Method and machine for removing printed film from hollow bodies

Abstract

A method for removing sublimation printed film from a hollow body, in particular a bottle, comprising the steps of: a film (2) of thermoplastic material adhered to a hollow body (3) so as to form a network of microchannels; bringing the film (2) to a certain temperature so as to bring the film (2) into a plastic phase; supplying a pressurized fluid at a certain pressure to the network of microchannels when the film (2) is in the plastic phase so as to at least partially detach the film (2) from the hollow body (3); bringing the film (2) to a certain temperature so as to bring the film (2) into a glassy phase; and removing the film (2) when the film is in the glassy phase.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This patent application claims priority from Italian Patent Application No. 102023000003039, filed February 22, 2023, the entire disclosure of which is incorporated herein by reference.

[0002] The present invention relates to a method for removing printed films from hollow objects, and in particular to a method for printing on the exterior surfaces of hollow containers such as bottles, vials, and jars made from glass, ceramic, or similar materials. [Background technology]

[0003] Specific equipment and processes are known for producing decorations via thermal transfer using inks, in particular via dye sublimation printing.

[0004] In this field, there is an increasing demand for greater attention to the qualitative aspects of dye-sublimation printing, such as, for example, the sharpness of the graphics and the precision with which the decoration or lettering is applied to specific reference points on the hollow body.

[0005] In particular, U.S. Patent No. 5,929,663 teaches how to apply decorations to hollow glass objects such as bottles or vials using a dye-sublimation printing process with a high level of quality in terms of clarity of the decoration and accuracy of application. The process described in this patent involves creating a sleeve with an uneven inner surface, made from a sheet of film, usually a thermoplastic material such as PET or PETG, rolled into a cylinder, and welded at the edges with an adhesive or solvent from the polymer itself using a tubing machine, with a graphic design along its uneven inner surface. The graphic design is applied directly to the film with ink that is intended to be transferred to the hollow object to be decorated.

[0006] The process involves placing a sleeve around a hollow body, applying heat to the sleeve to cause heat shrinkage and adhesion of the sleeve to the hollow body, applying heat at ink sublimation temperatures to the sleeve and hollow body to sublimate the ink particles, and transferring the graphic design to the hollow body while simultaneously extracting excess gas generated during sublimation through a network of microchannels extending between the heat-shrunk sleeve and the hollow body. The microchannels between the hollow body and the heat-shrunk sleeve are formed because the sleeve has a roughened inner surface designed to form the microchannels after being heat-shrunk into a film and adhered to the hollow body.

[0007] Although the process described in US Patent No. 5,949,663 appears to be particularly satisfactory in terms of quality, one of the problems faced in sublimation printing is combining a high quality level with an efficient industrialization of the production process in order to reduce production costs. A drawback faced in the known process is the removal of the film once the transfer of the sublimation ink is complete. In particular, the most complex and time-consuming step in removing the film is to separate it from the hollow body without damaging the hollow body and the decoration. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] International Publication No. 2021 / 260613A1 Brochure Summary of the Invention [Problem to be solved by the invention]

[0009] One object of the present invention is to provide a method for use in hollow body printing processes, in particular for printing on the exterior surfaces of hollow bodies such as bottles, vials and jars, which method does not have the drawbacks of the prior art. [Means for solving the problem]

[0010] According to the invention, there is provided a method for removing a printed film from a hollow body, in particular from a bottle, in particular, but not necessarily, for removing a sublimation printed film, the film adhering to the hollow body so as to form a network of microchannels, - subjecting the film to a temperature so as to cause the film to enter a plastic phase; - supplying a pressurized fluid at a pressure to the network of microchannels when the film is in a plastic phase so as to at least partially pull the film away from the hollow body; - subjecting the film to a temperature so as to bring the film, once detached from the hollow body, into a glassy phase; removing the film when the film is in the glassy phase; A method is provided which includes:

[0011] Once the film is in its glassy state, its elastic return is very limited and practically negligible, so that it no longer adheres to the hollow body and its removal becomes much easier and can be done without causing damage to the hollow body and the decoration. In fact, removing the film can involve tearing the film and cutting the part that has been torn off to initiate the tearing. This operation can be easily performed using a laser beam tuned to focus on the film.

[0012] Alternatively, rupturing the film involves supplying a pressurized fluid between the hollow body and the film when the film is in the glassy phase at a predetermined pressure, for example between 2 bar and 10 bar, for a period of several seconds to rupture the film.

