Thermal sublimation printing method and system for hollow body

Abstract

A method of thermal sublimation printing of a hollow body having a continuous edge defining an end region. The method comprises: shrinking a heat-shrinkable sleeve (11) sleeved around the hollow body (2) to form a film (17), the inner surface of the heat-shrinkable sleeve (11) being printed with sublimation ink, the film (17) being arranged around the hollow body (2) and having an end flange (12) folded around a continuous edge (3) in an end region; pushing the assembly (16) formed by the hollow body (2) and the membrane (17) at the edge (3) towards an elastic yielding layer (21) of the sealing device (19); heating the component (16) to a sublimation temperature at which the ink is sublimated; and simultaneously suctioning air and gas from a plurality of microchannels arranged between the membrane (17) and the hollow body (2).

Description

Cross-references to related applications

[0001] This patent application claims priority to Italian Patent Application No. 102023000011223, filed on June 1, 2023, the entire disclosure of which is incorporated herein by reference. Technical Field

[0002] This invention relates to a thermal sublimation printing method for hollow bodies having edges defining end regions, particularly suitable for printing on the outer surface of hollow containers (such as bottles, jars, glasses, or containers made of ceramics or similar materials). Background Technology

[0003] Specific equipment and processes are known for producing decorations by heating and transferring ink (especially by thermal sublimation printing).

[0004] In this field, there is a growing demand for high-quality thermal sublimation printing, such as high-resolution patterns and precise alignment of decorations or text with a specific reference point on the hollow body.

[0005] Specifically, patent WO 2021 / 260613 A1 indicates how to apply decorations to hollow glass bodies (such as bottles or containers) using a sublimation printing process, which offers a high level of quality in terms of decorative clarity and adhesion precision. The process described in this patent involves fabricating a sleeve with an irregular inner surface, made of a film sheet of a thermoplastic material (typically PET or PETG), rolling the film sheet to form a cylinder, and heat-sealing the sleeve using adhesive or a solvent from the polymer itself using a sealing machine. The sleeve is patterned along its irregular inner surface. The pattern is printed directly onto the film using sublimation ink, which is intended to be transferred to the hollow body to be decorated via the sublimation process.

[0006] The overall process includes: placing a sleeve around a hollow body; heating the sleeve to shrink it and adhere it to the hollow body; heating the sleeve and hollow body at the ink sublimation temperature to sublimate the ink particles, transferring the pattern onto the hollow body; and simultaneously venting excess gas generated during sublimation through a microchannel network extending between the shrunken sleeve and the hollow body. The microchannels between the hollow body and the shrunken sleeve are due to the sleeve's irregular or rough inner surface, which is prepared to form microchannels when the sleeve shrinks to form a thin film that adheres to the hollow body.

[0007] The process described in WO 2021 / 260613 A1 is particularly satisfactory because it addresses quality issues. However, one challenge in dye-sublimation printing is how to combine high-quality levels with efficient industrialization of the production process to reduce production costs. Summary of the Invention

[0008] One object of the present invention is to provide a simple and effective industrial-scale method for thermal sublimation printing of hollow bodies.

[0009] According to the present invention, a method for thermal sublimation printing of a hollow body is provided, the hollow body having a continuous edge defining an end region, the method comprising: The heat shrink sleeve fitted around the hollow body is shrunk to form a film. The inner surface of the heat shrink sleeve is printed with sublimation ink. The film is arranged around the hollow body and has end flanges that fold around a continuous edge in the end region. The component formed by the hollow body and the thin film is pushed at the edge towards the elastic yield layer of the sealing device; Heating the component to its sublimation temperature; and At the same time, air and gas are drawn in from multiple microchannels arranged between the membrane and the hollow body.

[0010] According to the present invention, the connection of the component to the suction or vacuum source only requires pressing the component onto the elastic yield layer of the support device and suctioning air through the microchannel. This technical solution greatly simplifies the equipment and process itself required to implement the process.

[0011] Advantageously, the method is designed to draw air and gas from the end region through a sealing device.

[0012] Specifically, the method includes fitting a heat-shrinkable sleeve around the hollow body, such that the end flange of the sleeve protrudes from the edge of the hollow body; and folding the end flange to extend into the end region by heat shrinking around the edge.

[0013] In this way, the end flange folded into the cavity of the hollow body actually defines the exhaust area of ​​the microchannel together with the hollow body itself.

