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Title:
METHOD AND APPARATUS FOR PROCESSING A SHEET OR SHEETS OF THERMOPLASTIC MATERIAL HAVING CROSS-SECTION WITH A HOLLOW PROFILE
Document Type and Number:
WIPO Patent Application WO/2018/166968
Kind Code:
A1
Abstract:
The present invention relates to a method for processing a sheet or sheets of a thermoplastic material (10) having cross-section with a hollow profile characterized in that said sheet(s) is preheated in a preheating station (3) on the surface at a temperature not exceeding that resulting in a softening without substantially compromising the hollow inner structure of said thermoplastic material having cross-section with a hollow profile, before being subjected to at least one next processing such as a lamination in a lamination station (4), welding-sealing, thermoforming in a thermoforming station (5), creasing, surface treatment in a surface treatment station (6), printing, cutting in a cutting station (7) or combinations of these processes. The invention also relates to an apparatus implementing the above-mentioned method.

Inventors:
TERRAGNI MASSIMO (IT)
PERRELLA DANIELE (IT)
Application Number:
PCT/EP2018/056079
Publication Date:
September 20, 2018
Filing Date:
March 12, 2018
Export Citation:
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Assignee:
AGRIPAK S R L (IT)
International Classes:
B32B37/20; B29C35/02; B29C35/10; B29C37/00; B29C43/02; B29C43/20; B29C47/00; B29C51/08; B29C51/10; B29C51/26; B29C51/42; B29C69/00; B29C35/08; B29C45/14; B29C65/00; B29K23/00; B29K67/00; B29K69/00; B29K71/00; B29K105/04
Domestic Patent References:
WO2009103981A12009-08-27
WO1992011121A21992-07-09
WO2002099218A12002-12-12
Foreign References:
EP2497945A12012-09-12
Other References:
None
Attorney, Agent or Firm:
ZAMBARDINO, Umberto (IT)
Download PDF:
Claims:
CLAIMS

1. Method for processing a sheet or sheets of thermoplastic material having cross-section with a hollow profile, the method comprising the steps of:

- feeding said sheet(s) of thermoplastic material to a preheating station (3; 3a) and preheating said thermoplastic material in correspondence of at least one of its opposite surfaces, preferably on both of its opposite surfaces, at a temperature not exceeding that resulting in a softening of said at least one of the two opposite surfaces without substantially compromising the hollow inner structure of said sheet(s) of thermoplastic material having cross-section with a hollow profile,

- subjecting said preheated sheet(s) of thermoplastic material to at least one processing selected from the group consisting of lamination, welding- sealing, thermoforming, creasing, surface treatment, printing, cutting or combinations thereof. 2. Method according to claim 1 , wherein said thermoplastic material having cross-section with a hollow profile consists of a plurality of separate sheets and said method is carried out in batches by feeding said sheets in sequence to said preheating station (3; 3a).

3. Method according to claim 1 , wherein said thermoplastic material having cross-section with a hollow profile consists of a tape (10) of sheet of thermoplastic material having cross-section with a hollow profile and said method is carried out continuously by feeding said tape (10) to said preheating station (3; 3a).

4. Method according to claim 3 wherein said tape (10) of sheet of thermoplastic material having cross-section with a hollow profile comes from a reel (8), and said method comprises the steps of:

- unwinding said tape (10) of sheet of thermoplastic material having cross- section with a hollow profile from said reel (8),

- feeding said unwound tape (10) to a preheating station (3; 3a) and preheating said thermoplastic material in correspondence of at least one of its opposite surfaces, preferably on both of its opposite surfaces, at such a temperature as to eliminate a warp of said tape resulting from the previous winding on the reel (8) and in any case not exceeding that resulting in a softening of said at least one of the two opposite surfaces without substantially compromising the hollow inner structure of said thermoplastic material having cross-section with a hollow profile, thereby obtaining a substantially flat tape (10) of sheet of thermoplastic material having cross-section with a hollow profile,

- subjecting said substantially flat and preheated tape (10) to at least one processing selected from the group consisting of lamination, welding- sealing, thermoforming, creasing, surface treatment, printing, cutting or combinations thereof.

5. Method according to claim 3 or 4, wherein said preheating is carried out on said opposite surfaces of the unwound tape (10) of the thermoplastic material having cross-section with a hollow profile at different temperatures, preferably higher in correspondence of the convex surface of the curved unwound tape and lower in correspondence of the concave surface of said curved unwound tape.

6. Method according to any one of the preceding claims, wherein the preheating temperature of said at least one surface of the thermoplastic material having cross-section with a hollow profile is comprised between 100°C and 500°C and, in case of use of different temperatures for preheating the opposite surfaces of the tape ( 10) of thermoplastic material having cross-section with a hollow profile, the temperature difference is comprised between 1°C and 250°C.

