WO2019130143A1

WO2019130143A1 - Method for speeding up the hot stamping of a substrate

Info

Publication number: WO2019130143A1
Application number: PCT/IB2018/059923
Authority: WO
Inventors: Stefano Aurelio BROZZI
Original assignee: Primatech S.R.L.
Priority date: 2017-12-28
Filing date: 2018-12-12
Publication date: 2019-07-04

Abstract

Method for speeding up the stamping process in a hot stamping machine (1), characterised in that it introduces treated air, in at least two processing steps that are separate and clearly distinct from each other, on the surface heated by at least one heating element (6) of a support grill (3), by means of a plurality of nozzles (10), suitably supplied by at least one supply duct (14), in turn directly connected with at least one air filter (16), at least one air dehumidifier (11), at least one compressor and at least one heating element (6) arranged in proximity of said nozzles (10), so as to maintain all the cliche plates (2) arranged above said support grill (3) at predetermined and constant temperature, humidity and pressure values, said method being suitable to introduce the aforementioned treated air in the following two steps: First Step, immediately after stamping, in order to speed up the detachment of a foil from its plastic medium (4) and of a sheet (5) just stamped from the cliche plates (2), thus allowing grippers (8) to quickly remove it from the stamping area; Second Step, during the positioning of a new sheet (5) to be stamped by the grippers (8) above said cliche plates (2) in order to maintain it perfectly stretched, said method being capable, due to the aforementioned two introductions of treated air into the stamping area, of maintaining said stamping area constantly in overpressure with respect to the surrounding environment, so that the air only flows from inside said stamping area to the surrounding environment.

Description

“Method for speeding up the hot stamping of a substrate”

Description

Field of the art

The present industrial invention patent application, refers to the field of stamping machines and in particular it describes a new hot stamping machining method.

Prior art

Hot stamping is an extremely high quality typographic printing system. Hot stamping uses cliche plates or characters for transferring a film provided with various tones on a substrate usually in paper format and flat. Hot stamping can be metallised or with pastel shades, fixed on objects with regular and flat surfaces, such as paper substrates, or variously composed. Hot stamping is preferably carried out on a cardboard paper, but products made of plastic materials, shoppers, labels, cosmetic packagings, etc. can also be used.

Hot stamping is based on a simple and efficient concept. As a matter of fact, the stamping or hot stamping process is obtained by engraving, better known as cliche plate which is reversibly fixed on the plate or support grill, which is heated in turn. The foil, i.e. the film to be used for hot stamping, once heated up to the pre-set temperature, is interposed between the medium to be treated, usually the paper or cardboard and the engraving, i.e., the cliche plates. The film or foil is usually a polyester film, which is eliminated, provided with a laminated layer generally with an aluminium base which remains engraved on the paper substrate. When the stamping press is actuated, the cliche plate presses the film or foil against the sheet to be stamped, the heat transmitted by the cliche plate detaches the colouring layer of the foil from the film, which is eliminated, while the colouring layer is irreversibly applied on the paper sheet or cardboard which is thus stamped. Such hot stamping technique, if not expressly specified, is implied to always regard plane hot stamping. A method that does not produce the relief of the image per se, unless particular hot stamping engravings are used to produce in relief too, in combination. As a matter of fact, the hot stamping is the only stamping method, capable of conferring brilliance and metal effect on any substrate, preferably of the paper type. Effects that remain and do not lose shininess over time. Other types of stamping, screen printing and cold foil stamping are available in the market, but they do not offer the same quality characteristics. Normally, this technique is preferably carried out on a paper and on cardboard, but it can even be applied on plastic polymers and other composite media. However, hot stamping foils are not limited to conferring metal finishes, such as gold, silver or the like, but stamping films are currently available in the market with wide variety of colours with particular effects such as marble, hide or skin, wood veins, pearlescence, repeated patterns, holograms, pigments and tenuous tones, with both opaque and shiny finishes.

