Method and machine for removing a printing film from a hollow body

Abstract

A method for removing a sublimation printing film from a hollow body, in particular from a bottle, wherein the film (2) in thermoplastic material adheres to a hollow body (3) so as to form a network of micro-channels comprises: - bringing the film (2) to a temperature such as to place the film (2) into the plastic phase; - supplying a pressurized fluid to the network of micro-channels at a pressure such as to detach, at least partly, the film (2) from the hollow body (3) when the film (2) is in the plastic phase; - bringing the film (2) to a temperature such as to place the film (2) into the glass phase; and - removing the film (2) when the film is in the glass phase.

Description

[0001] "METHOD AND MACHINE FOR REMOVING A PRINTING FILM FROM A

[0002] HOLLOW BODY"

[0003] CROSS-REFERENCE TO RELATED APPLICATIONS

[0004] This Patent Appl ication claims priority from Italian Patent Application No . 102023000003039 filed on February 22 , 2023 , the entire disclosure of which is incorporated herein by reference .

[0005] TECHNICAL FIELD

[0006] The present invention relates to a method for removing a printing film from a hollow body, in particular for printing external surfaces of hollow containers such as bottles , vials , and j ars made of glass , ceramic or similar materials .

[0007] STATE OF THE ART

[0008] Speci fic equipment and processes are known for creating decorations via hot trans fer using inks , in particular via sublimation printing .

[0009] In this sector there is a growing demand for greater attention to the qualitative aspects of sublimation printing, such as , for example , the definition of the graphics and the accuracy of af fixing decorations or writing to speci fic reference points of the hollow body .

[0010] In particular, document WO 2021 / 260613 Al teaches how to af fix decorations to hollow glass bodies and the like , such as bottles or vials , by means of a sublimation printing process with high quality levels in terms of the de finition of the decorations and the af fixing accuracy thereof . The process described in this patent involves creating a sleeve , which has an uneven inner face , made from a sheet o f film in thermoplastic material , usually PET or PETG, wrapped into a cylinder and welded on the edges with adhesive or solvent from the polymer itsel f by means of a tubing machine and bearing a graphic design along its uneven inner face . The graphic design is made directly on the film with an ink which is intended to be trans ferred onto the hollow body to be decorated .

[0011] The process involves arranging the sleeve around the hollow body, applying heat to the sleeve to cause its thermoretraction and adhesion to the hollow body, applying heat at an ink sublimation temperature to the sleeve and hollow body to sublimate the ink particles and trans ferring the graphic design onto the hollow body and simultaneously extracting the excess gas produced during the sublimation through a network of micro-channels extending between the thermoretracted sleeve and the hollow body . The microchannels between the hollow body and the thermoretracted sleeve are formed due to the fact that the sleeve has a rough inner face designed to form the micro-channels once the sleeve has been thermoretracted into a film adhering to the hollow body .

[0012] The process described in WO 2021 / 260613 Al appears to be particularly satis factory in terms of quality, however, one of the problems encountered in sublimation printing is to combine a high quality level with an ef ficient industriali zation of the production process in order to reduce production costs . A drawback encountered in known processes is the removal of the film once the trans fer of the sublimation inks has been completed . In particular, the most complex and time-consuming step in removing the film is detaching the film from the hollow body without damaging the hollow body and the decoration . OBJECT OF THE INVENTION

[0013] One obj ect of the present invention is to provide a method to be used in a hollow body printing process , in particular for printing external surfaces of hollow bodies , such as bottles , vials , and j ars , which is free from the drawbacks of the prior art .

[0014] In accordance with the present invention, a method is provided for removing a printing film, in particular but not necessarily a sublimation printing film, from a hollow body, in particular from a bottle , wherein the film adheres to a hollow body so as to form a network of micro-channels , the method comprising :

[0015] - bringing the film a to a temperature such as to place the film into the plastic phase ;

[0016] - supplying a pressuri zed fluid to the network of microchannels at a pressure such as to detach, at least partly, the film from the hollow body when the film is in the plastic phase ;

[0017] - bringing the film to a temperature such as to place the film detached from the hollow body into the glass phase ; and

[0018] - removing the film when the film is in the glass phase .