7. Apparatus (1 ;30;40) for processing a sheet or sheets of thermoplastic material having cross-section with a hollow profile, the apparatus comprising:

- a preheating station (3,3a) for said sheet(s) of thermoplastic material having cross-section with a hollow profile, the preheating station (3,3a)comprising at least one heating device (12, 13), preferably a pair of opposite heating devices (12, 13), each comprising at least one heating group, preferably more heating groups composed in turn of at least one heating element, preferably more heating elements operable independently to heat at least one surface, preferably the opposite surfaces of said sheet(s) of thermoplastic material having cross-section with a hollow profile independently at a predetermined temperature,

- at least one processing station (4,5,6,7,31 ,41) for the preheated thermoplastic material having cross-section with a hollow profile exiting from the preheating station (3,3a), said at least one processing station being selected from the group consisting of the lamination (4), welding-sealing (5;31), thermoforming (5), creasing (31), surface treatment (6), printing (41), cutting (7) station or combinations thereof,

- means for feeding said sheet(s) of thermoplastic material having cross- section with a hollow profile in said preheating station and means for feeding the sheet(s) of preheated thermoplastic material exiting from the preheating station to said at least one processing station.

8. Apparatus (1 ;30;40) according to claim 7, wherein said feeding means to the preheating station comprise a loading station of stacked sheets.

9. Apparatus (1 ;30;40) according to claim 7, wherein said feeding means to the preheating station comprise at least one reel (8), preferably a pair of independent reels (8), on which a tape (10) of sheet of thermoplastic material having cross-section with a hollow profile is wound and means for unwinding said tape of sheet of thermoplastic material having cross-section with a hollow profile from the at least one reel (8), as well as preferably means for replacing empty reels with full reels.

10. Apparatus (1 ;30;40) according to any one of claims 7 to 9, wherein said at least one heating device (12; 13) has zones that can be preheated independently from the heating elements, means for adjusting the preheating of such zones being also provided in order to preheat mainly or exclusively zones of said at least one heating device (12, 13), in particular middle zones of said at least one heating device (12, 13) which in use are facing towards corresponding zones of the thermoplastic material having cross-section with a hollow profile to be prepared, through said preheating, to the next processing in said at least one processing station (4,5,6,7,31 ,41).

Description:
Title: Method and apparatus for processing a sheet or sheets of thermoplastic material having cross-section with a hollow profile

DESCRIPTION

Field of application In its more general aspect, the present invention relates to the field of thermoplastic material processing.

In particular, the present invention relates to a method for processing a thermoplastic material having cross-section with a hollow profile, in order to obtain, preferably but not exclusively, die-cut packages, panels playing the role of covering/ heat/ sound insulation and support, office supplies, advertising billboards and templates of display units for products or in any case for other applications of any shape in thermoplastic material with a hollow profile. That method can be carried out both in batches, for example on single sheets of a thermoplastic material having cross-section with a hollow profile, and continuously for example on a tape of sheet of thermoplastic material having cross-section with a hollow profile.

The present invention also relates to an apparatus for processing a sheet or sheets of thermoplastic material having a section with a hollow profile which uses that method for the above-mentioned aims. Prior art

The use of thermoplastic materials, such as for example polypropylene (PP), polycarbonate (PC), expanded polypropylene (PPE), high density polyethylene (HDPE) and polyethylene terephthalate (PET), in the form of sheets having cross-section with a hollow profile with alveolar geometries (corrugated, twin wall, hollow profile, etc.), honeycomb-like and air bubblelike (bubbleguard), in different thicknesses, densities, colours and shapes, is becoming more and more established in all those applications in which it is desired to join the advantages of extreme weight limitation with those typical of those materials. In particular in those materials, being density and thickness directly proportional, above 8- 10 mm of thickness they are most used for applications requiring higher mechanical properties (such as for example in constructions), while below that thickness they are employed in several applications in particular in packaging, preservation, heat and/ or sound insulation, waterproofing, covering, floating structures, handling and storage and printing.

Among the fields in which the above-mentioned thermoplastic materials having cross-section with a hollow profile are most employed one can mention for example:

- Food processing (boxes and packaging for fruit, vegetables, meat, fish, crustaceans, molluscs etc.)

- Industrial logistics (reusable boxes, retaining walls for box pallets, pallets, interlayer panels etc.)

- Automotive, wherein they can play several roles among which covering, heat and/ or sound insulation, support (parcel shelf panels, boot lining, door interior, body deck insulation etc.)

- Advertising (billboards, display units for products etc.)

- Pharmaceutical chemistry (boxes/ packaging for vials, glass containers etc.)

- Textile (boxes and packaging for packing bed sheets, blankets, sweaters etc.)

- Building (boxes for tiles, footing forms, sheets for wall and floor waterproofing, drainage panels etc.)

- Agriculture (covers for greenhouses, protections for plants and flowers, soil containers etc.) - Linen (rear protection panels for electrical household appliances etc.)

- Stationery (folders - rigid office briefcases etc.)

- Waste management (containers for hospital waste and separate collection etc.) - Boating (platforms and floating constructions in general, hulls for boats like motorboat, kayak, sailing boat, catamaran etc.)

In fact, the above-mentioned thermoplastic materials in the form of sheets having cross-section with hollow-profile with alveolar geometries (corrugated, twin wall, hollow profile, etc .), honeycomb-like and air bubble-like (bubbleguard) are able to replace the more traditional ones, such as e.g. cardboard, foam polystyrene (EPS), fiberglass and wood, allowing several additional advantages among which in particular high mechanical features, low specific weight and resistance to water, perforations, chemical agents, micro-organism development, high/low temperatures and UV rays.

Moreover, the above-mentioned thermoplastic materials do not chip thus avoiding possible wounds to the operator during the handling steps and they usually do not leave residues that must then be eliminated with a subsequent increase in process times and costs.

Having a cross-section with hollow profile, those materials are generally also lighter than the above-mentioned traditional ones with the same thickness.