There are major differences between the foils used, not only the characteristics of the colour and surface are determined, but also the duration, chemical resistance, friction resistance as well as colour loss resistance, fragility, opacity and adherence characteristics. Different companies of the industry produce ranges of foils widely available in the market that can vary widely. Even foils that seem identical can have different not immediately identifiable characteristics, due to the fact that they are designed for different applications. Like any other creative means, these aesthetic-technical characteristics must be perceived as an exploration opportunity: as a matter of fact, all these are essential variables that affect the success of the initial project same case applying to the inherent quality of the selected media as well as the depth and complexity of the engravings. Thus, hot stamping is an extraordinarily complex and versatile graphic enhancement process as well as an images enhancement process, applicable in media on which conventional stamping techniques cannot be applied. The complexity and precision of this stamping method requires rigorous processing parameters, whose absence immediately affects the quality of the end product. The major problems related to techniques and methods used up to now in hot stamping, are essentially related to maintaining a predetermined and desired temperature of the cliche plates, during the sensitive stamping steps and in particular in proximity of the steps regarding loading, stamping and removing the just hot-stamped sheet. In order to speed up the aforementioned removal, grippers, which being engaged on one side of the just stamped sheet, delicately but rapidly remove it from the stamping machine, once an air jet has detached it from the cliche plates which had stamped the colour present on the film or foil, are usually used. This being the most complex and slow step of the entire hot stamping process, it is easy to understand that the speed for detaching and removing the sheet just stamped and thus the productivity of the entire process, is directly correlated to the speed of execution of this sensitive step of the stamping process. In order to speed up this crucial step, rather powerful air jets which, directly blowing on the cliche plates, detach the film and speed up the cooling of the foil just printed, separating the medium, which is eliminated, from the laminate deposited on the sheet, are usually used. The amount of blown compressed air is directly correlated to the number of cliche plates present on the support grill and the size of the sheet to be stamped. Unfortunately, all this compressed air introduced to obtain the quick detachment of the sheet from the cliche plates, by means of a sequence of suitably oriented special nozzles, also causes the unwanted cooling of the cliche plates which, by consequence, must be constantly heated by a special heating element present in the support grill which supports the cliche plates. Thus, whereas it speeds up the detachment step on the one hand, on the other hand the considerable amount of compressed air injected onto the cliche plates when stamping a substrate, simultaneously cause the excessive cooling of the cliche plates. This unwanted thermal variation considerably deteriorates the stamping quality, the heating element present on the support grill tries to recover this thermal dispersion, increasing the heating element action and the energy consumption correlated to the maximum use of the heating element. However, this thermal variation is often such to have to slow the execution of the stamping. Hot stamping is an extremely high quality, relatively quick and substantially economical production method. The difference from other expensive industrial processes, such as metallisation, substantially lies in the fact that the latter is used when one wants to entirely cover a substrate or an object. Thus, the main strong point of hot stamping lies in reproducibility considering an extremely high processing quality, alongside the total preservation of decorum on any surface over time. Thus, the technical problems revealed by this tested method are still related to the rigorous maintenance of the thermal and hygroscopic parameters in which it is carried out. These parameters essentially are temperature, humidity and applicability, correlated to the cliche plates and to the detachment of the substrate stamped by the latter. Furthermore, hot stamping can be combined with other stamping techniques such as screen printing and pad printing, thus further complicating the stamping procedure, requiring strict compliance with the aforementioned parameters. This possibility represents a further added value in packaging stamping with particular design, like those for the perfume or cosmetic industry. As a matter of fact, hot stamping is also used for high-end products, in the perfume, cosmetic and beverage industries. In other words, all industries in which packaging requires refined decorations aimed at conveying an idea of style and accurateness. Thus, constantly maintaining a predetermined quality standard is crucial to a method that specifically allows to boost the appeal of a given work, enhancing its chromatic shades. Hot stamping machines are considerably automated hot stamping machines, with presses consisting of a fixed upper plane and a moveable lower plane. The quick movement of the moveable lower plane, required to position the sheet to be stamped and detaching the cliche plates, also represents a further problem for the correct maintenance of the ideal temperature. The sudden and repeated lowering and rising of the moveable lower plane creates a violent circulation of air which further destabilises the homogenisation of the temperature of the cliche plates, thus creating unwanted and unpredictable thermal variations thereof.