[0014] According to one embodiment of the invention, in the shrinkage step, one end flange protrudes relative to the edge of the hollow body to form a protrusion; the method includes a step of heat-sealing the protrusion to make suction within the microchannel more effective.

[0015] Another object of the present invention is to provide a thermal sublimation printing system for hollow bodies that overcomes the shortcomings of the prior art.

[0016] According to the present invention, a system for thermal sublimation printing of a hollow body having an edge defining an end region is provided. The system includes a sublimation furnace; and at least one sealing device configured to contact an assembly formed of the hollow body encased in a film having end flanges disposed in a corresponding end region defined by the edge of the hollow body. The sealing device includes a rigid body and an elastic yielding layer disposed at least along the contact portion of the hollow body defined by the edge covered by the film.

[0017] In this method, the supporting device serves to prevent or at least limit the suction of air from outside the end region defined by the edge.

[0018] Advantageously, the sealing device includes at least one opening in communication with the suction source for drawing air through the sealing device.

[0019] Specifically, elastic yield layers with hardness between 20 and 80 Shore hardness have been found to have good properties.

[0020] According to one variant, the support device includes an intermediate layer comprising elements having recesses and protrusions along the surface toward the elastic yield layer, the purpose of which is to apply uneven pressure on the edges of the hollow body and prevent the microchannels at the edges from closing.

[0021] Specifically, the intermediate layer comprises an elastically yielding material in which the element is embedded.

[0022] According to one embodiment of the invention, the roughness Ra of the supporting surface of the elastic yield layer is between 5 micrometers and 200 micrometers, so as to apply uneven pressure along the continuous edge of the hollow body and prevent the microchannels at the continuous edge from closing.

[0023] Specifically, silicone has been found to be particularly suitable for manufacturing elastic yield layers because it has elastic properties and can maintain these properties over a wide temperature range.

[0024] Specifically, the system includes two sealing devices configured to seal the component at opposite edges.

[0025] In this way, there is no need to heat seal the protrusion, and a shorter sleeve with a length that is only slightly longer than the hollow body can be used. Attached Figure Description

[0026] Other features and advantages of the invention will become clear from the following description of non-limiting embodiments of the invention, and with reference to the accompanying drawings, wherein: Figure 1 This is a schematic view of a thermal sublimation printing system (some parts are omitted for clarity). Figure 2 and Figure 3 yes Figure 1 Details of the assembly station of the medium system are shown in the side cross-sectional views of the two corresponding operation steps (some parts are omitted for clarity). Figure 4 yes Figure 1 Side view of the assembly station of the intermediate system (some parts are omitted and some parts are shown schematically for clarity). Figure 5 yes Figure 3 Another detail of the middle assembly station is a side cross-sectional view (some parts are omitted for clarity). Figure 6 yes Figure 1 Side view of the heat sealing station (some parts are omitted for clarity); Figure 7 yes Figure 1 A side cross-sectional view of the details of the sublimation station in the middle system (some parts are omitted for clarity). Figure 8 yes Figure 7 A magnified cross-sectional view of the details (some parts are omitted for clarity). Figure 9 yes Figure 8 Exploded perspective view with details in the middle; Figure 10 yes Figure 1 Side view of the sublimation station of the intermediate system (some parts are omitted for clarity); Figure 11 yes Figure 8 A side view of the sublimation station (some parts are omitted for clarity); and Figure 12 This is a side cross-sectional view of the details of the sublimation station according to a variant of the present invention (some parts are omitted for clarity). Detailed Implementation

[0027] refer to Figure 1 Figure 1 shows a sublimation printing system, which includes an assembly station S1, a heat sealing station S2 and a sublimation station S3 arranged sequentially along a forward path P.

[0028] exist Figure 2 In the attached drawing, reference numeral 2 denotes a glass-shaped hollow body having an annular closed edge 3 that defines an end region, which in the illustrated example includes a cavity 4. In the illustrated example, the hollow body 2 has a bottom wall 5 and side walls 6, the side walls 6 terminating at the edge 3.

[0029] Reference numeral 7 indicates an assembly device extending along axis A1, comprising a plate 8, a shaft 9 extending through the plate 8 and adjustable relative to the plate 8 along axis A1, and a support element 10 disposed at the top of the shaft 9. The assembly device 7 is configured to support an inverted hollow body 2, the support element 10 contacting the inner surface of the bottom wall 5 of the hollow body 2, and maintaining a given distance between the edge 3 and the plate 8.

