METHOD AND MACHINE FOR FRICTION WELDING OF TWO HEAT-SEALABLE FILMS USING A PREHEATED ROTATING TOOL WITH VARIABLE TURN SPEED

Description

TECHNICAL FIELD

[0001] The invention relates to the field of friction heat sealing between two overlapping, multilayer, heat-sealable films, using a rotating tool moved along a predefined trajectory against one of the films. The invention relates to such a friction heat sealing process between two films by thermally sealing the heat-sealable layers of the films applied against each other, and to a numerically controlled machine for implementing this process. STATE OF THE ART

[0002] It is common to create flexible packaging from multilayer films that are layered and joined together by heat sealing. The heat sealing between the films is performed along a weld line of varying width and complexity, depending on the desired packaging.

[0003] The layers of the films comprise an outer layer of varying thickness, flexible or rigid, and an inner layer through which the films are bonded together. For this purpose, the inner layers of the films are heat-sealed, commonly made from a polymer or a sealing varnish; in other words, they are thermally sealed together by heating them to their melting point and then cooling them. The outer layer may be made from a polymer material or any other material that provides support for the inner layer. Such a support material for the inner layer might, for example, be a cellular material potentially coated with a polymer layer, or it could be a composite material, such as one made from cohesive fibers.

[0004] For sealing, the films are placed in layers at a sealing station on a heat-sealing machine, with the inner layers of the films facing each other. The films are typically packaged as a strip wound around a single roller and folded back on itself into two overlapping layers, thus sealing the films together. Alternatively, they are packaged as individual strips wound around a dedicated roller, the roller(s) being mounted on a reel attached to the machine frame. The packages are thus formed successively at the sealing station by the step-by-step advance of separate strips from which the films are drawn, or from a single strip from which the films are drawn by folding the strip back on itself. The sealed films are then cut, and the resulting package is removed from the heat-sealing machine.

[0005] Heat sealing of films is achieved by heating them with a heating tool applied to the outer layer of one of the films. As the films reach a set temperature, their inner layer melts, and subsequently, after cooling, the films fuse together. Heat sealing machines typically include a digital control system that manages the machine and performs various operations to produce the finished package.

[0006] Numerous heat-sealing techniques are used for films. The choice of which of these different heat-sealing techniques to use depends primarily on the desired packaging. The goal is to find the best compromise between various factors, including: ) the materials from which the heat-sealable films are made, in particular the materials from which the outer and inner layers of the films are made respectively, ) the melting temperature of the inner layer of the films without risk of significant degradation of their respective outer layers, ) the more or less complex configuration of the sealing line to be obtained, ) the production rates of the successively obtained packages, and / or ) the methods of parameterization by an operator of the numerical control of the machine to achieve a quality heat seal between the films which conforms to the specifications of the package to be obtained.

[0007] Within the scope of the invention, the technique of friction heat sealing is known, as described, for example, in documents FR3023744-B1 (DELTA COMPOSANTS SA) and FR3023745-B1 (DELTA COMPOSANTS SA). According to this technique, the welding between the films is performed by a rotating tool applied against the outer layer of one of the films covering the other. The rotating tool is moved across the surface of the outer layer of the first film along a predefined path that defines the extent of the weld line between the films. The width of the weld line is defined by the diameter of the contact area of ​​the distal end of the rotating tool against the first film.

[0008] The friction exerted by the rotating tool against the first film generates a temperature increase in the films to a predetermined level depending on the materials from which they are made. This temperature increase enhances the mobility of the polymer chains in the respective internal layers of the films, thus enabling inter-diffusion between these polymer chains and resulting in the films bonding together after cooling.

[0009] To optimize the efficiency of the weld between the films along the weld line, it is known to supplement the friction produced by mixing the films with the rotary tool applied against the first film. Such a friction-stirring heat-sealing technique was, for example, described in document FR3023745-B1 (DELTA COMPOSANTS SA).

[0010] According to this friction stir heat sealing technique, the rotary tool applied against the first film follows a more complex effective path than that defining the weld line obtained between the films. Furthermore, the rotary tool is moved along the weld line with a succession of forward, recoil, and cross-movements.

[0011] This has the effect of generating a mixing of the internal layers of the films together along the effective path of the tool defining the weld line, from a succession of crossings of the displacement of the face of the rotary tool applied against the external layer of the first film.

[0012] In summary, due to the friction of the rotating tool against the first film and its movement along this trajectory—following a path that can be more or less complex, particularly in the case of friction stir welding—the rotating tool heats up. This has the effect of both raising the internal layers of the films to their melting temperature and promoting their inter-diffusion on either side of the welding interface between the films, the resulting weld being generated after the polymer chains solidify through cooling.

[0013] A heat-welding process and the associated machine are also known from the work of Ms. Tannous published in 2022 in the scientific journal "International Journal of Material Forming" Volume 15 Article No. 19, which is relevant to the invention.

[0014] This provides the advantages of allowing the films to be welded together along a potentially complex trajectory - which is adaptable according to the weld line between the films of the packaging to be obtained - and this while limiting production downtime in the event of a change in the trajectory to be followed by the rotary tool according to differentiated packaging to be obtained.

[0015] As a reminder, and if necessary to clarify the concepts and / or related terms used subsequently that are commonly understood by a person skilled in the art of friction heat sealing between heat-sealable films: The films are each multi-layered, with an inner heat-sealing layer integrated into an outer layer that can itself be further sub-layered. This outer layer provides the resulting packaging with its inherent shape retention. The films are held in overlapping layers at the film-sealing station. The outer layer of one film faces a sealing head, while the outer layer of the second film rests on a platform formed by the frame of the film-sealing machine. In other words, the heat-sealable inner layers of the films face each other for sealing, unlike the outer layers, which face outwards from the finished package. The sealing head is equipped with a rotary tool and a drive motor to rotate it.The machine is equipped with a welding head manipulator along the three axes of an orthonormal coordinate system. The rotary tool is moved in contact with the first film along its path in a plane defined by two of these axes, the third axis identifying the axial contact direction of the rotary tool against the outer layer of the first film. DESCRIPTION OF THE INVENTION

[0016] In this context, the invention relates to a friction heat-sealing process between two superimposed heat-sealable films and a numerically controlled machine for implementing said process, notably on a non-exclusive basis for the formation of packaging.

[0017] The films are welded to each other via internal layers which they respectively contain and which are heat-sealable to each other by means of friction operated axially by a face of the distal end of a rotating tool which is applied against an external layer of a first of said films and which progresses along a trajectory which is predefined in a plane and which determines a line of welding of the films together.

[0018] The approach of the invention is based on the observation that the heat sealing technique by friction and / or by friction-mixing between films presents several disadvantages and problems to be solved which are set out below as a non-restrictive guide.

[0019] The friction and / or friction-stir heat sealing technique is largely limited to heat sealing between rigid films, such as those made of PET (polyethylene terephthalate). This consequently restricts the potential application of this technique to other materials from which films could be made, notably by excluding friction heat sealing between films made from other known, more flexible and / or brittle materials, such as PP (polypropylene) or PE (polyethylene).

[0020] Such an exclusion of potential applications to other materials is all the more detrimental as the evolution of techniques tends to develop new materials that are more flexible and / or more fragile, such as sought-after materials that are biodegradable and / or facilitate their recycling, particularly with regard to packaging.

[0021] The friction and / or friction-stir heat welding technique depends on numerous parameters that must be considered to achieve a reliable and high-quality weld between the films. These parameters are primarily related to the materials from which the films are made, the complexity of the path followed by the rotary tool and consequently the suitability of the resulting weld line, and / or the rotational speed of the rotary tool, which generates the frictional heating of the films, leading to the melting of their inner layer.

[0022] However, the values ​​of these various parameters influence the quality of the weld obtained from the machine's operation regulated by the numerical control used for its implementation. Inappropriate consideration of these parameters and / or an insufficient, even arbitrary or subjective, definition of their respective values ​​by an operator tends to affect the quality of the resulting heat weld—particularly regarding the achievement of a homogeneous and reliable weld line—and to complicate the operator's task of programming the numerical control system equipping the machine.

[0023] Such disadvantages tend to make the use of friction heat sealing prohibitive for the formation of packaging that must meet precise and rigorous specifications, and / or for the formation of packaging made from other materials as previously mentioned, to the detriment of the advantages provided by friction heat sealing, particularly with regard to the formation of a weld line between films that may have a complex configuration.

[0024] The movement of the rotary tool along a more or less complex trajectory induces a local variation in its speed of movement along its trajectory.