[0013] In particular, the method includes using a fitting in communication with a pressurized fluid source to supply pressurized fluid to the opening, in effect the fitting allows pressurized fluid to be supplied between the film and the hollow body.

[0014] For this purpose, the fitting is wrapped with a film together with the hollow body to form an assembly, and is provided with a pressurized fluid supply and a passage communicating with said microchannel.

[0015] In particular, the method includes the step of clamping the assembly before supplying pressurized fluid between the pocket and the thrust reverser device to prevent the pressurized fluid from pushing the assembly out of the pocket.

[0016] The method includes providing pressurized fluid within the hollow body to define a pressurized fluid reservoir for compensating for leakage.

[0017] In particular, the method includes advancing the hollow body by means of a conveyor simultaneously with the supply of pressurized fluid, in this way it is possible to create a dynamic machine in which pressurized fluid can be supplied to the micro-passages during the advancement of the conveyor.

[0018] A further object of the present invention is to provide a machine for removing sublimation printed films from hollow bodies, in particular from bottles, which does not have the drawbacks of the prior art.

[0019] According to the invention, a machine for removing sublimation printed films from hollow bodies, in particular from bottles, is provided, which machine comprises: a heater for heating the film to a temperature such that the film is in a plastic phase; a blower for supplying a pressurized fluid at a pressure to the microchannels so as to at least partially pull the film away from the hollow body when the film is in a plastic phase; - a cooling system that allows the film to reach a glass phase after being separated from the hollow body; A machine comprising:

[0020] Further features and advantages of the present invention will become apparent from the following description of non-limiting embodiments of the invention, with reference to the figures of the accompanying drawings. [Brief explanation of the drawings]

[0021] [Figure 1]1 is a side elevational and longitudinal cross-sectional view of a machine made in accordance with the present invention, with parts removed for clarity; FIG. [Figure 2] FIG. 2 is a side elevational view of a detail of the machine in FIG. 1, with parts removed for clarity. [Figure 3] FIG. 2 is a side elevational view of a detail of the machine in FIG. 1, with parts removed for clarity. [Figure 4] FIG. 2 is a side elevational view of a detail of the machine in FIG. 1, with parts removed for clarity. [Figure 5] FIG. 2 is a side elevational view of a variation of the machine in FIG. 1, with parts removed for clarity. DETAILED DESCRIPTION OF THE INVENTION

[0022] In FIG. 1 , the numeral 1 generally designates a machine for removing a sublimation printing film 2 from a hollow body 3, in particular for printing on the exterior surfaces of containers such as bottles, vials, and jars made from glass, ceramic, or similar materials. The machine 1 is associated with or is a station in a sublimation printing plant, not shown in the accompanying drawings. The machine 1 includes a conveyor 4 for advancing an assembly 5 formed by the hollow body 3, a fitting 6, and the film 2 adhering to the hollow body 3 and the fitting 6 along a predetermined path P. The surfaces of the film in contact with the hollow body 3 and the fitting 6 are rough or uneven so as to form a dense network of microchannels or thin tunnels throughout the entire length of the film 2. Alternatively, the inner surface of the film can be smooth, and the outer surfaces of the hollow body 3 and the fitting are roughened to similarly create a dense network of microchannels.

[0023] In the case shown here, the hollow body 3 is a bottle, comprising an opening 7 , a bottom 8 opposite the opening 7 , and a cylindrical side wall 9 which converges in the area near the opening 7 .

[0024] The conveyor 4 comprises pockets 10 for supporting the assemblies 5, and the hollow bodies 3 are arranged with their openings 7 facing the pockets 10. In other words, the bottles are transported upside down. In the case shown here, a support device 11 is arranged between the assemblies 5 and the pockets 10, the support device 11 being partially housed in the pockets 10 so that it can rotate about the axis A thereof.

[0025] The fitting 6 is partly housed in the hollow body 3 and partly housed in the support device 11 and is wrapped with the film 2 at least along its sides.

[0026] The support device 11 comprises a resilient element 12 , in this case an O-ring, to sandwich the film 2 into the fitting 6 , closing the microchannel and minimizing fluid leakage between the film 2 and the fitting 6 .

[0027] The fitting 6 and hollow body 3 are in contact with each other but are configured to allow the passage of fluid both through the network of micro-channels between the film 2 and hollow body 3 and within the hollow body 3.