Moreover, it is possible to print the surface thereof through a silk-screen, flexographic or digital technique allowing effects having a higher quality than traditional materials to be obtained.

In those cases where the goods must be stored, handled, processed and transported through a cold chain (e.g. for fish and/ or meat), those materials are preferable to those with higher heat-insulating properties such as for example foam polystyrene (EPS) since they allow the content to be brought more fastly at a low temperature.

Moreover, unlike EPS, the above-mentioned thermoplastic materials having cross-section with a hollow profile not treated with glues or solvents are fully recyclable and they can be employed in the extrusion process in extremely high percentages that can reach about 90% as a function of the type of application with subsequent saving of raw material purchase costs and encouraging environmental protection.

At present, the above-mentioned thermoplastic materials are obtained through suitable extrusion processes and related apparatuses which, starting from the thermoplastic raw materials, allow a continuous sheet to be obtained in the form of a tape of thermoplastic material having cross- section with a hollow profile exiting from suitable extrusion dies with a density and thickness that can be originally predetermined, for example establishing and adjusting process parameters such as in particular the feeding flow rate and quantity of the thermoplastic raw materials, the extrusion temperature etc..

Afterwards, that continuous sheet having cross-section with a hollow profile is subjected to a sequential palletization step of the manual or automated type wherein it is cut transversely and in case also longitudinally in order to get single sheets which can be subjected to next treatments in order to obtain for example products like containers and/ or packages intended for use in the above-mentioned applications. In particular, in the case of treatments after extrusion (e.g. printing, lamination, welding-sealing, thermoforming, creasing, surface treatment, cutting etc.) carried out on the above-mentioned thermoplastic materials having cross-section with a hollow profile to obtain packages and/ or containers or for other applications of any shape such as for example those mentioned above in the present description, the above-mentioned single sheets are fed in batches, or one at a time, to the respective processing station/step. In particular, a welding-sealing/ creasing step of the edges of the die-cut product is also associated to the thermoforming step that can be carried out by the same thermoforming station where it is equipped with welding means or in a separate welding- sealing and creasing station placed downstream of the thermoforming apparatus between the thermoforming apparatus and the cutting station/ apparatus.

The welding-sealing and creasing of the profiles of the above-mentioned thermoplastic materials allows in fact some ameliorative features to be obtained with various subsequent advantages, particularly remarkable for packages, but not only, among which the fact that they are liquid-tight thus allowing a transport, handling and storage which are always clean and compatible with other goods. Moreover, in the case where the contents of the above-mentioned packages and applications in general are particularly susceptible to hygienic problems and/or of floatability, the welding-sealing avoids possible insertions of foreign bodies, dust, liquids, bacteria, mildews etc. within the recesses of the profile. Furthermore, the air contained within the recesses of the profile, with the same thickness being used, increases the rigidity of the surfaces (in terms of higher mechanical resistance to compression and flexion, shocks and perforations) allowing 1) the use of lower thicknesses thus saving the raw material in the production step, 2) a higher load capacity if compared with a similar package with an unsealed hollow profile and if compared with a traditional package of the same size in EPS, allowing thus load storage and transport costs to be saved, 3) better heat-insulating properties if compared to a similar package with an unsealed hollow profile, and in any case if compared with cardboard packages of equal thickness, when being outside the cold chain and 4) a higher content cooling speed if compared with a traditional package of the same size in EPS, when being inside the cold chain. However, the result of the treatments of the single sheets of thermoplastic material having cross-section with a hollow profile as indicated above appears to be often unsatisfactory specially where processing materials with a hollow profile with relatively high densities and thicknesses, such as for example densities of 500 g/ mm 2 or higher. In this case it is observed in fact that the above-indicated treatments such as in particular welding-sealing, thermoforming and cutting appear to be difficult often obtaining at the end of the processing products of poor quality or completely unusable.

Moreover, since the above-mentioned treatments are of the batch type, they require a loading system of the single sheets on the feeding line to the processing machine that appears though to be complex per se. Moreover, it must be noted that the above-mentioned processing of the batch type has also an advance system of the single sheets that usually materializes in pliers for grasping and moving those sheets from the loading zone to the next processing stations, adding further complexity. That loading and advance system, besides requiring the sheets to be supplied in the loader by an operator, appears often to be also inaccurate so that it can happen that the sheets are fed to the machine in a wrong position and/ or quantity with the subsequent need for a continuous supervision of the feeding step, possible interruptions and production waste. In view of the above it is hence evident that the above-mentioned batch processing has also disadvantageously an unsatisfactory production efficiency (yield), additional labour costs as well as the real possibility of a considerable quantity of production waste. The main aim of the present invention is hence to provide a method and a related apparatus for processing thermoplastic materials having cross- section with a hollow profile in order to obtain preferably but not exclusively templates / die-cut containers / packages which overcome or at least reduce the above-mentioned drawbacks with reference to the prior art. Summary of the invention

That aim is achieved by the invention, primarily, by a method for processing a sheet or sheets of thermoplastic material having cross-section with a hollow profile, the method comprising the steps of:

- feeding said sheet(s) of thermoplastic material to a preheating station and preheating said thermoplastic material in correspondence of at least one of its opposite surfaces at a temperature not exceeding that resulting in a softening of said at least one of the two opposite surfaces without substantially compromising the hollow inner structure of said sheet(s) of thermoplastic material having cross-section with a hollow profile, - subjecting said preheated sheet(s) of thermoplastic material to at least one processing selected from the group consisting of lamination, welding- sealing, thermoforming, creasing, surface treatment, printing, cutting or combinations thereof.