[0030] refer to Figure 3 The plate 8 serves to define a supporting surface for a sleeve 11 made of heat-shrinkable material, which is disposed around the hollow body 2. This material is heat-shrinkable only in the circumferential direction of the sleeve 11. Furthermore, the inner surface of the sleeve 11 is rough or irregular to form a dense network of microchannels or channels when the sleeve 11 shrinks and comes into contact with the hollow body 2, and is printed with sublimation ink. Alternatively, the printed inner surface of the sleeve 11 is smooth, while the outer surface of the hollow body 2 is rough to similarly form a dense network of microchannels when the sleeve 11 shrinks and conforms to the outer surface of the hollow body 2 (particularly the outer surface of the sidewall 6). The pattern is printed directly onto the sheet using sublimation ink intended to be transferred onto the hollow body 2 to be decorated. This sheet is readily heat-sealed along its two opposite ends to form the sleeve 11, the inner surface of which is decorated with the pattern.

[0031] The sleeve 11 is taller than the hollow body 2 and has an end flange 12 protruding from the edge 3 of the hollow body 2 and an end flange 13 protruding from the bottom wall 5.

[0032] Therefore, the assembly device 7 can precisely fit and position the sleeve 11 onto the hollow body 2 so that the decoration is arranged at a given position relative to a specific reference point of the hollow body 2, and appropriately adjust the protrusion of the flanges 12 and 13. In this case, the length of the end flange 12 is much smaller, only sufficient to fold the end flange 12 around the edge 3 to prevent the folded end flange 12 from blocking the cavity 4. The length of the end flange 13 is sufficient to allow it to be joined and heat-sealed.

[0033] refer to Figure 4 System 1 includes a conveyor 14 for advancing the assembly device 7 along path P through assembly station S1, assembly station S1 including heat shrink oven 15, in which sleeve 11 shrinks around hollow body 2 to form component 16 with hollow body 2. Figure 5 Conveyor 14 is configured to advance multiple assembly units 7 sequentially and / or side-by-side along the forward path P.

[0034] refer to Figure 5 The contracted sleeve 11 actually forms a thin film 17 that fits the sidewall 6 and bottom wall 5 of the hollow body 2, has a protrusion 18 formed by the contraction of the end flange 13, and the end flange 12 is folded around the edge 3 and extends into the end region, in this case into the cavity 4.

[0035] Subsequently, the assembly device 7 and component 16 are advanced to the heat sealing station S2 via the conveyor 14, where the protrusion 18 is heat-sealed, as shown in the image. Figure 6 As shown.

[0036] refer to Figure 7 After the heat sealing operation is completed, component 16 is placed on the corresponding sealing device 19, which is configured to move along the conveying path P through the sublimation station S3. Figure 10 In the example shown, the sealing device 19 also functions as a support device.

[0037] refer to Figure 8 The sealing device 19 includes a rigid body 20 and an elastic yielding layer 21 arranged at least along the support portion of the assembly 16, defined by an edge 3 covered by a membrane 17.

[0038] refer to Figure 7 The sealing device 19 has an opening 22 communicating with the suction source 23 for drawing air through the rigid layer 20 and the elastic yielding layer 21.

[0039] refer to Figure 8 The elastic yield layer 21 serves to prevent air from being drawn in from the outside and facilitates a hardness of 20 to 80 Shore A, preferably made of silicone. The sealing device 19 also includes an additional intermediate layer 24 made of an elastic yield material, in which an element 25 is embedded. The surface of the element 25 facing the elastic yield layer 21 has an alternating structure of recesses and protrusions, preferably a metal mesh embedded in the intermediate layer 24. Figure 8 In the example shown, element 25 is defined by a mesh (particularly a metal mesh). Opening 22 also extends through intermediate layer 24.

[0040] The roughness Ra of the support surface of the elastic yield layer 21 is between 5 and 200 micrometers.

[0041] refer to Figure 9 The rigid layer 20 is essentially a metal plate, the exterior of which is defined by sidewalls 26 for accommodating the elastic yield layer 21 and possibly the intermediate layer 24.