Description of the invention

The present industrial invention patent application sets out to solve all the aforementioned problems by describing a new method for speeding up, monitoring and stabilising the hot stamping process while simultaneously keeping the high quality and aesthetic values intact. Hot stamping is substantially a tested stamping method that identifies, in the transfer, a given metal or plastic film or foil on the surface of the object or of the substrate to be stamped, due to the pressure exerted by a cliche plate supported by the action of the heat. The stamping thus obtained can be variously coloured: gold, silver and other infinite colours currently easily available in the market, capable of creating delicate and captivating optical effects. This sophisticated technique currently allows obtaining particular decorations, logos, lines or ribs, all provided with the typical liveliness of metal stampings irrespective of the selected colour. The decoration transferred through the hot stamping is brilliant and capable of enhancing any packaging to the maximum, on condition that it be carried out at the studied and pre-set temperature. The strictness with which the stamping parameters are established and optimised is particularly important in the hot stamping technique, just like the correct maintenance of these parameter during the entire production process is equally important. It is thus important to avoid heat excursions on the cliche plates which could lead to quality drop or, worse, partial or incorrect transfer of the film on the paper substrate to be stamped. In light of these observations, it is clear that the temperature of the cliche plates is the main parameter to be monitored and maintained stable so as to be able to obtain an excellent and constant performance of the stamped product. Cliche plates are orderly arranged on the entire support grill and are positioned in a manner such to homogeneously cover the portions thereof. The support grill is instead a flat surface, possibly drilled, which supports the cliche plates and it is made of a solid metal alloy with a heating element that extends along it entirely embedded therein. This heating element homogeneously heats the entire support grill so that the latter in turn homogeneously and constantly transfers the heat produced by the underlying heating element to all cliche plates. The latter are orderly arranged above it so as to optimise the performance of the substrate to be stamped and they are also made of metal or metal alloys. The transfer and, above all, the maintenance of the desired heat in the cliche plates is crucial towards obtaining an aesthetically and technically perfect product. Automated grippers are used in order to speed up the positioning and removal of the sheets just stamped. Many small compressed air jets facilitate and speed up the detachment of the foil both from the plastic medium that supported it and from the cliche plates that stamped it, thus facilitating the stamping action carried out by the press. Thus, the plastic medium is eliminated and the foil is this transferred on the sheet that will have engraved the desired graphic effect. This mechanical action carried out by the compressed air flow facilitates and, above all, speeds up the action of the grippers which, upon occurrence of the detachment of the plastic medium from the foil closing delicately, quickly remove the hot-stamped sheet from the press which will have opened in the meanwhile. Unfortunately, the synchronous and prompt action of the air jets, essentially concentrated in the peripheral area of the support grill, i.e., concentrated where the grippers act and are arranged to remove the stamped sheets, inevitably leads to the cooling of that portion of the support grill and above all, even much worse, it leads to the cooling of the peripheral cliche plates positioned thereon. Thus, the asymmetrical and peripheral action of the air jets causes thermal asymmetry in the support grill. The thermal drop of the peripheral portion of the support grill is directly transferred on the peripheral cliche plates which are heated by the latter only, thus causing an aesthetic deformity in the single stamped products during that hot stamping action. Furthermore, the opening and closing movement of the stamping machine, thus causing the rising and lowering of the moveable lower plane, creates an unwanted pump effect which destabilises and cools the cliche plates further by rhythmically introducing air into the stamping area at room temperature. All these problems are usually overcome by slowing the entire production process so as to allow the heating element arranged inside the support grill to heat the entire grill and thus the single cliche plates once again and uniformly. Despite overcoming or at least reducing the problem related to the cooling of the peripheral cliche plates, this method considerably slows the production process, thus drastically dropping the productivity and the efficiency of the entire production process. In order to overcome this complex problem, the present patent application aims at describing an innovative articulated method for managing compressed air jets, so as to obtain the quick detachment of the stamped substrate from the cliche plates, but without reducing the quality of the heated supports and thus the production capacity of a plant using the hot stamping technique. Thus, the present industrial invention patent application intends to describe and claim an innovative and a new machining method, suitable to organise and maintain the flow of the compressed air introduced by the nozzles at a predetermined temperature and humidity, simultaneously avoiding the introduction of air into the hot stamping area at room temperature, due to the sudden displacement of the moveable lower plane of the stamping machine.