Preferably, in the above-mentioned method, the preheating is carried out on both of the opposite surfaces of the sheet(s) of thermoplastic material having cross-section with a hollow profile.

According to an embodiment of the invention, the above-mentioned thermoplastic material having cross-section with a hollow profile consists of a plurality of separate sheets and said method is carried out in batches by feeding said sheets in sequence to said preheating station.

According to another particularly preferred embodiment, said sheet(s) of thermoplastic material having cross-section with a hollow profile consists of a tape of sheet of thermoplastic material having cross-section with a hollow profile and said method is carried out continuously by feeding said tape to said preheating station. That tape of sheet of thermoplastic material having cross-section with a hollow profile can come for example from a feeding reel or it can come directly from an extrusion or printing apparatus, in that case the preheating station being substantially placed in line with the extrusion die of that extrusion apparatus or in line with the exit of the printing apparatus.

When feeding a tape of sheet of thermoplastic material having cross-section with a hollow profile coming from a reel, the method according to the invention preferably comprises the steps of:

- unwinding said tape of sheet of thermoplastic material having cross- section with a hollow profile from the reel,

- feeding said unwound tape to a preheating station and preheating said thermoplastic material in correspondence of at least one of its opposite surfaces at such a temperature as to eliminate a warp of said tape resulting from the previous winding on the reel and in any case not exceeding that resulting in a softening of said at least one of the two opposite surfaces without substantially compromising the hollow inner structure of said tape of thermoplastic material having cross-section with a hollow profile, thereby obtaining a substantially flat tape of sheet of thermoplastic material having cross-section with a hollow profile,

- subjecting said substantially flat and preheated tape to at least one processing selected from the group consisting of lamination, welding- sealing, thermoforming, creasing, surface treatment, printing, cutting or combinations thereof.

Preferably, in the above method preheating is carried out on said opposite surfaces at different temperatures, preferably higher in correspondence of the convex surface of the curved unwound tape and lower in correspondence of the concave surface of said curved unwound tape.

Preferably, in the method according to the invention, the preheating temperature of said at least one surface of the thermoplastic material having cross-section with a hollow profile is comprised between 100°C and 500°C. Moreover, in case of use of different temperatures for preheating the opposite surfaces of the tape of thermoplastic material having cross-section with a hollow profile, the temperature difference is comprised between 1°C and 250°C. The above-mentioned aim is also achieved by an apparatus for carrying out the above method.

According to a preferred embodiment, that apparatus comprises:

- a preheating station for said sheet(s) of thermoplastic material having cross-section with a hollow profile, the preheating station comprising at least one heating device, preferably a pair of opposite heating devices, each comprising at least one heating group, preferably more heating groups composed in turn of at least one heating element, preferably more heating elements operable independently to heat at least one surface, preferably the opposite surfaces of said sheet(s) of thermoplastic material having cross- section with a hollow profile independently at a predetermined temperature,

- at least one processing station for the preheated thermoplastic material having cross-section with a hollow profile exiting from the preheating station, said at least one processing station being selected between the lamination, welding-sealing, thermoforming, creasing, surface treatment, printing, cutting station or combinations thereof,

- means for feeding said sheet(s) thermoplastic material having cross- section with a hollow profile in said preheating station and means for feeding the sheet(s) of preheated thermoplastic material exiting from the preheating station to said at least one processing station. According to an embodiment of the invention, the feeding means to the preheating station comprise a loading station of stacked sheets of said thermoplastic material having cross-section with a hollow profile.

According to another embodiment of the invention, the feeding means to the preheating station comprise at least one reel, preferably a pair of independent reels, on which a tape of sheet of thermoplastic material having cross-section with a hollow profile is wound and means for unwinding said tape of sheet of thermoplastic material having cross-section with a hollow profile from the at least one reel, as well as preferably means for replacing empty reels with full reels during the apparatus operation.

Advantageously, the at least one heating element composing a group of a heating device can comprise a heating element, a system with hole/ holes for letting hot air go out, an irradiator of infrared or UV rays or other heating systems known in the art.

Moreover, advantageously, each heating device can have zones being preheated independently from the heating elements, moreover providing means for adjusting the preheating of such zones in order to preheat mainly (i.e. at a higher temperature) or exclusively zones of said heating device, in particular middle zones of said heating device that in use are facing towards corresponding zones of the thermoplastic material having cross-section with a hollow profile to be prepared, through said preheating, to the next processing in said at least one processing station. It was surprisingly found out that the treatments of thermoplastic materials having cross-section with a hollow profile such as in particular welding- sealing, thermoforming, creasing, cutting or combinations thereof can be effectively carried out both operating at batches on single stacked sheets and operating continuously on a tape of sheet of thermoplastic material obtained from the extrusion die or from a printing apparatus and in case wound in the reel as long as that thermoplastic material is preheated on the surface before those treatments in the modes described by the present invention.