[0025] This has the effect of affecting the homogeneity of the weld line obtained, or even locally deteriorating the outer layer of the first film against which the rotary tool is applied, particularly in the case of application of the friction stir welding technique.

[0026] This presents an additional challenge in mitigating the consequences—difficult to control—induced by variations in the speed of the rotating tool along its path. These variations can locally cause overheating of the films, which is detrimental to their integrity, or conversely, lead to defective welds between the films. Ideally, the heat generated by the friction of the rotating tool against the first film should remain relatively constant along its path within a predefined temperature range.

[0027] Furthermore, the friction and / or friction-stir heat-sealing technique affects production rates. It follows that the speed of the rotary tool along its path is a determining factor in the time required to produce the package, a time that is even longer when using the friction-stir heat-sealing technique.

[0028] It should therefore be noted that it is desirable to avoid heat sealing films by friction-mixing, as it further complicates the trajectory followed by the rotary tool and increases the risk of degradation of the films, due to successive forward and backward and / or cross movements of the rotary tool along its trajectory delimiting the weld line obtained between the films.

[0029] Another difficulty to overcome is that the film temperature is significantly lower than that of the rotary tool downstream of its position, depending on the direction of the tool's movement along its trajectory. This further induces a temperature variation in the rotary tool, which is cooled by contact with the films as it progresses, potentially affecting the quality and / or homogeneity of the weld line formed between the films.

[0030] Another difficulty to overcome is that, since the rotary tool has an axially rotating surface, its intrinsic temperature varies from its axis of rotation towards its periphery. This further complicates achieving homogeneous heating of the films at a given weld point and consequently is likely to affect the quality of the weld obtained along the weld line, particularly in areas where the direction of the rotary tool changes along its path.

[0031] Based on the observation just presented, one aim of the invention is to propose a method and a numerically controlled machine for friction heat sealing between heat-sealing films which makes it possible to remedy at least the disadvantages, problems and / or difficulties which have just been described.

[0032] Another objective of the invention is to make the technique of friction heat sealing of multilayer films, where at least the respective inner layers of the films to be welded together are heat-sealable to each other, competitive with regard to other known techniques which are more competitive but at the expense of the advantages provided by the friction heat sealing technique.

[0033] Such advantages of the friction heat sealing technique relate in particular to the formation of a weld line between the films which is potentially of complex configuration and / or the possibility of quickly and easily modifying the configuration of the weld line, unlike other known heat sealing techniques which are simpler to implement - such as heat sealing via a heating bar - but which require a specific rearrangement of the welding station according to the packaging to be obtained, which is particularly detrimental in the case of a series production of limited quantities of packaging.

[0034] The invention aims in particular – based on the use of friction heat sealing via a rotating tool moved along a more or less complex trajectory – to enable sealing along a weld line between heat-sealable films which provides at least the following advantages and / or technical results, considered individually or in combination in at least two pairs: ) to obtain a high-quality weld between the films, which is homogeneous and reliable along the weld line sealing the films together. Such a weld line has a configuration that can be more or less complex, potentially including frequent and / or abrupt changes of direction in the overall plane of film overlap. ) to optimize the potential applications of friction heat sealing to films that can be selectively made from many different materials, including, but not limited to, their physicochemical structure, their thermal conductivity – particularly with regard to the outer layer of the films – their rigidity or flexibility, the specifications of the packaging to be obtained, and / or their ability to be biodegradable and / or easily recyclable after the packaging has been used.) To optimize the potential applications of friction heat sealing to multilayer films whose different layers may be made of different materials or of the same material with varying densities and / or thicknesses depending on the layer, without affecting the quality of the seal between the films and / or avoiding significant degradation of their outer layer. ) To improve packaging production rates without affecting the quality and reliability of the seal between the films, nor the possibility of obtaining a complex film sealing line.) To propose a Human-Machine Interface (HMI) that facilitates and simplifies for an operator – including a human operator – the parameter settings of the machine's numerical control regulating the heat-sealing operation, and the control, by the machine's numerical control and / or by the operator, of the heat-sealing process carried out in accordance with the specifications of the packaging to be obtained. ) To ensure the reliability of the rotary tool's movement along its trajectory, providing a homogeneous and high-quality seal between the films – under the control of the machine's numerical control – by facilitating the operator's task of configuring the machine's numerical control for this purpose using objective parameters.) to collect and transmit reliable information to the numerical control system, which is useful for regulating the heat-sealing operation according to a rigorous protocol, preferably while avoiding as much as possible structurally complicating the means implemented for this purpose and without affecting their performance or reliability.

[0035] To this end, and in light of the aforementioned observation relating to the approach of the invention, the invention proposes – under the control of the numerical control – to identify and transmit to a machine control module: ) a setpoint temperature for welding the films together determined according to objective parameters entered by an operator such as the characteristics of the films to be welded, from which the numerical control determines a setpoint rotation speed of the rotary tool to be applied, ) the objective configuration of the trajectory of the rotary tool to be followed in application against said first film, which is entered by an operator and from which the numerical control determines at least a kinematic and a dynamic of putting into mobility of the rotary tool in rotation and along said trajectory, ) prior to the application of the rotary tool against the first film, preheating the rotary tool - via an auxiliary heating means of the rotary tool - to an initial setpoint temperature suitable for causing a start of melting of the inner layer of the films.It is understood that the preheating of the rotary tool is carried out prior to its application against the first film and is interrupted as soon as the welding of the films together begins at the start of the trajectory to be followed by the rotary tool driven at the specified rotational speed. Then, proceed with the friction welding of the films together via the rotary tool, by measuring and transmitting to the numerical control the effective temperature of the rotary tool, measured continuously at the axial contact point between the rotary tool and the first film throughout its trajectory, and adapt via the numerical control, primarily the rotational speed of the rotary tool, taking into account at least the said effective temperature, in order to obtain a substantially constant heating temperature of the films and conforming to the specified welding temperature along the trajectory followed by the rotary tool.

[0036] Such a priority adjustment of the rotary tool's rotational speed may be temporarily insufficient to provide a film heating temperature that meets the setpoint for welding the films together. In such a situation, the rotary tool's auxiliary heating system can be used by being temporarily activated by the numerical control, as long as the actual temperature of the rotary tool, which is continuously measured at the axial contact point between the rotary tool and the first film, is identified by the numerical control as being lower than the setpoint for welding the films together.

[0037] Preheating the rotary tool to the initial set temperature, prior to its application against the first film, allows, in particular: This avoids the initial time required to raise the temperature of the rotary tool against the first film to the set initial temperature through friction at the beginning of the film welding process. This increases the production rate of successive packages. Furthermore, the initial film welding phase eliminates the need for friction and / or kneading of the first film to raise the rotary tool to the welding set temperature. This preserves the quality of the film weld by minimizing cold friction of the rotary tool against the first film during the initial welding phase.) to ensure the films begin to weld together from the very start of the rotary tool's path, guaranteeing a homogeneous, reliable, and high-quality weld line from the outset and throughout the entire path. ) to prevent degradation of the outer layer of the first film by the rotary tool along a segment at the beginning of its path. This degradation would result from the time required for the rotary tool to reach a sufficient temperature to fuse the inner layers of the films through its rotational friction against the first film alone. The homogeneity of the weld line's quality is further reinforced regardless of the material(s) from which the films are made and / or the potentially complex configuration of the weld line to be obtained.) to temporarily compensate for a temperature difference between the actual measured temperature of the rotary tool and the welding setpoint temperature, which would be induced in particular by a variation in the rotational speed of the rotary tool required by the numerical control.

[0038] Adapting the rotary tool's rotational speed via numerical control, based at least on the actual temperature measured in real time at the current weld point—or, in other words, the continuously measured actual temperature at any weld point considered at a given instant along the rotary tool's path—further ensures a homogeneous weld line between the films. Moreover, using this numerical control approach to adapt the rotary tool's rotational speed, values ​​of other parameters can be correlated with the actual temperature to adjust the rotary tool's rotational speed as described below.

[0039] To this end, the invention proposes that the adaptation of the rotation speed of the rotary tool by the numerical control also take into account the diameter of the rotary tool, the dynamics of the rotary tool, and / or locally the intrinsic temperature of the films prior to their progressive heating by the rotary tool along its trajectory, or in other words the intrinsic temperature of the films immediately downstream - following the trajectory followed by the rotary tool - of the axial friction point of the rotary tool against the first film.