Description of the figures

The invention will be described hereinafter in at least one preferred embodiment, provided by way of non-limiting illustration, with reference to the attached figures, wherein:

- FIGURE 1 is a front view of the stamping area, visible in which is the support grill 3, provided with a plurality of holes 7, shown above the support grill 3 are nine cliche plates 2, present inside the support grill 3 are the heating elements 6 suitable to heat it.

- FIGURE 2 is a perspective view of a plurality of nozzles 10 for introducing the treated air, in which the line for supplying the treated air 14 and the actuator 9 of each single nozzle 10 can be seen.

- FIGURE 3 is a view of the hot stamping area in which a battery of the actuators 9 of the nozzles 10 for introducing the treated air can be seen, oriented in a manner such to impact the cliche plates 2 with their flow of treated air, thus facilitating both the correct positioning and the detachment of the sheet 5 from the cliche plates 2 and from the plastic support film 4.

- FIGURE 4 is an overall view of a hot stamping machine 1, according to the present invention in which the grippers 8 for the quick displacement of the sheets 5, the air filter 16 and the dehumidifier 11 can be seen.

Detailed description of the invention

The hot stamping machine 1 according to the present industrial invention, is provided with an innovative and complex system for treating the air used provided, in sequence, with a common air intake, connected with a filter 16 for purifying the suctioned air, with a system for dehumidifying the previously filtered air, provided with at least one air dehumidifier 11, with a common compressor for the previously filtered and dehumidified air which thus, after being compressed, is supplied to said treated air supply line 14, as well as special heating elements 6 and 15, suitably arranged along the supply line 14 and/or in proximity of at least one nozzle 10, suitable to heat the previously filtered, dehumidified and compressed air and lastly supplied by the supply line 14 to said nozzles 10. From said nozzles 10 the treated air is emitted into two different steps: in a first step it is directed towards the cliche plates 2 for facilitating the detachment of the foil 17 from the plastic medium 4 thereof and from the cliche plates 2 lastly facilitating the detachment of the sheet 5 just stamped from the latter; in a second emission step, the treated air is directed so as to facilitate the correct positioning of the new sheet 5 to be treated above the various cliche plates 2 which, creating a slight overpressure, allows preventing the inflow of air into the hot stamping area at room temperature. The latter effect is important for stably maintaining the air of the entire hot stamping area at the desired parameters. The two distinct emissions of treated air maintain, in the stamping area, a slight overpressure which makes the direction of the air flowing out from the stamping area unique. Basically, preventing the unwanted inflow of impure air from the surrounding environment into the stamping area. The heating elements 6 and 15 have the purpose of maintaining the temperature of the treated air emitted by the nozzles 10 high, between 70 and 140 degrees centigrade, so as to allow both the quick detachment of the substrate 5 as soon as it is hot-stamped by the cliche plates 2 and the positioning of the new sheet 5 to be stamped alongside maintaining the desired temperature of the cliche plates 2. Thus, the air treatment method subject of the present patent application sets out to describe a sophisticated system for managing the treated air, i.e. suctioned, filtered, dehumidified, compressed and heated, which is suitably oriented both to speed up the detachment of the sheet 5 just stamped by the cliche plates 2 and the correct positioning of the new sheet 5 to be stamped supporting the action of the grippers 8 and oriented so as to prevent the inflow of air into the hot stamping area at room temperature. Thus, described and claimed herein is an innovative method for managing the treated air in any hot stamping machine, characterised by two distinct emissions of treated air which is emitted by the nozzles 10, in two distinct and different time phases. I.e., the first oriented parallel to the plane consisting of the support grill 3, directed towards the cliche plates 2 and immediately subsequent to the step for stamping the sheet 5; the second emission instead is suitable to support the action of the grippers in correctly positioning the new sheet 5 to be stamped on the cliche plates 2, by laying it. In both cases, the treated air is heated at a temperature comprised between 70 and 140 degrees centigrade, preferably 100 degrees centigrade. In particular, the second introduction of the treated air by the nozzles 10 is designated to prevent the sheet 5, displaced by the grippers 8, by lying above the cliche plates 2, from taking a non-perfectly flat position on the surface of the support grill 3, when the stamping machine 1 is regularly actuated, during the stamping cycle step of loading each single sheet 5. The second emission of treated air, vigorously impacting the sheet 5 to be treated, lays it perfectly simultaneously preventing air from the surrounding environment from flowing into the stamping area, i.e., onto the support grill 3. This unwanted inflow of air from the environment, caused by the simple sudden lowering of the moveable lower plane during the machining steps, would cause the unwanted suctioning of a considerable amount of air from the surrounding environment (piston effect). This air is dusty, moist and cold and it could bring impurities thus causing cooling in the stamping area and on the cliche plates 2. Thus, this second introduction of treated air serves to prevent the piston effect, created by the sudden lowering of the moveable lower plane and thus of the support grill 3 of the stamping machine 1, from causing the massive