In particular, it was found out that the preheating operated according to the present invention allows the thermoplastic material to be prepared without damaging the hollow inner structure thereof obtained through the extrusion in the above-mentioned next treatments, reducing in particular the deformation and cutting resistance thereof with subsequent significant decrease in welding- sealing and/ or thermoforming and/ or creasing and/ or cutting times as well as a decrease in the wear of welding-sealing and/ or thermoforming and/ or creasing and/ or cutting tools, a decrease in their management costs, an increase in production efficiency and in the final product quality. Moreover, in that way, it is possible to effectively subject to the above-mentioned next treatments also sheets of thermoplastic material having cross-section with a hollow profile with higher basic weights and/or thicknesses, in particular with basic weights from 200 to 3500 g/ m 2 and/ or thicknesses from 2 to 16 mm, which on the contrary are not processable with the above-mentioned prior art methods at batches. Moreover, it must be noted that when feeding a tape of sheet of thermoplastic material having cross-section with a hollow profile with the sheet unwound from a reel, preheating according to the present invention allows the "memory" of the material itself in the winding direction (warp) to be eliminated bringing it in a flatness condition suitable for correctly carrying out the above-indicated next treatments, allowing the continuous processing thereof with subsequent reduction of processing scraps (lower material-grasping margins during cutting), reduction of labour costs to load the material and to supervise the feeding process, and increase in production efficiency. Hence, the introduction of material preheating according to the invention involves the possibility to use a continuous feeding and processing method with the following advantages: a) reduction of processing scraps, b) reduction of labour costs to load the material and to supervise the feeding process, c) increase in production efficiency.

Moreover, the introduction of material preheating according to the invention involves the possibility to reduce the deformation and cutting resistance of the above-mentioned thermoplastic material with a hollow profile with the following advantages: a) reduction of tool wear in the next treatments with subsequent decrease in their management costs, increase in production efficiency and in the final product quality, thereby avoiding any risk of sharp burrs or profiles which are not completely sealed, b) reduction of processing times, c) possibility to process the above-mentioned materials with high densities and thicknesses.

Further features and advantages of the present invention will be apparent from the following description of some preferred embodiments thereof, given by way of non-limiting example with reference to the attached drawings in which:

- figure 1 schematically shows an apparatus according to the present invention for continuously obtaining a plurality of containers in laminated, thermoformed and surface-treated thermoplastic material, with a welded- sealed hollow profile; - figure 2 schematically shows an apparatus according to the present invention for continuously obtaining a plurality of die-cut objects, for example die-cut containers, in laminated and surface-treated thermoplastic material, with a welded-sealed hollow profile, and with the presence of creases along the surface to bend said surface thereof according to the desired shape;

- figure 3 schematically shows an apparatus according to the present invention for continuously printing on portions of a tape of a sheet in thermoplastic material with a hollow profile;

- figure 4 shows an example of sheets of thermoplastic material having cross-section with hollow profile, wherein the hollow profile has an alveolar structure;

- figure 5 shows an example of sheet of thermoplastic material having cross- section with hollow profile, wherein the hollow profile has a bubble guard structure; - figure 6 shows an example of sheet of thermoplastic material having cross- section with hollow profile, wherein the hollow profile has an honeycomb structure.

Detailed description

The term, "sheet of thermoplastic material having cross-section with a hollow profile", means a section bar such as a sheet or a panel having inner cavities or gaps between its upper surface and lower surface according to a predetermined structure or geometry such as an alveolar or cellular geometry with closed and/or open (i.e. communicating between each other) alveoli/ cells. By way of non-limiting examples, the sheet of thermoplastic material can have a hollow inner structure with an alveolar geometry (corrugated, twin wall, hollow profile, etc.) such as the sheets shown in figure 4, a hollow inner structure with a honeycomb structure such as the sheet shown in Figure 6 or a hollow inner structure with air bubble-like (bubbleguard) structure. Those sheets of thermoplastic material are generally obtained through extrusion methods that are traditional per se in different thicknesses, densities or basic weights, colours, shapes etc. according to the intended use or next processing.

With reference to Figure 1 , an apparatus according to the present invention for continuously obtaining a plurality of containers in thermoplastic material having cross-section with a hollow profile is globally indicated with the reference number 1.

The apparatus 1 comprises along the longitudinal handling direction of a tape of thermoplastic sheet having cross-section with a hollow profile, in sequence (from upstream to downstream) a loading and feeding station 2, a preheating station 3, a lamination station 4, a welding- sealing and thermoforming station 5, a surface treatment station 6 and a cutting station 7.

The station 2 comprises a reel 8 on which a tape 10 of sheet of thermoplastic material having cross-section with a hollow profile has been previously wound obtained by extrusion from a die through an extrusion process being traditional per se. By means, in case, of suitable motor means (not shown and traditional per se) which drive the reel 8 in rotation, that tape 10 is unwound from the reel 8 and fed by means of the rollers 1 1 or chain or other equal transport device in the preheating station 3. The preheating station substantially comprises an upper heating device 12 and a lower heating device 13 being opposite to each other at a predetermined distance.