[0028] The support device 11 comprises an externally toothed ring gear 13 configured to mesh with a fixed gear not shown in the accompanying figures and to rotate the support device 11 together with the assembly 5 during advancement of the conveyor 4.

[0029] The conveyor 4, fittings 6, pockets 10, and support devices 11 together define a passageway 14. The machine 1 includes a manifold 15 extending along the path of the conveyor 4, and a blower 16 for supplying pressurized air along the manifold 15, the passageway 14, the micropassages, and the interior of the hollow body 3.

[0030] The machine 1 further comprises a heater 17 configured to bring the temperature of the film 2 to the plastic phase. The plastic phase for the materials used for the film 2 is reached at a membrane temperature between 80° C. and 120° C. The materials used are in particular PET, PETG, PVC, PE or PP, whether or not combined with one another.

[0031] In particular, film 2 is made from anisotropic heat shrinkable PET and PETG, a layered material with a base layer of single melt shrinkable PET and PETG.

[0032] According to a variant, not shown, the support device 11 is omitted and the pocket 10 is configured to directly receive the fitting 6 and to sandwich the film 2 therein.

[0033] Referring to Figure 2, the machine 1 is provided with a thrust reverser device 18 selectively movable between a raised position (not shown in the accompanying figures) and a lowered position for sandwiching the assembly 5 between the thrust reverser device 18 and the pocket 10.

[0034] The machine 1 further comprises a cooling system 19 for circulating cold air to bring the film 2 to a glass phase below 80° C. The glass phase is reached below 80° C. for the following materials used in the production of the film 2: PET, PETG, PVC, PE, and PP.

[0035] 3, the machine 1 includes a cutting tool 20 to cut the film 2 and initiate a tear in the film. The cutting tool 20 includes a mechanical tool and a laser emitter.

[0036] In use, the conveyor 4 advances the assembly 5 along a predetermined path during which the film 2 is brought to a temperature in the range of 80°C to 120°C to maintain the film 2 in the plastic phase once the temperature reaches the plastic phase. The heater 17 is used, if necessary, when the film is at a temperature below 80°C. Meanwhile, the thrust reverser 18 is lowered until the assembly 5 is sandwiched between the thrust reverser 18 and the pocket 10.

[0037] A blower 16 then supplies a pressurized fluid, such as air, into the network of micro-passages, in particular at a pressure between 0.5 bar and 2 bar, in order to pull the film 2 away from the hollow body 3 .

[0038] Cooling system 19 then reduces the temperature of film 2 until it is in a glassy state, specifically below 80° C. Film 2 in its glassy state is cut by cutting tool 20 to begin breaking film 2 to facilitate its removal.

[0039] Referring to FIG. 4, according to a variant of the invention, the cutting tool is omitted and a blower increases the pressure in the microchannels to a value between 2 bar and 10 bar when the film 2 is in the glassy phase until the film 2 breaks by rupture.

[0040] In FIG. 4 , the thrust reverser device 18 is equipped with a remotely controlled gripper 21 for selectively gripping the free end of the film 2 at the bottom 8 of the hollow body 3 and removing at least a portion of the film 2 from the hollow body 3.

[0041] The remaining portions of film 2 are removed by other means, leaving hollow body 3 completely free of film 2, as shown in FIG.

[0042] The hollow body 3 can then be removed from the pocket 10 .

[0043] According to an alternative not shown in the accompanying figures, removal of the film does not involve breaking the film but is based on its expansion and consequent detachment from the hollow body in the plastic phase, and subsequent reduction in temperature to the glassy phase, following which the film remains detached from the hollow body and for this reason can be easily removed. [Example]

[0044] By way of purely illustrative example, experimental testing was conducted on a film 2 made from a layered material with an anisotropic, heat-shrinkable PET or PETG substrate, i.e., a PET or PETG substrate that is heat-shrinkable in only one direction; further testing was conducted on PET, PETG, PVC, PE, or PP films, even when combined with one another. A sleeve was created from the layered material printed with a graphic design using sublimation ink. The sleeve was then fitted around a hollow body and heated to a temperature that heat-shrunk the sleeve around the hollow body to form a film that adheres to the hollow body and a network of microchannels. Heat was applied to the ink sublimation temperature to transfer the graphic design to the hollow body, while excess gas produced during sublimation was simultaneously extracted through the network of microchannels.