introduction of air onto the stamping plane and onto the support grill 3 at room temperature. Thus, the present industrial invention patent application, sets out to describe a multi-step method for managing the introduction of treated air into the stamping area which is characterised by two distinct steps for introducing treated air jets emitted by the nozzles 10 and that said air had been previously fully suctioned, filtered, dehumidified, compressed and heated according to specific pre-set parameters. The air to be introduced through the nozzles 10 must thus have been previously entirely suctioned and filtered in at least one specific filter 16 so as not to contain impurities or dust which could alter the stamping quality. Hence, said air thus filtered must be dehumidified and in particular dehumidified up to reaching a specific humidity content so as to guarantee optimal adherence of the stamped materials, due to the use of at least one common dehumidifier 11. Hence, the air thus filtered and dehumidified must be compressed by means of a common compressor so that it can lastly be heated by the heating elements 6 and 15 arranged both on the line 14 for supplying air and in proximity of the nozzles 10. The purpose of this production method is to introduce an innovative hot stamping method capable of making the quality and quantity parameters constant and high, so as to allow the hot-stamped substrate 5 to be quickly and perfectly positioned by the grippers 8, stamped, then quickly detached from the cliche plates 2 and subsequently quickly removed from the displacement devices such as grippers 8. The perfect and constant monitoring of the temperature and humidity in the stamping area, allows the hot stamping machine 1 to work at maximum operating speed, without being faced with the risk of potential deterioration of the quality of the manufactured product. The operating temperature at which the hot stamping plant is required to operate is normally between 70 degrees centigrade and 140 degrees centigrade, as a function of the type of foil 17 used. Upon identifying and choosing the desired foil 17, the temperature of the cliche plates 2 must remain at approximately around twenty degrees centigrade, preferably at around just four degrees centigrade. The distinctive trait of maintaining the jet of treated air emitted by the nozzles 10 at a temperature comprised between 70 and 140 degrees, preferably at around 100 degrees centigrade, allows to inject a massive amount treated air and at a quite high pressure, comprised between 2 and 7 bars, preferably 5 bars, on the sheet 5 to be positioned, hot-stamp and thus facilitate the quick detachment thereof from the cliche plates 2. This double introduction of treated air into the stamping area allows to speed up the step for positioning and the step for detaching the sheet 5 without simultaneously altering the temperature of the entire stamping area. These emissions of treated air create a barrier of treated air which thus prevents thermal excursions of the support grill 3, thus making the temperature of the entirety homogeneous, so that all the cliche plates 2 always maintain the desired temperature, irrespective of the speed at which the hot stamping plant 1 is actuated. The fact that no thermal deformity occurs on the entire support grill 3, irrespective of the production speed of the plant, guarantees a perfect performance of the hot stamping over time, thus providing a product that is perfect and similar in terms of technical and aesthetic characteristics, irrespective of the cliche plates 2 used, all the latter operating exactly at the same pre-set and desired temperature. In a distinctive embodiment of the invention, each single nozzle 10 is adjustable, both in terms of the direction of flow of the treated air as well as the intensity and temperature thereof, so as to direct the desired amount of treated air exactly in the planned direction, at the desired time and with the pre-set intensity and provided with the ideal temperature for that determined area of the support grill 3 or of the cliche plates 2. This stoichiometric management of the flow of treated air allows the optimal monitoring of the operation of the entire hot stamping area, thus allowing all cliche plates 2 to operate always and constantly at the pre-set temperature, their temperature being subjected to a double thermal control. The first control is provided by the heating element 6 arranged inside the support grill 3 while the second thermal control is obtained by the action of the two flows of treated air that flows out, at different times, from the nozzles 10. The management of the temperature of the entire hot stamping area can be supported by a common remote control system provided with a plurality of common sensors suitable to monitor each heating element 6 and 15, irrespective of whether it is arranged on the support grill 3, on the support grill 14 or on the nozzles 10, and thus also the temperature of each single cliche plate 2. The present industrial invention patent application sets out to provide an innovative hot stamping method which, maintaining the quality characteristics intact, allows to substantially and continuously enhance the production characteristics. The hot stamping production method according to the present invention patent application, can thus be provided with video cameras and thermal sensors which allow the monitoring thereof. In addition, nozzles 10 which, due to computerised actuators 9, suitably adjust the pressure, the direction and the temperature of the treated air emitted by each single nozzle 10 with the aim of semi-automatically managing the entire production process, can be used. The sudden temperature drop, even in a small area of the support grill 3 or of only one cliche plate 2, is immediately detected by said thermal sensors which, besides activating an alarm, automatically stop or slow production thus allowing the heating elements to restore the desired thermal values.