[0040] Continuous measurement of the effective temperature of the rotary tool at the axial contact point between the rotary tool and the first film ensures a homogeneous weld of the films along the weld line. This measurement takes into account—depending on the tool diameter—the temperature variation between this axial contact point and the diametrical periphery of the rotary tool. In other words, since the temperature of the rotary tool typically varies between its center and its periphery, the effective temperature of the rotary tool is advantageously measured along its center, defined by its axis of rotation as described later. The welding setpoint temperature is thus determined based on the tool diameter, taking into account the temperature variation between its center and its periphery.

[0041] This ensures that a homogeneous weld is obtained between the films along the entire path followed by the rotary tool, by prioritizing the speed of advancement of the rotary tool along its path notwithstanding a variation in the width of the weld line obtained which would be induced in particular by a change of direction of said path.

[0042] More specifically, regarding the consideration of the dynamics of the rotary tool, this is considered with regard to the speed of movement of the rotary tool along said trajectory and / or with regard to the pressure exerted by the rotary tool against the first film, which are advantageously prioritized at constant value by the numerical control, and this without affecting: ) obtaining a welding temperature in accordance with the welding setpoint temperature along the entire path followed by the tool, including in the event of a change in direction of the path followed by the rotary tool, and / or, ) obtaining a homogeneous weld quality between the films along the weld line by taking into account the diameter of the rotary tool whose application against the films throughout its path is determined by the constant pressure numerical control.

[0043] Prioritizing the speed of movement of the rotary tool and the pressure exerted by the rotary tool against the films following said trajectory allows for prioritizing the speed of movement of the rotary tool and thus increasing the production rates of successive packages.

[0044] This is achieved without affecting the quality of the weld line obtained, by heating the films by friction at a constant temperature in accordance with the welding setpoint temperature, by varying for this purpose primarily the rotation speed of the rotary tool applied against the films - and secondarily as previously referred to by temporarily activating the auxiliary heating means of the rotary tool if necessary in the event of a request for acceleration of the rotary tool - and this taking into account at least the effective temperature of the rotary tool measured axially continuously.

[0045] ByRegarding the intrinsic temperature of the films, the invention proposes interposing a support, preferably flexible, between the second film and the platform of the frame on which the superimposed films are installed. The support is equipped with a heating element—such as a heating plate, for example—to heat the films to a specific temperature threshold.

[0046] The said The temperature threshold is determined by the numerical control based at least on the physicochemical characteristics of the films to limit the amplitude of possible thermal shocks between the rotary tool and the films along the path followed by the rotary tool, and / or to promote homogeneous welding of the films together over the entire weld line obtained.

[0047] This promotes high-quality welding between films that can be made from various materials—including recyclable or biodegradable materials—and / or regardless of ambient conditions during the welding operation. It also facilitates increased packaging production rates by maintaining a constant, prioritized speed of tool movement along its path.

[0048] The heating of the films to the temperature threshold - via said support - is placed under the control of the activation of the heating element by the numerical control during the period of welding the films together, at a temperature threshold of a potentially variable value and calculated by the numerical control as close as possible to the welding setpoint temperature while remaining below the melting temperature of the outer layers of the films.

[0049] This reduces the temperature difference between the current axial contact point of the rotary tool and the axial contact point located downstream of said current axial contact point along the path followed by the rotary tool, and consequently further optimizes the speed of movement of the rotary tool along its path and increases the production rate of the packaging, without affecting the quality and reliability of the weld line obtained in accordance with the specifications of any packaging to be obtained.

[0050] Furthermore, the invention proposes to use a calculation model to determine the values ​​of all the parameters involved in the machine's control of the film welding operation via numerical control. The calculation model is interfaced between an input data device for the operator and at least one module for controlling the machine via numerical control.

[0051] From the input data - which according to the invention are chosen in a limited number at best and whose objective values ​​are easily identified by an operator - the calculation model generates by calculation output data which are then selectively used either directly by the control module or by a module for regulating the preheating temperature of the rotary tool and the variable rotation speed of the rotary tool.

[0052] More specifically, the objective input data entered by the operator and transmitted to the calculation model is limited, at least to: ) the first input data relating to the material from which the layers composing the films to be welded are respectively derived, the thickness of the films or at least that of the outer layer of the first film against which the rotary tool is intended to be applied, and the diameter of the rotary tool. ) the second input data relating to the trajectory to be followed by the rotary tool in application against the outer layer of the first film, in particular by identifying the position of nodes of the trajectory indicating a change of direction of the progression of the tool and / or by identifying the geometry of at least one segment of the trajectory between successive nodes.

[0053] Based on the objective input data entered by the operator – that is, excluding all estimated or calculated data by the human operator – the calculation model determines output data relating at least to: ) a welding setpoint temperature, corresponding to the temperature to be reached by the rotary tool at the point of contact against the outer layer of the first film, and a nominal rotation speed of the rotary tool to be applied to heat the outer layer of the first film to a temperature providing fusion of the inner layers of the films, ) the pressure to be exerted - preferably at a constant value - by the rotary tool against the outer layer of the first film, and ) the path to be followed by the rotary tool at an optimized travel speed - preferably at a constant value - of the rotary tool along its path.

[0054] The control module directly uses the continuously provided output data from the calculation model, which relates to the trajectory to be followed by the rotary tool, the pressure to be exerted by the rotary tool against the outer layer of the first film along its trajectory, and the speed of movement of the rotary tool along its trajectory. Such output data is therefore prioritized.

[0055] Furthermore, the regulation module – interfaced between the calculation model and the control module – regulates: ) the initial preheating setpoint temperature of the rotary tool to be applied, at least from the welding setpoint temperature, and ) the effective rotational speed of the rotary tool to be applied along its path, which is potentially variable – from the welding setpoint temperature and the nominal rotational speed of the rotary tool to be applied. The effective rotational speed of the rotary tool to be applied is corrected by the control module based on the effective temperature of the rotary tool, measured continuously along its path, axially at the center of its flat application face against the first film.

[0056] The intrinsic temperature of the films outside the area of ​​contact of the rotary tool against the first film is potentially taken into account by the downstream numerical control – depending on the direction of movement of the rotary tool along its trajectory – of the current contact area of ​​the rotary tool against the first film, from: ) taking into account the ambient temperature at the welding station measured via an auxiliary temperature probe, preferably as close as possible to the outer layer of the first film or even in contact with the outer layer of the first film outside the area of ​​the first film located within the perimeter of the trajectory followed by the rotary tool, and / or ) where appropriate from the heating temperature of said support which is controlled by the regulation module according to the conditions which have been stated.

[0057] The initial setpoint temperature and the effective rotational speed of the rotary tool are preferably regulated by separate controllers within the control module, based on output data generated by the computer and transmitted to the control module. The values ​​calculated by the calculation model and by the various controllers within the control module are iteratively calculated and correlated to identify the limits of the heat-sealing range to be performed.

[0058] The area of ​​heat sealing to be carried out is thus defined by the values ​​of the different parameters to be taken into account along the entire trajectory followed by the rotary tool, which are identified by the calculation model from the input data and which are selectively either processed by the regulation module or directly transmitted to the control module as previously mentioned.

[0059] More specifically, the field of heat sealing is bounded by limits that fall within at least: ) the maximum value of the initial setpoint temperature, ) the maximum value of the temperature of the rotary tool applied under constant prioritized pressure against the outer layer of the first film. The constant pressure applied by the rotary tool against the first film limits its degradation and / or prevents variations in shape along the seal line of the resulting package, ) the range of permissible values ​​of the rotary tool's rotational speed, which varies along the rotary tool's path as a function of the effective temperature of the rotary tool measured continuously along its path axially, ) the prioritized value of the optimized rotary tool's travel speed along the path, and the value of the pressure – prioritized at a constant value – applied by the rotary tool against the outer layer of the first film.

[0060] The invention also provides a numerically controlled machine for heat-sealing said films together by friction, in accordance with the process of the invention just described. The machine comprises at least: ) a welding head which is equipped with said rotary tool, the proximal end of the rotary tool having a drive shaft rotated by a motor mounted on the welding head, the distal end of the rotary tool being oriented towards the films to be welded together, and ) a manipulator for moving the welding head along the three axes of an orthonormal frame, the rotary tool being applied along any one of the axes by the manipulator against the outer face of said first film and being moved along its trajectory along a plane defined by the other two axes of said orthonormal frame.

[0061] Atless the implementation of the motor drive for rotating the rotary tool and the manipulator moving the welding head – including, in particular, applying the rotary tool against the films and moving it along its trajectory are placed under the dependence of command orders generated by a control module under the control of the numerical control, the implementation of which is placed under the dependence of instructions generated by a calculation system from the entry of objective input data by an operator.