[0045] Next, the film 2 is brought to a temperature between 80°C and 120°C or maintained in a plastic phase at a temperature between 80°C and 120°C, then a pressurized fluid (e.g., air) is supplied to the microchannels for several seconds at a pressure between 0.5 bar and 2 bar to cause at least partial detachment of the film 2 in the plastic phase from the hollow body 3, the film 2 detached from the hollow body 3 is then brought to a glassy phase to a temperature below 80°C, and finally the film 2 in the glassy phase is removed.

[0046] The film 2 behaves like glass below the glass transition temperature Tg, which for the materials used is less than 80°C, and like plastic in the temperature range between the glass transition temperature Tg and the melting temperature Tf, which for the materials used is greater than 120°C, typically greater than 200°C.

[0047] Finally, it is evident that the present invention covers further variations to the embodiments described herein, which variations fall within the scope of protection of the appended claims. [Explanation of symbols]

[0048] 1 machine 2. Sublimation printing film 3 Hollow body 4 Conveyor 5 Assembly 6. Fitting 7 aperture 8 bottom 9 side wall 10 pockets 12 Elastic Elements 13 Externally toothed ring gear 14 Passage 16 Blower 17 Heater 18 Thrust Reverse Device 19 Cooling System 20 cutting tools 21 Remote control gripper A-axis P Predetermined route

Claims

1. 1. A method for removing a printed film from a hollow body, in particular from a bottle, in which said film (2) of thermoplastic material, in particular with a base layer of semicrystalline polymer, in particular of PET or PETG, is adhered to the hollow body (3) following heat shrinkage so as to form a network of microchannels, Bringing the film (2) to a temperature, in particular between 80°C and 120°C, so as to bring the film (2) into a plastic phase or to maintain the film (2) in the plastic phase; supplying a pressurized fluid to the microchannels, in particular at a pressure between 0.5 bar and 2 bar, so as to at least partially separate the film (2) from the hollow body (3) when the film (2) is in the plastic phase; bringing the film (2) detached from the hollow body (3) to a temperature, in particular below 80°C, so as to bring the film (2) into a glassy phase; removing the film (2) when the film (2) is in a glass phase; A method comprising:

2. 10. The method of claim 1, wherein the step of removing the film (2) includes cutting the torn portion of the film (2) to initiate tearing of the film (2).

3. 3. The method of claim 2, comprising cutting the film (2) using a laser beam.

4. 2. The method according to claim 1, wherein the step of removing the film (2) comprises supplying a pressurized fluid between the hollow body (3) and the film (2) when the film (2) is in a glassy phase, in particular at a pressure between 2 bar and 10 bar, so as to rupture the film (2).

5. 2. The method of claim 1, wherein the hollow body (3) comprises an opening (7), the method comprising the step of supplying the pressurized fluid at the opening (7) using a fitting (6) in communication with a pressurized fluid source.

6. 6. The method of claim 5, wherein the fitting (6) is wrapped with the film (2) together with the hollow body (3) to form an assembly (5), and includes a passage (14) in communication with the pressurized fluid supply source and the microchannel.

7. 7. The method of claim 6, including clamping the assembly (5) before supplying the pressurized fluid between the pocket (10) and the thrust reverser device (18).

8. 2. The method of claim 1, comprising supplying the pressurized fluid into the hollow body (3).

9. 2. The method of claim 1, further comprising advancing the hollow body by means of a conveyor (4) simultaneously with the supply of pressurized fluid.

10. 10. The method of claim 9, including the step of supplying pressurized fluid to the micropassages during advancement of the conveyor (4).

11. A printing film removing machine (1) for removing a printing film from a hollow body (3), in particular from a bottle, for carrying out the method according to claim 1, comprising: a blower (16) for supplying a pressurized fluid at a pressure to the microchannels so as to at least partially separate the film (2) from the hollow body (3) when the film (2) is in a plastic phase; a cooling system (19) for allowing the film (2) separated from the hollow body to reach the glass phase; Equipped with a printing film removal machine.

12. 12. The machine according to claim 11, comprising a conveyor (4) for advancing the hollow bodies (3) and each of the films (2) along a predetermined path (P).

13. 12. The machine according to claim 11, comprising a cutting tool (20) for making a cut in the film and initiating a tear in the film (2), in particular the cutting tool (20) being a laser emitter.

14. 12. The machine of claim 11, comprising a fitting (6) and a manifold (15) for connecting the hollow body (3) to the blower (16).

15. 15. A machine as claimed in claim 14, comprising a thrust reverser (18) for clamping the hollow body (3) between the conveyor (4) and the thrust reverser (18).

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