Claims

1. Method for speeding up the stamping process in a common hot stamping machine (1), characterised in that it introduces treated air, in at least two processing steps that are separate and clearly distinct from each other, on the surface heated by at least one heating element (6) of a support grill (3), by means of a plurality of nozzles (10), suitably supplied by at least one supply duct (14), in turn directly connected with at least one air filter (16), at least one air dehumidifier (11), at least one common compressor and at least one heating element (15) arranged in proximity of said nozzles (10), so as to maintain all the cliche plates (2) arranged above said support grill (3) at predetermined and constant temperature, humidity and pressure values, said method being suitable to introduce the aforementioned treated air in the following two steps: First Step, immediately after stamping, in order to speed up the detachment of the foil (17) from its plastic medium (4) and the sheet (5) just stamped from the cliche plates (2), thus allowing the grippers (8) to quickly remove it from the stamping area; Second Step, during the positioning of the new sheet (5) to be stamped by the grippers (8) above said cliche plates (2) in order to maintain it perfectly stretched, said method being capable, due to the aforementioned two introductions of treated air into the stamping area, of maintaining said stamping area constantly in overpressure with respect to the surrounding environment, so that the air only flows from inside said stamping area to the surrounding environment.

2. Method for speeding up the stamping process in a common hot stamping machine (1) according to claim 1, wherein the temperature of the treated air supplied by the supply duct (14) and emitted by the nozzles (10) is comprised between 60 and 150 degrees centigrade, preferably 100 degrees centigrade.

3. Method for speeding up the stamping process in a common hot stamping machine according to the preceding claims, wherein the pressure of emission of the treated air by the nozzles (10) is comprised between 2 and 7 bars, preferably 5 bars.

4. Method for speeding up the stamping process in a common hot stamping machine (1) according to the preceding claims wherein the stamping area and in particular the area above the support grill (3) is constantly maintained at a pressure slightly greater than that of the surrounding environment.

5. Method for speeding up the stamping process in a common hot stamping machine (1) according to the preceding claims, wherein the temperature of the cliche plates (2) is finely adjusted by a double heating system, i.e. by the system of the heating elements (6) arranged in the support grill (3) and by the air treated and heated to the desired temperature generated by the heating elements (15) arranged in proximity to the nozzles (11).

6. Method for speeding up the stamping process in a common hot stamping machine (1) according to the preceding claims, wherein the temperature of each cliche plate (2) is monitored by at least one heat sensor (18) suitable to allow the remote control, by means of common monitoring systems, of the temperature of the cliche plates (2).

7. Method for speeding up the stamping process in a common hot stamping machine (1) according to the preceding claims wherein all the air supplied by the supply duct (14) to the nozzles (10) is filtered, dehumidified, compressed and heated according to pre-set parameters and constantly monitored by common monitoring means.

8. Method for speeding up the stamping process in a common hot stamping machine (1) according to the preceding claims wherein if the temperature detected by the heat sensors (17) is different from the set parameters, a common alarm system is activated along with an immediate reduction of the stamping speed of the hot stamping machine

(1)^.