According to the present invention, the tape 10 of thermoplastic material having cross-section with a hollow profile unwound from the reel 8 and transported by the rollers 1 1 longitudinally runs through the preheating station 3 between the upper device 12 and the lower device 13 wherein it is preheated on the surface during the advance at such a temperature as to eliminate a warp of said tape 10 resulting from the previous winding on the reel 8 and to essentially involve a softening in correspondence of the opposite surfaces of the tape 10 without damaging the hollow structure. For this purpose, the upper device 12 and the lower device 13 are equipped with suitable heating elements (not shown), such as for example heating elements or irradiators for example of UV or infrared rays, operated by a suitable energy source. Moreover, the preheating station 2 is preferably equipped with means for independently adjusting the single heating elements of the upper device 12 and of the lower device 13, so as to be able to preheat the opposite surfaces of the curved tape 10 at different temperatures, preferably a higher temperature in correspondence of the convex surface and a lower temperature in correspondence of the concave surface. In the preheating station 3, the tape 10 of thermoplastic material having cross-section with a hollow profile is made essentially flat, having lost in fact the "memory" of the warp in the direction of the previous winding on the reel 8, and it is suitably "prepared" for the next treatments indicated hereafter due to the above-mentioned preheating. In the present embodiment of the invention, the tape 10 exiting from the preheating station 3, suitably transported by the rollers 1 1 , is fed in the lamination station 4 which is optional and can therefore be omitted.

The lamination station 4 comprises a roller press 15 equipped with a pair of opposite and adjacent rollers, driven in rotation in opposite directions to each other, between which the tape 10 of thermoplastic material having cross-section with a hollow profile coming from the preheating station 3 and a tape 16 of other material (for example fabrics, unwoven fabrics, etc.) unwound from a respective feeding reel 17 are brought across.

Through the pression exerted by the rollers of the press 15 and suitable coupling/ welding means (e.g. glues, hot air, etc.), the tape 10 of thermoplastic material having cross-section with a hollow profile and the tape 16 of other material are coupled/ laminated to each other during their advance between the above-mentioned rollers, thereby obtaining a laminated tape 18 comprising a layer of thermoplastic material having cross-section with a hollow profile.

In the present embodiment, that laminated tape 18 coming from the lamination station 4 (or alternatively the tape 10 of thermoplastic material having cross-section with a hollow profile coming from the preheating station 3 if the lamination station 4 is omitted), is fed through the transport by the rollers 1 1 to the welding- sealing and thermoforming station 5 in order to manufacture thermoformed products 20, for example containers, with welded-sealed edges having a predetermined shape.

The welding-sealing and thermoforming station 5 comprises a thermoforming mold having a female half-mold lower portion 21 and a male half-mold upper portion 22 with complementary shapes that are vertically operable (by suitable motor means not shown and traditional per se) between a position in which said half-mold portions are in the position of maximum approach to each other involving the mold closing and a position in which said half-mold portions are in the position of maximum departure from each other, so as to achieve the mold maximum opening position and the extraction of thermoformed products.

To ease thermoforming, the female half-mold lower portion 21 and the male half-mold upper portion 22 are equipped with respective channels 21A and 22A. During the mold closing step, the channels 22A can be crossed by flows of compression air exiting from the male half-mold upper portion 22, and the channels 21A can be crossed by flows of suction air exiting from the female half-mold lower portion 21 , suitably sequenced with each other.

Moreover, the station 5 comprises a welding-sealing unit 23 located above the male half-mold upper portion 22 and equipped with a welding-sealing profile 24 projecting downwards and outwardly from the template/ profile of the male half-mold upper portion 22. Also the welding- sealing unit 23 itself is vertically movable (by suitable motor means not shown and traditional per se) and independently so that the thermoforming step occurs at the end of the welding-sealing. In this regard, the welding-sealing unit 23 can be vertically lowered until the abutment of the welding- sealing profile 24 against the upper plane of the female half-mold 21 , arranging to weld to each other the lower lip with the upper one of the thermoplastic sheet sealing the edges of the product to be thermoformed and trapping the air therewithin in the hollow inner structure of the thermoplastic material, and afterwards the male half-mold upper portion 22 and the female half-mold lower portion 21 are coupled to each other to close the mold to carry out thermoforming. At the end of thermoforming, the mold is opened through the mutual departure of the male half-mold upper portion 22 and of the female half-mold lower portion 21 , moving away at the same time also the welding-sealing unit 23 and obtaining a thermoformed and sealed product which appears to be extracted from the mold and still attached to the laminated tape 18 (or alternatively to the tape 10 of thermoplastic material with a hollow profile).

Advantageously, the above-mentioned welding-sealing and thermoforming operations are carried out continuously and repeatedly along the whole tape of sheet of thermoplastic material having cross-section with a hollow profile (laminated or non-laminated) when it advances towards the thermoforming and welding- sealing station 5, thereby obtaining at the exit of that station a plurality of thermoformed and welded-sealed products still tied to the tape with a reduced longitudinal spacing between adjacent containers and which can be predetermined by synchronizing or suitably adjusting the advance speed of said tape and the handling speed and sequence of the female half- mold lower portion 21 , of the half-mold upper portion 22 and of the overhanging welding- sealing unit 23.

As said above, the welding- sealing of the thermoformed product is particularly advantageous where that container is intended for the packaging, preservation and transport of food such as for example fresh fish, fresh meat, vegetables, fruit and the like. In fact, if the edges of the sheet of thermoplastic material forming the thermoformed product were not sealed, they could trap foreign bodies, dust, liquids, bacteria, mildews and/ or other contaminants within the recesses of the container with the result that the reuse of the container would actually be difficult if not impossible since lacking in hygiene and since it would be extremely difficult and expensive to clean the contaminated recesses so as to bring it back in the hygienic conditions required for reuse. Vice versa, by sealing the edges of the thermoformed product as indicated above, it can be washed/ sanitized or sterilized for uses after the first one in a simpler and cheaper way knowing in fact that there is no contamination within the recesses of the container, making it liquid-leak-proof and thus allowing a transport, a handling and a storage which are always clean and compatible with other goods.