[0019] Once the film is in the glassy state , the elastic return of the film is very limited and practically negligible , so the film no longer adheres to the hollow body and its removal is much easier and takes place without causing damage to the hollow body and the decoration . In fact , the removal of the film may involve tearing the film and cutting the detached part of the film in order to start tearing the film . This operation can be easily carried out using a laser beam calibrated to focus on the film .

[0020] Alternatively, tearing the film involves supplying pressuri zed fluid for periods of a few seconds at a predetermined pressure , for example between 2 and 10 bar, between the hollow body and the fi lm when the film is in the glass phase so as to cause the film to burst .

[0021] In particular, the method comprises using a fitting communicating with a pressuri zed f luid source to supply the pressuri zed fluid at said opening . In practice , the fitting allows the pressuri zed fluid to be supplied between the film and the hollow body .

[0022] For this purpose , the fitting is wrapped in the film together with the hollow body to form an assembly and comprises a channel communicating with the pressuri zed fluid source and with said micro-channels .

[0023] In particular, the method comprises clamping the assembly before supplying the pressuri zed fluid between a pocket and a counter-thrust device in order to prevent the pressuri zed fluid from pushing the assembly out of the pocket .

[0024] The method comprises supplying the pressuri zed f luid inside the hollow body in order to define a pressuri zed fluid reserve to compensate for any leakage .

[0025] In particular, the method comprises advancing the hollow body by means of a conveyor simultaneously with the supply of a pressuri zed fluid . In this way, it is possible to create a dynamic machine which is capable of supplying pressuri zed fluid to the micro-channels during the advance of the conveyor .

[0026] A further obj ect of the present invention is to provide a machine for removing a sublimation printing film from a hollow body, in particular from a bottle , which is free from the drawbacks of the prior art . In accordance with the present invention, a machine is provided for removing a sublimation printing film from a hollow body, in particular from a bottle , comprising

[0027] - heaters for heating the film to such a temperature that the film is in the plastic phase ,

[0028] - a blower for supplying a pressuri zed fluid to the micro-channels at a pressure such as to detach at least partly the film from the hollow body when the film is in the plastic phase ; and

[0029] - a cooling system such that the film detached from the hollow body is in the glass phase .

[0030] BRIEF DESCRIPTION OF THE FIGURES

[0031] Further features and advantages of the present invention will be apparent from the following description of non-limiting embodiments thereof , with reference to the Figures of the attached drawings , wherein :

[0032] - Figure 1 is a side elevation and longitudinal section view, with parts removed for clarity, of a machine made in accordance with the present invention;

[0033] - Figures 2 to 4 are side elevation views , with parts removed for clarity, of a detail of the machine in Figure 1 ; and

[0034] - Figure 5 is a side elevation view, with parts removed for clarity, of a variant of the machine in Figure 1 . PREFERRED EMBODIMENT OF THE INVENTION In Figure 1 , reference number 1 indicates , as a whole , a machine for removing a sublimation printing film 2 from a hollow body 3 , in particular for printing external surfaces of containers , such as bottles , vials , and j ars made of glass , ceramic or similar materials . The machine 1 is associated with or is a station of a sublimation printing plant , not shown in the attached figures . The machine 1 comprises a conveyor 4 to advance , along a predetermined path P, an assembly 5 formed by the hollow body 3 , a fitting 6 , and the film 2 that adheres to the hollow body 3 and the fitting 6 . The face of the film in contact with the hollow body 3 and the fitting 6 is rough or uneven so as to form a dense network of micro-channels or narrow tunnels throughout the entire length of the film 2 . Alternatively, the inner face of the film i s smooth whereas the outer face of the hollow body 3 and the fitting are rough to similarly make the dense network of micro-channels .

[0035] In the case illustrated herein, the hollow body 3 is a bottle and comprises an opening 7 ; a bottom 8 opposite the opening 7 ; and a cylindrical side wall 9 converging in the section near the opening 7 .

[0036] The conveyor 4 comprises a pocket 10 to support the assembly 5 , wherein the hollow body 3 is arranged with the opening 7 facing the pocket 10 . In other words , the bottle is carried upside down . In the case illustrated herein, a support device 11 is arranged between the assembly 5 and the pocket 10 , the support device 11 being partially housed so that it can rotate around an axis Al within the pocket 10 .

[0037] The fitting 6 is housed partly in the hollow body 3 and partly in the support device 11 and is wrapped in the film 2 at least along its side face .