[0062] The rotary tool is equipped with: ) of said auxiliary heating means - being understood as complementary to the friction heating of the rotary tool applied against the outer layer of the first film - the activation of which is regulated by the numerical control, in particular via the regulation module, ) of a temperature sensor which extends inside a channel formed axially inside the rotary tool, equipped at its distal end with a temperature probe which is placed inside the channel near the distal end of the rotary tool at its center identified by its axis of rotation.

[0063] The welding head is equipped with an electronic circuit board that is advantageously energy self-sufficient, thanks in particular to an energy reserve it carries. The electronic circuit board: ) collects information relating at least to temperature data detected by said temperature sensor and to information on the rotational dynamics of the rotary tool detected, for example, by an accelerometer fitted to the welding head. The accelerometer may, in particular, be installed on the rotary tool, on a motorized shaft for rotating the rotary tool, or on the motor for rotating said shaft, ) is equipped with a device for transmitting / receiving information waves, which may also, in a variant, be installed on the frame of the welding head - via which the information collected by the electronic board can be transmitted at least to the numerical control fitting the machine.

[0064] The electronic board is preferably installed on the drive shaft, with its proximal end protruding from the motor, opposite its proximal end through which the rotary tool is driven. To clarify the relative terms proximal and distal as applied to the structural definition of the rotary tool and the welding head and / or its equipment, the distal end of the rotary tool is oriented towards the films and its proximal end towards the motor that drives its rotation.

[0065] Such an arrangement of the welding head and its equipment allows, using simple and compact structural means: ) to easily and continuously control at least the effective temperature of the rotary tool at the axial contact point against the outer layer of the first film and / or the effective rotation speed of the rotary tool, and ) to transmit it to the numerical control which controls - from at least the objective data transmitted by the electronic card - the heat-sealing operation of the films in accordance with the protocol as just described according to the process relating to the invention.

[0066] The auxiliary heating means advantageously consists of a metallic body with a very low coefficient of expansion which comprises the rotating tool at its distal end intended to be applied against the outer layer of the first film, and an induction heating device for said metallic body.

[0067] Additionally, a vibration detector installed on the welding head can identify any rotational imbalance of the rotary tool. Such imbalance should be avoided and is likely to compromise the integrity of the weld line between the films and / or the uniformity of the heat transferred by friction to the outer layer of the first film. If such an imbalance is detected at a predefined vibration threshold, an alert signal can be generated based on information collected and transmitted by the electronic board to an audible and / or visual alarm generator, for example.

[0068] The numerical control of the heat-sealing machine is equipped with an input device for operator use and a calculation system comprising at least one calculation model and one control module. The calculation system is interfaced between the input device and the machine control module of the numerical control. The calculation model is interfaced between the input device and the control module.

[0069] At As stated above, the invention relates to a friction heat-sealing process using a rotary tool between two superimposed heat-sealing films, comprising a first film and a second film. Each film has an outer and an inner heat-sealing layer.

[0070] According to such a process: The films are installed superimposed on a platform equipped with a CNC friction heat-sealing machine. The inner layers of the films are oriented towards each other in the heat-sealing position. The outer layer of the second film faces the platform, and the outer layer of the first film faces a welding head that carries the rotary tool and a drive motor for its rotation. An operator inputs data relating at least to the structural characteristics of the films and a trajectory to be followed by the rotary tool in axial contact with the outer layer of the first film.

[0071] From the said input data and dependent on instruction data transmitted by the numerical control to a control module, the control module - including at least one control module for the implementation of the welding head - generates control orders relating at least to a drive of the rotary tool at a set rotation speed, and to a movement of the welding head according to a kinematic and dynamic movement of the rotary tool along said trajectory, in accordance with obtaining a set temperature for welding the films together.

[0072] In this context, according to the invention, such a process comprises at least the following operations: ) prior to applying the rotary tool against the first film and under the control of a calculation system equipping the numerical control, preheat the rotary tool by an auxiliary heating means.The rotary tool is preheated to an initial setpoint temperature – identified by the calculation system – suitable for initiating fusion of the inner layer of the films. Then, with the preheating of the rotary tool interrupted, friction welding of the films together via the rotary tool is carried out, measuring and transmitting to said calculation system the effective temperature continuously measured at the axial contact point against the first film of the rotary tool along its trajectory. The rotation speed of the rotary tool is then regulated via said calculation system, taking into account at least said effective measured temperature, in accordance with obtaining, along said trajectory, a heating temperature of the films conforming to said welding setpoint temperature.

[0073] It is understood that: ) the rotational speed of the rotary tool is regulated at a variable speed along the path followed by the rotary tool, as a function at least of said effective temperature of the rotary tool measured axially at its center at said axial contact point against the first film, and this in accordance with maintaining by friction the substantially constant temperature of the rotary tool at the welding setpoint temperature, and ) The rotary tool is preheated to the initial setpoint temperature prior to its application against the first film, then the rotational speed of the rotary tool is regulated by the calculation system according to the welding setpoint temperature to be reached by friction of the rotary tool against the outer layer of the first film, from at least said continuous measurement of the rotary tool at the axial contact point of the rotary tool against the first film,

[0074] Of theSpecific features and additional characteristics of a process relating to the invention are set out below.

[0075] The regulation of the rotary tool's rotational speed by the calculation system also takes into account at least one of the following parameters: ) the diameter of the rotary tool, ) the dynamics of the rotary tool's rotation, as a function of the speed of movement of the rotary tool along said trajectory and the pressure exerted by the rotary tool against the first film, ) the intrinsic temperature of the films measured continuously at the axial contact point of the rotary tool against the first film, via the temperature sensor with which it is equipped as referred to later.

[0076] The respective values ​​of the rotary tool's travel speed along the trajectory and the pressure exerted by the rotary tool against the outer layer of the first film are prioritized at constant values. The film welding temperature is adjusted by varying the rotary tool's rotation speed to achieve the set welding temperature, which is maintained constant throughout the entire trajectory of the rotary tool.

[0077] It is understood - as previously referred to - that marginally following a controlled variation of the rotation speed of the rotary tool - in particular in acceleration - the auxiliary heating means normally inactivated during the welding operation, may be temporarily activated by the calculation system during the welding operation to compensate in this case for a deficiency in temperature rise of the rotary tool.

[0078] Such a deficiency in the rotary tool's temperature rise is identified by the calculation system based on the effective temperature, continuously measured at the axial contact point between the first film and the rotary tool along its trajectory. This temperature is then continuously compared, for example, to a range of permissible rotary tool temperatures. From this comparison, the calculation system identifies an insufficient temperature rise in the rotary tool and, in such cases, triggers a temporary activation of the auxiliary heating element.

[0079] The process involves – during the film welding phase and under the control of the computing system – heating a support placed between the second film and the platform on which the superimposed films rest. The heated support raises the temperature of the superimposed films to a threshold temperature whose maximum value is as close as possible to the welding setpoint temperature while remaining below the melting temperature of the outer layers of the films.

[0080] In other words, the difference between, on the one hand, the temperature of the outer layer of the first film at the axial contact point - also called the axial friction point - of the rotating tool applied against it and, on the other hand, the intrinsic temperature of the films resulting from their heating by the support is minimized at best.

[0081] AThe calculation model implemented by a computer within the calculation system determines output data from the input data. The input data includes at least the diameter of the rotary tool. The output data includes at least the path to be followed by the rotary tool, the speed of movement of the rotary tool, the pressure exerted by the rotary tool against the first film, a nominal rotational speed of the rotary tool, and the setpoint temperature for welding the films together.

[0082] At The output data relating to the rotary tool's travel speed and the pressure exerted by the rotary tool against the first film are prioritized by being directly transmitted to and processed by the control module. The calculation system regulates, via a control module it contains, the following values ​​transmitted to the control module: ) said initial setpoint temperature from at least the output data relating to the welding setpoint temperature, and ) the effective rotational speed of the rotary tool to be applied by the control module, from the output data relating to the nominal rotational speed of the rotary tool, the output data relating to the welding setpoint temperature and the effective temperature of the rotary tool measured continuously at the axial contact point between the first film and the rotary tool along its path.

[0083] It is further specified and understood that the axial contact point between the rotary tool and the first film is identified as the contact point of the rotary tool located along its axis of extension at the center of the flat end face of the rotary tool that is applied against the first film. This, as explained later, is due to the presence of the temperature sensor, which is housed inside the axial channel extending within the rotary tool, and whose temperature probe is positioned near the flat end face of the rotary tool.