Moreover the welding-sealing of hollow profiles has further particularly remarkable advantages (but not only) in the case of package production such as in particular the fact of having a pliable design so that, once washed, they can be reused several times, considerably reducing purchase costs and transport and vacuum- storage logistic ones, as well as CO2 emissions in the atmosphere due to the lower use of means of transport.

Moreover, the air contained within the profile recesses, with the same thickness used, increases the rigidity of the surfaces (in terms of higher mechanical resistance to compression and flexion, shocks and perforations) allowing to:

- use lower thicknesses and thus save the raw material in the production step, - have a higher load capacity if compared to a package of the same size consisting of the same material and thickness with an unwelded-unsealed hollow profile or if compared to a traditional package of the same size, allowing thus to save load storage and transport costs; this also allows a reduction of CO2 emissions in the atmosphere due to the lower use of means of transport,

- have better heat-insulating properties if compared to a package consisting of the same material and thickness with an unwelded-unsealed hollow profile, and in any case if compared to cardboard packages of equal thickness, when being outside the cold chain. The laminated tape 18 (or alternatively the tape 10 of thermoplastic material with a hollow profile) exiting from the thermoforming and welding-sealing station 5 and carrying the products 20 which are thermoformed and sealed at the edges is transported by the rollers 1 1 to the surface treatment station 6. The station 6 has a unit 25 which is traditional per se, such as for example a sprayer or a coater, capable of applying a liquid or gel material (for example silicone or the like) on a surface of the laminated tape 18 (or of the tape 10 of thermoplastic material with a hollow profile) in order to impart on said surface particular properties (for example antislip properties or properties of absorption of meat and dairy product wheys).

The surface treatment station 6 too is optional and hence it can be omitted. Moreover, the surface treatment step with the above-mentioned station 6 can be alternative to the lamination step with the above-mentioned station 4.

Finally, the surface-treated laminated tape 18 (or alternatively the tape 10 of thermoplastic material having cross-section with a hollow profile) exiting from the above-mentioned surface treatment station 6 is transported by the rollers 1 1 to the cutting station 7.

The cutting station 7 has a cutter having an upper part 26 and a lower part 27 both equipped with cutting ends 28 being vertically movable in approaching sequences against the laminated tape 18 or the tape 10 so as to sequentially separate the thermoformed products 20 from their processing scrap and subsequent departure from said laminated tape 18 or the tape 10 after each cutting and separation of a thermoformed product 20. The above-mentioned approaching movement and subsequent departure of the upper part 26 and of the lower part 27 of the cutter is sequential and suitably synchronized with the correct positioning of each thermoformed product 20 to be separated in the cutting station 7 determined by the advance of the above-mentioned laminated tape 18 or tape 10 and by the predetermined spacing between consecutive thermoformed products 20. Advantageously for low densities (approximately up to 600 g/mm2) and low thicknesses (approximately up to 4 mm) the above-mentioned cutting step can be integrated in the welding- sealing and thermoforming station 5 obtaining a considerable saving on apparatus manufacturing costs.

Figure 2 schematically shows an apparatus according to the present invention for continuously obtaining a plurality of die-cut objects for example die-cut containers in laminated and surface-treated thermoplastic material, with a welded-sealed hollow profile, and with the presence of creases along the surface to ease the bending thereof, which apparatus is globally indicated with the reference number 30. Figure 3 schematically shows instead an apparatus according to the present invention for continuously printing on portions of a tape of a sheet in thermoplastic material having cross-section with a hollow profile, which apparatus is globally indicated with the reference number 40. The elements of apparatuses 30 and 40 respectively shown in Figure 2 and in Figure 3 that appear to be structurally and/ or functionally equal to corresponding elements of the above-described apparatus 1 of Figure 1 , will be assigned the same reference numbers of the latter ones and will not be further described for the sake of brevity. With reference to Figure 2, the apparatus 30 differs from the above- described apparatus 1 for the fact that the thermoforming and welding- sealing station 5 of the apparatus 1 is replaced by a welding- sealing and creasing station 31 , wherein the term creasing means a buckling and/ or yielding operation of the thermoplastic material, of any profile hot- performed on one or more parts of the surface to ease the bending thereof avoiding possible deformations thereof.

The welding-sealing and creasing station 31 comprises a welding-sealing upper unit 33 equipped with an outer welding-sealing profile 24 and a creasing profile 34, both projecting downwards, and a lower block 32, vertically movable in approaching sequences against the laminated tape 18 (or the tape 10 if lamination in station 4 is omitted) so as to weld-seal and crease consecutive portions of the laminated tape 18 (or of the tape 10) according to profiles defining plane templates (i.e. die-cut objects) of respective containers (or of products in general) and subsequent departure from said laminated tape 18 (or said tape 10) after each welding-sealing and creasing sequence which defines the above-mentioned die-cut object. The above-mentioned approaching movement and subsequent departure of the welding-sealing/ creasing upper unit 33 and of the lower block 32 is hence sequential and suitably synchronized with the advance of the above- mentioned laminated tape 18 (or of the tape 10) and the predetermined spacing between consecutive die-cut containers.