[0038] The support device 11 comprises an elastic element 12 , in this case an 0-ring, to clamp the film 2 against the fitting 6 and close the micro-channels and minimi ze the fluid leakage between the film 2 and the fitting 6 .

[0039] The fitting 6 and the hollow body 3 are in contact with each other but are configured to allow the passage of fluids both in the network of micro-channels between the film 2 and the hollow body 3 and within the hollow body 3 .

[0040] The support device 11 comprises an external ring gear 13 configured to mesh with a fixed gear, not shown in the attached figures , and rotate the support device 11 with the assembly 5 during the advance of the conveyor 4 .

[0041] The conveyor 4 , the fitting 6, the pocket 10 , and the support device 11 together define a channel 14 . The machine 1 comprises a mani fold 15 extending along the path of the conveyor 4 ; and a blower 16 to supply pressuri zed air along the mani fold 15 , the channel 14 , the micro-channels , and inside the hollow body 3 .

[0042] The machine 1 further comprises heaters 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 temperature of the film between 80°C and 120°C. The materials used are, in particular, PET, PETG, PVC, PE or PP, whether or not combined with each other.

[0043] In particular, the film 2 is made of a layered material with a base layer of anisotropic thermoretractable PET and PETG, i.e., retractable in a single solution.

[0044] In accordance with a variant, not shown, the support device 11 is omitted and the pocket 10 is configured to directly house the fitting 6 and clamp the film 2 onto the fitting 6.

[0045] With reference to Figure 2, the machine 1 comprises a counter-thrust device 18 selectively movable between a raised position (not shown in the attached Figures) and a lowered position in order to clamp the assembly 5 between the counter-thrust device 18 and the pocket 10.

[0046] The machine 1 further comprises a cooling system 19 circulating cold air to bring the film 2 below 80°C and into the glass phase. The glass phase is reached below 80°C for the following materials PET, PETG, PVC, PE and PP used in the production of the film 2.

[0047] With reference to Figure 3, the machine 1 comprises a cutting tool 20 to cut the film 2 and start tearing the same. The cutting tool 20 includes mechanical tools and laser emitters .

[0048] In use , the conveyor 4 advances the assembly 5 along a predetermined path along 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 has reached the plastic phase . Heaters 17 shall be used, i f necessary, i f the film is at a temperature below 80 ° C . Meanwhile , the counter-thrust device 18 is lowered until the assembly 5 is clamped between the counter-thrust device 18 and the pocket 10 .

[0049] Subsequently, the blower 16 supplies a pressuri zed fluid, for example air, particularly at a pressure between 0 . 5 and 2 bar, to the network of micro-channels to detach the film 2 from the hollow body 3 .

[0050] The cooling system 19 then lowers the temperature of the film 2 unti l the film 2 is in the glassy state , in particular below 80 ° C . The film 2 in the glassy state is cut by the cutting tool 20 in order to start tearing the film 2 to facilitate its removal .

[0051] With reference to Figure 4 in accordance with a variant of the present invention, the cutting tool is omitted and the blower increases the pressure in the micro-channels to values between 2 and 10 bar when the film 2 is in the glass phase , until the film 2 tears by bursting .

[0052] In Figure 4 , the counter-thrust device 18 is equipped with a remotely controlled gripper 21 to selectively grasp the free end of the film 2 at the bottom 8 of the hollow body 3 and remove at least part of the film 2 from the hollow body 3 .

[0053] The remaining part of the film 2 is removed by other means and the hollow body 3 is completely devoid of it , as shown in Figure 5 .

[0054] Subsequently, the hollow body 3 can be removed from the pocket 10 .

[0055] According to an alternative not shown in the attached Figures , the removal of the film does not involve tearing it and is based on the fact that , following the inflation of the film and the resulting detachment of the film from the hollow body in the plastic phase and the subsequent lowering of the temperature to the glass phase , the film remains detached from the hollow body and for this reason i s easily removable .

[0056] EXAMPLES

[0057] Purely by way of example , experimental tests were carried out with films 1 made of a layered material having a base layer of anisotropic thermoretractable PET or PETG, i . e . , thermoretractable in a single direction; further tests were carried out with PET , PETG, PVC, PE or PP films , even combined with each other . A sleeve is created from the layered material on which a graphic design is printed with sublimation inks, the sleeve being fitted around the hollow body, heated to a temperature causing the sleeve to thermoretract around the hollow body to form the film adhering to the hollow body and the network of microchannels. Heat is applied up to an ink sublimation temperature, to transfer the graphic design onto the hollow body; simultaneously, the excess gas produced in the sublimation is extracted through the network of microchannels .