[0084] The temperature threshold of the superimposed films heated via the substrate is calculated by a processing unit based on the output data relating to the welding setpoint temperature. This calculated temperature threshold, being lower than the welding setpoint temperature, is then transmitted by a control module that activates a heating element for the substrate.

[0085] The input data relates at least to the materials from which the films are respectively derived, the thickness of the films, the diameter of the rotary tool, and the trajectory to be followed by the rotary tool.

[0086] Such input data is thus limited to objectively valued data entered by a human operator. In other words, the input data is limited to objective data that excludes any subjectivity on the part of the operator, nor requires the operator to perform any calculations or refer to a chart—or any other similar tool—prior to entry, thereby simplifying the operator's task when entering the input data.

[0087] It is also understood that the layers of at least one of the films may be made from different materials or from the same material, the layers in the latter case being able to be differentiated according to their thickness and / or their density for example.

[0088] The output data from the calculation performed by the calculation model relates at least to the trajectory to be followed by the rotary tool, the welding setpoint temperature, a nominal rotation speed of the rotary tool, the pressure to be exerted against the outer layer of the first film by the rotary tool along its trajectory and an optimized movement speed of the rotary tool along its trajectory.

[0089] The control module regulates at least: ) the initial setpoint temperature to be applied, derived from the welding setpoint temperature and the temperature difference of the outer layer of the first film between the current axial contact point of the rotary tool and a downstream axial contact point of the rotary tool along its path, and ) the effective rotational speed of the rotary tool to be applied, derived from the welding setpoint temperature and the nominal rotational speed of the rotary tool. The regulation of the effective rotational speed of the rotary tool is corrected by the calculation system equipping the numerical control, at least as a function of the effective temperature of the rotary tool measured continuously at the axial contact point between the first film and the rotary tool along its path.

[0090] The output data from the calculation performed by the model, on the one hand, and the adjustments made by the control module, on the other, are iteratively calculated and correlated to identify the limits of the welding range. The welding range is defined as the permissible range of values ​​that determine the machine's operating parameters to be applied by the control module to perform the heat sealing between the films.

[0091] The invention also relates to a numerically controlled machine for friction heat sealing via a rotating tool between two superimposed heat-sealing films. The numerically controlled machine of the invention is designed to implement a heat sealing process as described above.

[0092] The machine is of the type least equipped: ) of a said installation platform for said superimposed films, ) of a said welding head carrying the rotary tool and of a said motorization for rotating the rotary tool, ) of a said manipulator for moving the welding head along the three axes of an orthonormal frame, two axes of which define a plane for superimposing the films and the third axis of which defines the axial application direction of the rotary tool against the superimposed films, ) of said numerical control at least equipped with a said input device for an operator to input said data, of said calculation system generating instructions from the input data used by a said control module which generates said control orders relating at least to a rotation of the rotary tool at a said set rotation speed and to a said movement of the welding head.

[0093] The movement of the welding head is controlled in particular by the control module according to a kinematic and dynamic movement of the rotary tool following a predefined trajectory, in accordance with obtaining at least a said setpoint welding temperature of the films together being included along the trajectory followed by the rotary tool applied against the first film.

[0094] In this context, according to a machine conforming to the invention, the machine is equipped: ) of an auxiliary heating means for the rotary tool at the initial setpoint temperature, the activation of which is regulated by the computer system equipping the numerical control. The auxiliary heating means is advantageously of the induction type, heating a metallic body of the rotary tool at its distal end, through which the rotary tool is applied against the outer layer of the first film. ) of a temperature sensor disposed inside an axial channel of the rotary tool, the distal end of the temperature sensor being located inside the channel near the end face of the rotary tool through which the rotary tool is applied axially against the outer layer of the first film.

[0095] This machine also features a computing system configured to: Prior to applying the rotary tool against the first film, preheat the rotary tool by the auxiliary heating means to an initial setpoint temperature suitable for causing a start of melting of the inner layer (5b, 6b) of the films, then interrupt the preheating of the rotary tool, and, during the friction welding of the films together via the rotary tool, regulate the rotation speed of the rotary tool (9) taking into account at least one effective measured temperature, in accordance with obtaining along said trajectory a heating temperature of the films conforming to said welding setpoint temperature, the effective temperature corresponding to a temperature measured continuously at the axial contact point against the first film of the rotary tool along the following of its trajectory.

[0096] Additional specific features and characteristics of a machine relating to the invention are set out below.

[0097] The welding head is equipped with an electronic circuit board for collecting information relating at least to the temperature detected by the temperature sensor and the rotational dynamics of the rotary tool detected by an accelerometer. The electronic circuit board is equipped with at least one wireless communication device through which it transmits the collected information to the processing system.

[0098] The auxiliary heating means consists of a metal body, which is part of the rotating tool at its distal end of axial application against the first film, and a heating device for the metal body, which is mounted on the welding head. The heating device is advantageously of the electromagnetic induction heating type, using an inductive coil surrounding the metal body at a short radial distance.

[0099] The metal body is preferably made of a material with a very low coefficient of expansion, such as preferably an iron-nickel alloy (INVAR). The metal body is mounted at the distal end of a proximal body of the rotary tool, which is preferably made of a thermally insulating material, such as polyetheretherketone (PEEK).

[0100] The machine is equipped with an interposition support between the platter and the second film, through which the superimposed films are supported by the platter. The support, preferably flexible, is equipped with a heating element, the activation of which by the control module is controlled by the computer system of the digital control.

[0101] The calculation system includes a calculator for implementing the calculation model. The calculator is interfaced between the input device and the control module included in the calculation system.

[0102] The control module consists of at least two separate controllers, including: ) a first regulator determining the initial setpoint temperature of the auxiliary heating means of the rotary tool from the welding setpoint temperature, and ) a second regulator of the effective rotation speed of the rotary tool to be applied, from said nominal rotation speed, the welding setpoint temperature and said effective temperature of the rotary tool measured continuously by the temperature sensor with which it is equipped.

[0103] The welding head is potentially equipped with a vibration sensor to which the rotary tool is subjected. The activation of an alarm signal generator is dependent on the vibration sensor, being calibrated to a predefined threshold of the maximum tolerated frequency and / or amplitude of the vibrations measured by the vibration sensor.

[0104] At less the vibration sensor and / or subsidiarily the alert generator may be mounted on said electronic card, said generated alert being able to be transmitted by waves via the electronic card to an alert emitting device equipping the machine. PRESENTATION OF THE FIGURES

[0105] The invention will be better understood upon reading the following detailed description of an example embodiment of the invention, in relation to the following figures in the attached plates: ) there figure 1 (FIG.1 Figure 1) is a schematic representation of a numerically controlled friction heat-sealing machine between two superimposed films, according to the present invention, which is illustrated and briefly commented on to present the context of the invention. figure 2 (FIG.2Figure 1) is a schematic axial cross-sectional illustration of an example of a rotary tool according to the invention, equipping a friction heat-sealing machine between two superimposed heat-sealing films according to the invention. figure 2 The rotary tool is shown in the position of application against an outer layer of one of the films – referred to as the first – and the methods of its implementation are schematically illustrated. figure 3 (FIG.3 ) is a logical diagram synthetically illustrating an example of the overall implementation of a friction heat-sealing process between two heat-sealing films according to the invention. It is essentially illustrated on the figure 3 the implementation methods of a numerically controlled machine according to the invention, to perform friction heat sealing between two said heat-sealing films. DETAILED DESCRIPTION

[0106] The figures and their detailed, non-limiting description set forth the invention in particular ways which are not restrictive as to the scope of the invention.

[0107] The figures and their detailed descriptions can help to better understand and define the invention, if necessary in relation to the general description just provided. Furthermore, to avoid cluttering the figures and thus facilitate their reading, the reference numbers assigned to the terms and / or concepts used to describe the invention and indicated on any one of the figures may be repeated in the description of any other figure without implying their presence on all figures.

[0108] On the figure 1A schematic and synthetic representation illustrates an example of a numerically controlled machine 1 2 organized to successively form packages step by step. Machine 1 extends along the three axes X, Y, and Z of an orthonormal coordinate system, comprising a longitudinal axis X, a transverse axis Y, and a vertical axis Z. In the illustrated example, machine 1 is equipped with a platform 3 extending along the longitudinal axis X and the transverse axis Y, and is surmounted by a welding head 4 along the vertical axis Z.

