side units (16) for emitting hot air, which are arranged on both sides of a receiving area intended to accommodate the packages between an inlet and an outlet, characterized in that said side units (16) each comprise openings (17) for emitting hot air jets, extending vertically and directed towards each other in a direction substantially transverse to a direction between the inlet and outlet, and in that each side unit (16) can be tilted in said substantially transverse direction.

2. Station according to claim 1, characterized in that the two side units (16) are movable in a transverse direction towards and away from each other.

3. Station according to any one of the preceding claims, characterized in that the side units (16) can be oriented so as to emit the hot air jets in the direction towards the outlet and / or towards the inlet.

4. Station according to any one of the preceding claims, characterized in that the side units (16) are formed by vertical segments (16a, 16b) which can be independently activated.

5. Station according to any one of the preceding claims, characterized in that the side units (16) are box-shaped and contain hot air heaters and have a blower (18) at one end for blowing air inside them and emitting hot air from said openings (17).

6. Station according to any one of the preceding claims, characterized in that it comprises a frame with two lateral uprights (13, 14) each supporting one of the two side units (16).

7. Station according to the preceding claim, characterized in that each side unit (16) is supported by a beam (19) hingeably mounted on carrier shoes (20, 21) which slide on guides (22, 23), supported on the respective lateral uprights (13, 14) so as to produce the tilting movement of the side unit and / or a movement of the two side units towards and away from each other.

8. Station according to any one of the preceding claims, characterized in that it comprises a horizontal unit (27) for emitting hot air, which is arranged transversely with respect to the area intended to allow the packages to pass through longitudinally and is vertically movable.

9. Station according to the preceding claim, characterized in that the horizontal unit (27) can be controlled to emit a hot air jet in a longitudinal direction towards the outlet or towards the inlet.

10. Station according to the preceding claim, characterized in that the horizontal unit (27) can be rotated upon command about a horizontal axis (29) so as to emit the hot air jet in the longitudinal direction towards the outlet or towards the inlet.

11. Station according to claim 6 and at least one of claims 8, 9 and 10, characterized in that the horizontal unit (27) slides along vertical rails (31, 32) on the lateral uprights (13, 14).

12. Station according to any one of the preceding claims, characterized in that it comprises a conveyor (12) intended to move packages through said area between the inlet and outlet.

13. Station according to any one of the preceding claims, characterized in that it comprises carriages (38) for moving the station in a longitudinal direction along the package receiving area.

14. Station according to claims 8 and 12 and / or 13, characterized in that a control unit (36) is connected so as to control the movement of the horizontal unit (27) and the conveyor (12) and / or the carriages (38), for a synchronized movement, in the sense of moving the horizontal unit (27) vertically, directing its air jet along a front side and then along a rear side of a package in the receiving area.

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