[0042] The sealing device 19 includes a conduit 27, which serves to support the rigid body 20 at the opening 22 and is connected to the suction source 23. Figure 7 ).

[0043] refer to Figure 10 The sublimation station S3 includes a sublimation furnace 28 and a conveyor 29, which is configured to move a plurality of sequentially arranged sealing devices 19 forward through the sublimation furnace 28.

[0044] When in use, at assembly station S1 ( Figure 4 In this process, the sleeve 11 is fitted around the hollow body 2 and contracted to form a thin film 17 with corresponding protrusions 18, and the end flange 12 is folded around the edge 3 and extends into the end region, in this case extending into the cavity 4 of the hollow body 2 (according to...). Figure 5 (As shown).

[0045] At heat sealing station S2 ( Figure 6 After the protrusion 18 is heat-sealed in the assembly, the component 16 formed by the hollow body 2 and the film 17 is transferred to the sublimation station S3 via the assembly device 7. Figure 10 The sealing device 19 of the conveyor 29 of the sublimation furnace 28 is used to seal the conveyor 29. Figure 10 The support component 16 is located in the hollow body 2 and is able to discharge the gas and vapor generated between the thin film 17 and the hollow body 2 during the thermal sublimation process.

[0046] Due to the roughness of the inner surface of the film 17 and / or the surface of the hollow body 2 to which the film 17 is attached, there are microchannels (not shown in the figures) between the film 17 and the hollow body 2, which allow air and gas to pass through.

[0047] When component 16 is placed on sealing device 19 at edge 3 of hollow body 2, the weight of component 16 causes elastic yield layer 21 at edge 3 to deform ( Figure 8 The surface roughness of the elastic yield layer 21 and / or the presence of the intermediate layer 24 prevent uniform pressure from being applied along the edge 3 and prevent the microchannels at the edge 3 from closing when the pressure applied by the component 16 increases. When the suction source 23 ( Figure 8 During startup, a void is formed in the end region, allowing air and gas to escape through the microchannels. This void further increases the pressure exerted by component 16 on the sealing device 19 and the elastic yield layer 21, thereby enhancing the seal and restricting the entry of external air (which is permitted during startup).

[0048] In this step, the roughness of the support surface of the elastic yield layer 21 and / or the presence of the intermediate layer 24 also prevent the microchannels from closing, thereby enabling air and gas to escape from the printed surface.

[0049] According to a variant not shown in the accompanying drawings, the sealing device has multiple openings connected to a suction source. Thus, when the openings are sufficiently spaced apart and the component dimensions allow, the sealing device can process the same number of components as the number of openings simultaneously.

[0050] According to a variant not shown, the intermediate layer is omitted, and the mesh is arranged directly between the rigid layer and the elastic yielding layer.

[0051] The description of this invention specifically refers to hollow bodies in the shape of glass cups or vessels, but it is also applicable to hollow bodies of other shapes, such as... Figure 11 The bottle shown has an end region.

[0052] In this case, the hollow body 2 (in this case, a bottle) has an edge 3 defining the cavity 4 at the bottom of the bottle. The thermal sublimation process and system are the same as those used for vessels and glasses. In this case, it is advisable to hold the bottle in place to avoid tension on the film 17 at the bottle opening during the suction step.

[0053] According to another variant, the end region of the container is flat, i.e., without depressions or cavities.

[0054] In order to expel gas from the microchannel, it is important that the end flanges folded along the end region are not heat-sealed so that fluid communication can be established between the microchannel and the vacuum source, and it has been proven that fluid communication can be achieved even without recesses or cavities.

[0055] Furthermore, although the accompanying drawings show a sealing device with a flat surface, it should be understood that the surface of the sealing device can be of any construction, with the only consideration being its ability to conform to the continuous edges of the hollow body.

[0056] according to Figure 12 In another variant shown, sublimation station S3 includes, in addition to sealing device 19, another sealing device 30, which is arranged on the side opposite to the first sealing device 19 and configured to selectively contact the end of assembly 16 opposite to the end arranged on the first sealing device 19. Sealing device 30 has a rigid body 31 with a frustoconical surface 32; an opening 33 communicating with a suction source; and an elastic yield layer 34 arranged along the frustoconical surface 32. Between the rigid body 31 and the elastic yield layer 34, a layer similar to an intermediate layer 24 can be arranged. Figure 8 The middle layer of ).