[0109] It is understood that the extension of the platen 3 along the longitudinal / transverse X / Y plane and the orientation of the welding head 4 relative to the platen 3 along the vertical Z axis are mentioned by way of example. Within the scope of the invention, the axes defining the extension plane of the platen 3 and, consequently, the orientation axis of the welding head 4 relative to the platen 3, can be oriented differently according to any orthonormal coordinate system. The packages are formed by friction heat sealing between two multilayer heat-sealable films 5, 6 which are held superimposed and applied against each other on the platen 3.

[0110] By also referring to the figure 2, a first film 5 is oriented towards the welding head 4 and a second film 6 is oriented towards the platen 3. The films 5,6 each have at least two layers 5a,5b; 6a,6b, including an outer layer 5a, 6a and an inner layer 5b, 6b that is heat-sealing and fusible at a specific temperature, the inner layers 5b,6b of the films 5,6 being oriented in application against each other.

[0111] On the figure 1 The films 5,6, for example, come from a strip 56 packaged in a roll installed on a reel 7 to allow step-by-step unwinding of the strip 56 along the plate 3. The strip 56 is folded over itself into two sides, enclosing the films 5,6 respectively. The films 5,6 are then fixed on the plate 3 in an overlapping position for welding to each other via the welding head 4. After the films 5,6 have been welded together, they are conveyed to a cutting station 8 for the resulting package.

[0112] The fusion of the inner layers 5b, 6b of the films 5, 6 is induced by friction exerted by a rotary tool 9 mounted on the welding head 4. The welding head 4 is moved – under the control of the numerical control 2 – along the three axes X, Y, Z of the said orthonormal coordinate system. The rotary tool 9 is thus applied along the Z axis against the outer layer 5a of the first film 5 – as illustrated in the figure 2 - and progresses in application against the first film 5 along the X and / or Y axes along a predefined trajectory TJ1 defining the configuration of the weld line to be obtained between films 5,6.

[0113] As a result of the melting of the inner layers 5b, 6b of the 5,6 films, cooling of the 5,6 films causes them to fuse together. As a reminder, heating the 5,6 films causes the melting of their inner layer 5b, 6b and consequently the inter-diffusion of the polymer chains in the inner layers 5b, 6b of the 5,6 films. Cooling of the 5,6 films then causes the inter-diffused polymer chains to solidify, such as through crystallization in the case of semi-crystalline polymers.

[0114] To do this on the figure 1 and more details on the figure 2 and the figure 3 As discussed further below, the numerical control 2 of machine 1 is generally at least equipped with: ) of an input data capture device 10 for input data DE1 by an operator, ) of a calculation system 11 identifying - from the input data DE1 previously entered by an operator - instructions for moving the welding head 4 and of implementing a motorization 14 for rotating the rotary tool 9.

[0115] A control module 12 generates - from the said instructions identified by the calculation system 11 - control orders OC1 of a manipulator 13 at least relating to the displacement DP1 of the welding head 4 along the three axes X,Y,Z of said orthonormal frame and control orders AC2 at least relating to the regulation of the motorization 14 of rotation drive of the rotary tool 9 with which the welding head 4 is equipped.

[0116] On the figure 2The rotary tool 9 extends axially A1 between a proximal end 9a of the rotary tool 9 coupled to a drive shaft 15 rotatable by said motor 14, and a distal end 9b of the rotary tool 9 whose end face 9c – of planar configuration – is intended to be applied against the outer layer 5a of the first film 5. The rotary tool 9 is composed of at least two bodies, of which: ) a proximal body 16a made of a thermally insulating material, which is coupled at its proximal end 9a to said drive shaft 15 for rotating the rotary tool providing by friction the heat sealing of the films 5,6 via their respective inner layers 5b,6b, and ) a metallic body 16b made of a material with a very low coefficient of expansion, which is mounted on the proximal body 16a at the distal end 9b of the rotary tool 9, said metallic body 16b constituting the rotary tool 9 being applied at its end face 9c against the outer layer 5a of the first film 5.

[0117] The metal body 16b and a heating device 17 for electromagnetic induction of the metal body 16b together form an auxiliary heating means 16b,17 for the rotary tool 9 at its distal end 9b. The heating device 17 combines an inductive coil 17a that generates an electromagnetic field around the metal body 16b and an activation member 17b for the induction coil 17a that supplies it with electric current for this purpose.

[0118] Referring also to the figure 3 , the electrical current supply to the inductive coil 17a by the activation member 17b is selectively operated via the control module 12 under the control of the calculation system 11 which comprises the numerical control 2. The heating device 17 is advantageously installed on the welding head 4, the inductive coil 17a surrounding the metal body 16b.

[0119] Activating the heating device 17 raises the temperature of the metallic body 16b, which constitutes the rotary tool 9, to an initial setpoint temperature T1 calculated by the calculation system 11 of the numerical control 2 of the machine 1, thereby melting the internal layers 5b, 6b of the films 5, 6 as described below. The rotary tool 9 is also equipped with a temperature sensor 18 extending inside an axial channel 19 A1 of the rotary tool 9, said channel 19 preferably being blind at the distal end 18b of the rotary tool 9.

[0120] The temperature sensor 18 extends inside the metal body 16b to near the flat end face 9c of application of the rotary tool 9 - via the metal body 16b which it comprises - against said outer layer 5a of the first film 5. A temperature probe 18c equipping the temperature sensor 18 is in particular disposed in the blind bottom of the channel 19.

[0121] An electronic control board 20 is mounted on the rotating drive shaft 15 of the rotary tool 9, at its proximal end 15a, which protrudes from the drive motor 14 of the rotating drive shaft 15, as illustrated. This electronic control board 20 collects information relating at least to the effective temperature T2 of the rotary tool 9 detected by the temperature sensor 18, to the rotational dynamics of the rotary tool 9 detected by an accelerometer 21, and, secondarily, to any rotational imbalance of the rotary tool 9 detected by a vibration sensor 22. In the illustrated example, the accelerometer 21 and the vibration sensor 22 are installed on the electronic control board 20, but can also—according to alternative embodiments—be installed on the drive motor 14 of the rotating tool 9 or its drive shaft 15.

[0122] The electronic card 20 is also equipped with a communication device 23 by waves through which the electronic card 20 at least transmits to the computing system 11 the information collected by the electronic card 20, and may also potentially receive information transmitted by a transmitter equipping the digital control 2. The electronic card 20 is also equipped with an autonomous energy reserve 24 for its operation.

[0123] Furthermore, on the figure 2 and the figure 3 A support 25 is interposed between the plate 3 and the outer layer 6a of the second film 6. The support 25 is equipped with a heating element 26, the activation of which by the control module 12 is dependent on the calculation system 11 equipping the digital control 2, as detailed below in relation to the figure 3 .

[0124] On the figure 3The numerical control 2 equipping machine 1 includes said input device 10 for input data DE1 by an operator, which is transmitted to a computer 27 included in said calculation system 11. The computer 27 then generates - from the input data DE1 transmitted to it - output data DS1 relating to instructions for executing the heat-sealing operation of the films 5,6 by machine 1. The output data DS1 results from the processing of the input data DE1 by a calculation model 27a implemented by the computer 27.

[0125] According to The DS1 output data generated by the computer 27 and the methods of its use by the numerical control 2, the DS1 output data are transmitted selectively to the control module 12: ) either directly to the control module 12 for a first group of output data DS1 from which the control module 12 then generates the control orders OC1 controlling the manipulator 13 of the welding head 4, ) or indirectly to the control module 12 for a second group of output data DS1, which are transmitted to the control module 12 after their processing by the regulation module 28.

[0126] More specifically, the control module 12 generates at least the following OC1 commands: ) for said first group of output data DS1 identified by the calculator 27 via the calculation model 27a, the displacement DP1 of the rotary tool 9 by the manipulator 13 of the welding head 4 along the X, Y, Z axes of the orthonormal frame. Said first group of output data DS1 includes in particular a data relating to the application at constant pressure P1 along the Z axis of the rotary tool 9 against the outer layer 5a of the first film 5, a data relating to the trajectory TJ1 to be followed by the rotary tool 9 in application against the outer layer 5a of the first film 5 during the welding operation, and data relating to the kinematics and the displacement velocity VD1 - which is prioritized, optimized and constant value - of the rotary tool 9 along the X,Y axes along the trajectory TJ1 to be followed in application against the outer layer 5a of the first film 5, and ) for said second group of output data DS1 identified by the control module 28,data relating to the activation AC1 of the heating device 17 to heat the metal body 16b to the initial setpoint temperature T1 prior to its application against the first film 5 - and / or marginally in the event of a potential insufficient temperature rise of the rotary tool 9 during the welding operation as previously mentioned - and data relating to the activation AC2 of the motor 14 for rotating the rotary tool 9 to an effective rotational speed VN1, potentially variable as detailed later.