[0058] The film 2 is then brought or kept into / in the plastic phase to a temperature between 80° and 120°C; then pressurized fluid (e.g. air) is supplied to the microchannels at a pressure between 0.5 and 2 bar for a few seconds, so as to cause an 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 into the glass phase to a temperature below 80°C; lastly, the film 2 in the glass phase is removed.

[0059] The film 2 has a glassy behaviour below the glass transition temperature Tg, which for the materials used is lower than 80°C, and a plastic behaviour in the temperature range between the glass transition temperature Tg and the melting temperature Tf, which for the materials used is higher than 120°C and typically higher than 200°C.

[0060] Lastly, it is clear that the present invention encompasses further variants to the embodiments described herein, which fall within the scope of protection of the appended claims .

Claims

CLAIMS1. A method for removing a printing film from a hollow body, in particular from a bottle, wherein the film (2) in thermoplastic material, in particular with a base layer in a semicrystalline polymer, in particular PET or PETG, adheres to a hollow body (3) following thermoretraction so as to form a network of micro-channels, the method comprising:- bringing the film (2) to a temperature, in particular between 80° and 120°C, such as to place or maintain the film(2) into / in the plastic phase;- supplying a pressurized fluid to the micro-channels at a pressure, in particular between 0,5 and 2 bar, such as to detach at least partly the film (2) from the hollow body(3) when the film (2) is in the plastic phase;- bringing the film (2) to a temperature, in particular lower than 80°C, such as to place the film (2) detached from the hollow body (3) into the glass phase;- removing the film (2) when the film (2) is in the glass phase.

2. The method as claimed in claim 1, wherein removing the film (2) comprises cutting the detached part of the film (2) to start tearing the film (2) .

3. The method as claimed in claim 2, and comprising cutting the film (2) by means of a laser beam.

4. The method as claimed in claim 1, wherein removingthe film (2) comprises supplying pressurized fluid, in particular at a pressure between 2 and 10 bar, between the hollow body (3) and the film (2) when the film (2) is in the glass phase so as to cause the film (2) to burst.

5. The method as claimed in any one of the foregoing claims, wherein the hollow body (3) comprises an opening (7) , the method comprising supplying the pressurized fluid at said opening (7) by means of a fitting (6) communicating with a pressurized fluid source.

6. The method as claimed in claim 5, wherein said fitting (6) is wrapped in said film (2) together with the hollow body (3) to form an assembly (5) and comprises a channel (14) communicating with the pressurized fluid source and with said micro-channels.

7. The method as claimed in claim 6, and comprising clamping the assembly (5) before supplying the pressurized fluid between a pocket (10) and a counter- thrust device (18) .

8. The method as claimed in any one of the foregoing claims, and comprising supplying the pressurized fluid inside the hollow body (3) .

9. The method as claimed in any one of the foregoing claims, and comprising advancing the hollow body by means of a conveyor (4) simultaneously with the supply of the pressurized fluid.

10. The method as claimed in claim 9, and comprisingsupplying pressurized fluid to the micro-channels during the advance of the conveyor (4) .

11. A printing film removal machine for removing a printing film from a hollow body (3) , in particular from a bottle, for implementing the method as claimed in any one of the foregoing claims, the machine (1) comprising:- a blower (16) for supplying a pressurized fluid to the micro-channels at a pressure such as to detach at least partly the film (2) from the hollow body (3) when the film (2) is in the plastic phase; and- a cooling system (19) such that the film (2) detached from the hollow body is in the glass phase.

12. The machine as claimed in claim 11, and comprising a conveyor (4) to advance the hollow body (3) and the respective film (2) along a predetermined path (P) .

13. The machine as claimed in claim 11 or 12, and comprising a cutting tool (20) to make a cut in the film and start tearing the film (2) , in particular the cutting tool (20) is a laser emitter.

14. The machine as claimed in one of claims 11 to 13, and comprising a fitting (6) and a manifold (15) to connect the hollow body (3) to the blower (16) .

15. The machine as claimed in claim 14, and comprising a counter-thrust device (18) to clamp the hollow body (3) between the conveyor (4) and the counter-thrust device (18) .

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