[0057] In use, the hollow body 2 is a bottle, wrapped with a film 17, and held between sealing devices 19 and 30. In addition to having an edge 3 that defines the corresponding end region, the hollow body 2 also has another edge 35 that defines the corresponding end region on the side opposite to the edge 3.

[0058] One advantage of this embodiment is that it eliminates the need for modifications to the protrusion 18. Figure 7 Therefore, the heat sealing station S2 is omitted. Figure 1 and Figure 6Furthermore, this technical solution can significantly shorten the end flange 13, thereby saving a large amount of material. The suction via the sealing device 19 can also be omitted. Alternatively, the sealing device 30 may not have an opening or suction function. In practice, suction can be performed on both sides, or only on one side. In this embodiment, the end flanges 12 and 13 are very short, i.e., their length allows them to fold over the corresponding edges 3 and 35 without protruding from them, and also significantly saves thermoplastic film.

[0059] Finally, it is clear that the present invention includes other variations of the described embodiments, all of which fall within the scope of the appended claims.

Claims

1. A method for thermal sublimation printing of a hollow body, said hollow body having continuous edges defining end regions, characterized in that, The method includes: The heat shrink sleeve (11) fitted around the hollow body (2) is shrunk to form a film (17), the inner surface of the heat shrink sleeve (11) is printed with sublimation ink, and the film (17) is arranged around the hollow body (2) and has end flanges (12, 13) folded around continuous edges (3, 35) in the end region. The component (16) formed by the hollow body (2) and the film (17) is pushed at the edge (3, 35) towards the elastic yield layer (21, 34) of the sealing device (19, 30). The component (16) is heated to the sublimation temperature; and At the same time, air and gas are drawn from multiple microchannels arranged between the thin film (17) and the hollow body (2).

2. The method according to claim 1, characterized in that, The method includes drawing air and gas from the end region through the sealing device (19, 30).

3. The method according to claim 1 or 2, characterized in that, The method further includes: The heat-shrinkable sleeve (11) is fitted around the hollow body, such that the end flanges (12, 13) of the sleeve (11) protrude from the edges (3, 35) of the hollow body (2); and The end flanges (12, 13) are folded over to extend into the end region by heat shrinking around the edges (3, 35).

4. The method according to claim 3, characterized in that, In the heat shrinking step, the end flange (13) protrudes relative to the edge (35) of the hollow body (2) to form a protrusion (18); the method includes the step of heat sealing the protrusion (18).

5. A system for thermal sublimation printing of a hollow body, the hollow body having an edge defining an end region, characterized in that, The system includes: Sublimation furnace (28); At least one sealing device (19, 30) is configured to contact a component (16) formed of a hollow body (2) enclosed in a film (17) having end flanges (12, 13) arranged in a corresponding end region defined by an edge (3, 35) of the hollow body (2), wherein the sealing device (19, 30) includes a rigid body (20, 31) and an elastic yielding layer (21, 34) arranged at least along the contact portion of the hollow body (2) defined by the edge (3, 35) covered by the film (17).

6. The system according to claim 5, characterized in that, The sealing device (19, 30) includes at least one opening (22, 33) in communication with the suction source (23) for drawing air through the sealing device (19, 30).

7. The system according to claim 5 or 6, characterized in that, The hardness of the elastic yield layer (21, 34) is between 20 Shore hardness and 80 Shore hardness.

8. The system according to any one of claims 5 to 7, characterized in that, The sealing device (19, 30) includes an intermediate layer (24) which includes an element (25) having recesses and protrusions along the surface toward the elastic yield layer (21, 34).

9. The system according to claim 8, characterized in that, The intermediate layer (24) comprises an elastic yielding material, and the element (25) is embedded in the elastic yielding material.

10. The system according to any one of claims 5 to 9, characterized in that, The surface roughness Ra of the free surface of the elastic yield layer (21, 34) is between 5 micrometers and 200 micrometers.

11. The system according to any one of claims 5 to 10, characterized in that, The elastic yield layer (21, 34) is made of silicone.

12. The system according to any one of claims 5 to 11, characterized in that, The sealing device (19) has a plurality of openings (22) connected to the suction source (23).

13. The system according to any one of claims 5 to 12, characterized in that, The system includes two sealing devices (19, 30) configured to clamp the component (16) at two opposite edges (3, 35).

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