[0127] Alternatively, if applicable, the OC1 command commands generated by the control module 12 also include: ) an AC3 activation at a temperature threshold S1 of the heating element 26 equipping the support 25 on which the second film 6 rests, the maximum value of which is determined by a calculation element 29 as close as possible to an output data DS1 relating to a welding setpoint temperature T3 between the films 5, 6 - generated by the computer 27 via the calculation module 27a - provided that it is less than the melting temperature of the outer layers 5a,6a of the films 5,6, ) an AC4 activation of a generator 30 of an alert signal 30a - visual and / or audible for example - of an excessive imbalance of the rotary tool 9.Such excessive imbalance is identified by said generator 30 of an alert signal 30a from a comparison between on the one hand an imbalance information IB1 generated by the vibration sensor 22 and transmitted by the electronic board 20 to the generator 30 of an alert signal 30a, and on the other hand a predefined tolerated threshold S2 of the maximum permissible frequency and / or amplitude(s) of the measured vibrations 22.

[0128] More specifically, the input data DE1 transmitted to the calculator 27 and processed by the calculation model 27a are at least relative: ) to the trajectory TJ1 to be followed by the rotary tool 9, ) to the diameter D1 of the rotary tool 9 considered at the face 9c of the flat end of its distal end 9b intended to be applied against the outer layer 5a of the first film 5, ) to the thickness EP1 of the layers 5a, 5b; 6a, 6b of the films 5, 6 and to the materials M1 from which they are respectively derived, which are determining the physicochemical characteristics of the layers 5a, 5b; 6a, 6b of the films 5, 6. Such input data EP1, M1 are determining in particular with regard to the melting temperature of the inner layers 5b, 6b of the films 5, 6 and the thermal conductivity and / or resistance of the outer layers 5a, 6a of the films 5, 6 to the friction exerted under pressure P1 by the rotary tool 9, in particular concerning the outer layer 5a of the first film 5.

[0129] The input data DE1 is transmitted to the computer 27, which more specifically generates - via the calculation model 27a - the following output data DS1 which are notably distributed into groups of output data DS1 according to selectively their direct use by the control module 12 to generate the control orders OC1, or their prior regulation by the regulation module 28 as previously referred to: ) a first set of prioritized DS1 output data are directly transmitted to the control module 12, including the trajectory TJ1 to be followed by the rotary tool 9 in application against the outer layer 5a of the first film 5, the travel speed VD1 of the rotary tool 9 along its trajectory TJ1 - optimized at constant value - and the pressure P1 exerted at constant value by the rotary tool 9 against the outer layer 5a of the first film 5, and ) a second set of DS1 output data are transmitted to the control module 28, including a nominal rotation speed VN2 of the rotary tool 9 and a welding setpoint temperature T3 of the films 5,6 between them.

[0130] The control module 28 is subdivided into two separate controllers 28a, 28b, of which: ) a first regulator 28a for activating the auxiliary heating means 16b,17 of the rotary tool 9 to said initial setpoint temperature T1, from the welding setpoint temperature T3, and ) a second regulator 28b of the effective rotation speed VN1 of the rotary tool 9 to be applied by the control module 12, from at least the nominal rotation speed VN2 of the rotary tool 9, the welding setpoint temperature T3 of the films 5,6 between them and the effective temperature T2 of the rotary tool 9 measured continuously by the temperature sensor 18.

[0131] By continuation of the OC1 command orders generated by the control module 12 to perform the heat-sealing operation between films 5, 6: ) the rotary tool 9 is heated to the initial setpoint temperature T1 identified by the control module 28 - in particular the first regulator 28a - by activation AC1 via the control module 12 of the auxiliary heating means 16b, 17 of the rotary tool 9, then ) the rotary tool 9 is driven into rotation by activation AC2 via the control module 12 of said motorization 14 at the effective rotation speed VN1 to be applied which is identified by the control module 28, in particular via the second regulator 28b.The rotary tool 9 is then applied against the first film 5 at the beginning of the trajectory TJ1 to be followed by the rotary tool 9, at a pressure P1 identified by the computer 27 via the calculation model 27a, then the rotary tool 9 is driven by the welding head 4 whose kinematics and dynamics are controlled under the control of the control module 12, following its trajectory TJ1 in accordance with the speed of movement VD1 identified by the computer 27 via the calculation model 27a.

[0132] Throughout the trajectory TJ1 followed by the rotary tool 9, the temperature of the rotary tool 9 is continuously measured by the temperature sensor 18. The temperature of the rotary tool 9 is kept substantially constant by exploiting, if necessary, a variation in the rotational speed of the rotary tool 9 in accordance with the effective rotational speed VN1 of the rotary tool 9 which is continuously identified by the control module 28, in particular via the second controller 28b.

[0133] AThe variation of the effective rotational speed VN1 of the rotary tool 9 is possibly controlled as a function of an insufficiency of the effective temperature T2 of the rotary tool 9 measured continuously by the temperature sensor 18. Such an insufficiency of temperature is identified by the temperature sensor 18 at the center of the end face 9c of the rotary tool, to increase its relevance taking into account the temperature difference of the rotary tool 9 between its center and its periphery.

[0134] The effective temperature T2 of the rotary tool 9 may, for example, vary along its trajectory as a result of: ) of a contact of the rotary tool 9 against the first film 5 - at a downstream axial contact point colder than an upstream axial contact point following the direction of progression of the rotary tool 9 along its trajectory TJ1, ) of a change of direction of the rotary tool 9 along its trajectory TJ1, especially if such a change of direction is significant, and / or ) of a possible overheating of the rotary tool 9.

[0135] In such a case of variation of the effective temperature T2 of the rotary tool 9, such variation is ephemeral as it is immediately corrected by the control module 28 - in particular via the second regulator 28b - which consequently regulates the effective rotation speed VN1 of the rotary tool 9 with the effect of quickly restoring the temperature of the rotary tool 9 in accordance with the welding setpoint temperature T3 identified by the computer 27.

[0136] The effective temperature T2 of the rotary tool 9 is thus maintained substantially constant throughout its trajectory TJ1 by varying the effective rotational speed VN1 of the rotary tool 9 and, if necessary, by temporarily activating the auxiliary heating means 16b, 17 of the rotary tool as previously described. The application of the rotary tool 9 against the first film 5 at its distal end 9b via the flat end face 9c of the metal body 16b is carried out at a pressure P1 exerted by the rotary tool 9 against the outer layer 5a of the first film 5, which can be moderated and controlled at a constant value by the calculation system 11.

[0137] Packaging production rates are improved by prioritizing the travel speed VD1 of the rotary tool 9 along its path TJ1, and by maintaining a constant effective temperature T2 of the rotary tool 9 throughout its path. The resulting weld line between the films 5 and 6 is homogeneous, reliable, and of high quality. The films 5 and 6 are protected from deterioration—particularly from degradation by the rotary tool 9 of the outer layer 5a of the first film 5—by avoiding a kneading operation of the films 5 and 6, which would be in addition to the friction already present.

[0138] The Human-Machine Interface (HMI) is improved, the task of the human operator being simplified by being reduced to the entry of objective input data DE1 enabling reliable output data DS1 to be provided to the control module 12, after their selective and / or iterative processing by the computer 27 and by the regulation module 28 itself subdivided into two regulators 28a, 28b selectively processing the data provided by the calculation model 27a.