Therefore, after the optional surface treatment in the station 6, the laminated tape 18 (or the non-laminated tape 10) is fed to the cutting station 7 which, by operating as already illustrated above, arranges in any case to sequentially separate die-cut objects from their processing scraps. Also in this embodiment of the apparatus, advantageously for low densities (approximately up to 600 g/mm 2 ) and low thicknesses (approximately up to 4 mm) the above-mentioned cutting step can be integrated in the welding- sealing and creasing station 31 obtaining a significant saving on apparatus manufacturing costs.

In an alternative embodiment of the apparatus 30 of Figure 2, the welding- sealing and creasing station 31 can comprise a roller equipped with welding-sealing and creasing molds, wherein said molds are consisting of raised profiles realized on curved surfaces that are fastened on the above- mentioned roller, rather than the above-mentioned vertically-movable welding- sealing and creasing upper unit 33, the lower support plane (block 32) still existing. This solution is particularly indicated where materials with a large hollow profile must be processed such as for example in the case of boating applications, like boats, kayaks, platforms etc. while on the contrary a vertically-movable welding- sealing and creasing solution like the upper unit 33 depicted in figure 2 would be difficult and expensive to implement for these applications because of the relevant masses at stake to be handled. With reference now to Figure 3, a printing process carried out upstream of the processes of Fig. 1 or Fig. 2 and not in line with the above-mentioned processes is illustrated. The apparatus in the most general embodiment thereof comprises along the longitudinal handling direction of a tape of thermoplastic sheet having cross-section with a hollow profile, in sequence (from upstream to downstream) a feeding station 2, a first heating station 3a, a printing station 41 , a second heating station 3b and a rewinding station 42.

The first heating station 3a and the second heating station 3b are structurally and/ or functionally equal to each other and they are as well structurally and/ or functionally equal to the preheating station 3 of the above-described apparatus 1.

Similarly to the above-described apparatus 1 , in the apparatus 40 the tape 10 of thermoplastic material having cross-section with a hollow profile is unwound from the reel 8 and preheated in the first preheating station 3a to eliminate the warp and arrange it for the next treatments.

At this point, the preheated tape 10 is fed by the rollers 1 1 to the printing station 41 (carried out with any technique) wherein predefined printing patterns like for example wordings, crests, trademarks, decorations and/or any graphic composition required for example by the producer and/ or by the user according to tastes and specific needs are imparted on one or both the surfaces thereof in succession. The spacing between consecutive printing patterns can be suitably adjusted, for example suitably adjusting the advance speed of the tape 10 as a function of the times for creating the printing pattern by means of the apparatus 41.

The printed tape 10 exiting from the printing station 41 is then sent by means of the rollers 1 1 in the second heating station 3b and therefrom to the station 42 wherein it is rewound on a reel 43.

Advantageously, the heating of the printed tape 10 in the second station 3b is carried out at a temperature that helps the rewinding on the reel, for example a temperature between 50°C and 500°C. Moreover, in case of use of different temperatures for heating the opposite surfaces of the tape of thermoplastic material with a hollow profile, the temperature difference is comprised between 1°C and 250°C. Advantageously, the printed tape 10 wound on the reel 43 can be then subjected to next treatments, in particular with the apparatus 1 of Figure 1 or with the apparatus 30 of Figure 2, in order to obtain thermoformed products or general die-cut creased ones, with a welded-sealed hollow profile, each carrying the desired printing pattern respectively. In that case, the rewound reel 43 of the apparatus 40 constitutes the feeding reel 8 of the apparatus 1 of Figure 1 or of the apparatus 30 of Figure 2.

Alternatively, in an alternative embodiment of the present invention, the second heating station 3b and the rewinding station 42 can be omitted and the apparatus 40 can be thus integrated in line with the apparatus 1 of Figure 1 or the apparatus 30 of Figure 2 upstream of the preheating station 3 of said apparatus 1 or of said apparatus 30 omitting at the same time also the feeding station 2 and the preheating station 3 of said apparatus 1 or of said apparatus 30. In that way, the printed tape 10 exiting from the printing station 41 can be directly subjected, without rewinding on the reel, to the next operations, like those provided in the apparatus 1 or in the apparatus 30.

In another alternative embodiment of the present invention, the printing step could be carried out downstream of the apparatus 1 of Figure 1 or of the apparatus 30 of Figure 2, being thereby able to receive only die-cut material in flat or thermoformed sheets and omitting therefore the feeding station 2, the rewinding station 42 and the heating stations 3a and 3b.

Moreover and alternatively the printing step could be integrated as a processing station in the apparatus 1 of figure 1 , preferably between the thermoforming + welding- sealing station and the surface treatment station, or in the apparatus 30 of figure 2, preferably between the welding-sealing and creasing station and the surface treatment station.

A person skilled in the art could bring several modifications or alternatives to the above-described method and apparatus, all however comprised within the scope of protection of the following claims. In this regard, it must be noted in particular that the present invention is not limited to the above- illustrated embodiments, but also apparatuses comprising one or more of any above-illustrated processing station or also other processing stations of thermoplastic materials having cross-section with a hollow profile fall within the scope of the invention, in any order, as long as the one or more processing stations is/ are preceded by the preheating of the thermoplastic material having cross-section with a hollow profile according to the modes described by the present invention.




 
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