Claims

1. Method for friction welding via a rotary tool (9) between two superimposed heat-sealing films (5, 6), including a first film (5) and a second film (6), the films (5, 6) each including an outer layer (5a, 6a) and an inner layer (5b, 6b) which are heat-sealing, according to which method: - ) the films (5, 6) are installed superimposed on a platen (3) equipping a numerically controlled machine (1) (2) for friction welding the films (5, 6) to one another, the inner layers (5b, 6b) of the films (5, 6) being oriented towards one another in the position for welding the films (5, 6) to one another, the outer layer (6a) of the second film (6) being oriented towards the platen (3) and the outer layer (5a) of the first film (5) being oriented towards a welding head (4) carrying the rotary tool (9) and a motor (14) for driving the rotary tool (9) in rotation, - ) an operator enters input data (DE1) relating to at least the structural characteristics of the films (5.6) and a trajectory (TJ1) to be followed by the rotary tool (9) in axial contact with the outer layer (5a) of the first film (5), from which input data (DE1) and depending on instruction data transmitted by the numerical control (2) to a control module (12), the control module (12) generates control commands (OC1, AC2) at least relating on the one hand to driving the rotary tool (9) at a set rotational speed (VN1) and on the other hand to a displacement (DP1) of the welding head (4) according to the kinematics and dynamics of displacement (DP1) of the rotary tool (9) along said trajectory (TJ1) in order to obtain a set temperature (T3) for welding the films (5, 6) to one another, the method being characterised in that it has at least the following operations: - ) prior to the application of the rotary tool (9) against the first film (5) and under control of a calculation system (11) equipped with the numerical control (2), preheating the rotary tool (9) using an auxiliary heating means (16b, 17), to an initial set temperature (T1) capable of initiating melting of the inner layer (5b, 6b) of the films (5, 6), then - ) with the preheating of the rotary tool interrupted, carrying out friction welding of the films (5, 6) to one another via the rotary tool (9), by measuring and transmitting to said calculation system (11) the effective temperature (T2) continuously measured at the axial contact point against the first film (5) of the rotary tool (9) along the trajectory (TJ1) thereof, and by regulating via said calculation system (11) the rotational speed of the rotary tool (9) taking into account at least said measured effective temperature (T2), in order to obtain along said trajectory (TJ1) a heating temperature of the films (5.6) compliant with said welding set temperature (T3).

2. Method according to Claim 1, characterised in that the regulation of the rotational speed of the rotary tool (9) by the calculation system (11) also takes into account at least one of the following parameters: - ) the diameter (D1) of the rotary tool (9), - ) the rotational dynamics of the rotary tool (9), as a function of the speed of displacement (VD1) of the rotary tool (9) along said trajectory (TJ1) and the pressure (P1) exerted by the rotary tool (9) against the first film (5), - ) the intrinsic temperature of the films (5, 6) continuously measured at the axial contact point of the rotary tool (9) against the first film (5).

3. Method according to Claim 2, characterised in that the respective values of the speed of displacement (VD1) of the rotary tool (9) along said trajectory (TJ1) and the pressure (P1) exerted by the rotary tool (9) against the outer layer (5a) of the first film (5) are prioritised at constant values, the welding temperature of the films (5.6) being adapted by varying the rotational speed of the rotary tool (9) in order to obtain the welding set temperature (T3) maintained constant along the entire trajectory (TJ1) followed by the rotary tool (9).

4. Method according to either one of Claims 2 or 3, characterised in that the method includes, during the period of welding the films (5, 6) to one another and under control of the calculation system (11), an operation of heating a support (25) interposed between the second film (6) and the platen (3) on which the superimposed films (5, 6) rest, the heated support (25) raising the temperature of the superimposed films (5, 6) to a temperature threshold (S1) whose maximum value is as close as possible to the welding set temperature (T3) while remaining lower than the melting temperature of the outer layers (5a, 6a) of the films (5, 6).

5. Method according to any one of the preceding claims, characterised in that a calculation model (27a) implemented by a calculator (27) that includes the calculation system (11), determines output data (DS1) from said input data (DE1), the input data (DE1) further comprising at least the diameter (D1) of the rotary tool (9) and the output data (DS1) comprising at least the trajectory (TJ1) to be followed by the rotary tool (9), the speed of displacement (VD1) of the rotary tool (9), the pressure (P1) exerted by the rotary tool (9) against the first film (5), a nominal rotational speed (VN2) of the rotary tool (9) and the set temperature (T3) for welding the films (5, 6) to one another.

6. Method according to Claim 5, characterised: in that at least the output data (DS1) relating to the speed of displacement (VD1) of the rotary tool (9) and the pressure (P1) exerted by the rotary tool (9) against the first film (5) are prioritised by being directly transmitted and processed by said control module (12), and in that the calculation system (11) regulates via a regulation module (28) that it has the following values transmitted to the control module (12): - ) said initial set temperature (T1), from at least the output data (DS1) relative to the welding set temperature (T3), and - ) the effective rotational speed (VN1) of the rotary tool (9) to be applied by the control module (12), from the output data (DS1) relating to the nominal rotational speed (VN2) of the rotary tool (9), the output data (DS1) relating to the welding set temperature (T3) and the effective temperature (T2) of the rotary tool (9) measured continuously at the axial contact point between the first film (5) and the rotary tool (9) along its trajectory (TJ1).

7. Method according to any one of Claims 4 to 6, characterised in that said temperature threshold (S1) of the superimposed films (5, 6) heated via the support (25) is calculated by a calculation member (29) from the output data (DS1) relating to the welding set temperature (T3), said calculated temperature threshold (S1) lower than the welding set temperature (T3) being transmitted by the control module (12) controlling the activation of a heating member (26) of the support (25).

8. Method according to Claim 6, characterised: in that the input data (DE1) relate at least to the materials (M1) from which the films (5.6) are respectively derived, to the thickness (EP1) of the films (5,6), to the diameter (D1) of the rotary tool (9), and to the trajectory (TJ1) to be followed by the rotary tool (9), in that the output data (DS1) derived from the calculation carried out by the calculation model (27a) relate at least to the trajectory (TJ1) to be followed by the rotary tool (9), to the welding set temperature (T3), to a nominal rotational speed (VN2) of the rotary tool (9), to the pressure (P1) to be exerted against the outer layer (5a) of the first film (5) by the rotary tool (9) along its trajectory (TJ1) and to an optimised speed of displacement (VD1) of the rotary tool (9) along its trajectory (TJ1), and in that the regulation module (28) regulates at least: - ) the initial set temperature (T1) to be applied from the welding set temperature (T3) and the temperature difference of the outer layer (5a) of the first film (5) between the current axial contact point of the rotary tool (9) and a downstream axial contact point of the rotary tool (9) according to the direction of displacement (DP1) of the rotary tool (9) along its trajectory (TJ1), and - ) the effective rotational speed (VN1) of the rotary tool (9) to be applied from the welding set temperature (T3) and the nominal rotational speed (VN2) of the rotary tool (9), the regulation of the effective rotational speed (VN1) of the rotary tool (9) being corrected by said calculation system (11) equipping the numerical control (2) at least according to the effective temperature (T2) of the rotary tool (9) measured continuously at the axial contact point between the rotary tool (9) and the first film (5) along its trajectory (TJ1).

9. Method according to Claim 8, characterised in that, on the one hand, the output data (DS1) derived from the calculation carried out by the calculation model (27a) and, on the other hand, the regulation operations carried out by said regulation module (28), are iteratively calculated and correlated with each other to identify the limits of the welding domain conditioning the values of the operating parameters of the machine (1) to be applied by the control module (12) to perform the welding between the films (5, 6).

10. Numerically controlled (2) machine (1) for friction welding via a rotary tool (9) between two superimposed heat sealing films (5, 6), organised for carrying out a welding method according to any one of the preceding claims, the machine (1) being at least equipped: - ) with a said platen (3) for installing said superimposed films (5, 6), - ) with a said welding head (4) carrying the rotary tool (9) and a said motor (14) for driving the rotary tool (9) in rotation, - ) with a said manipulator (13) for displacement (DP1) of the welding head (4) along the three axes of an orthonormal reference frame, two axes of which define a plane for superimposing the films (5, 6) and the third axis of which defines the axial application direction of the rotary tool (9) against the superimposed films (5, 6), - ) with said numerical control (2) at least equipped with said input member (10) for an operator to input said input data (DE1), with a said calculation system (11) generating from the input data (DE1) the setpoints used by a said control module (12) which generates said control commands (OC1, AC2) relating to at least rotating the rotary tool (9) at said set rotational speed (VN1) and said displacement (DP1) of the welding head (4) according to the kinematics and dynamics of displacement (DP1) of the rotary tool (9) along a predefined trajectory (TJ1) in order to obtain at least one said set temperature (T3) for welding the films (5, 6) to one another, - ) with a said auxiliary heating means (16b, 17) of the rotary tool (9) to said initial set temperature (T1), the activation of which is regulated by the calculation system (11) equipping the numerical control (2), and - ) a temperature sensor (18) disposed inside an axial (A1) channel (19) that includes the rotary tool (9), the distal end (18b) of the temperature sensor (18) being placed inside the channel (19) near the end face (9c) of the rotary tool (9) via which the rotary tool (9) is axially applied against said outer layer (5a) of said first film (5), the machine (1) being characterised in that the calculation system (11) is configured to: - prior to the application of the rotary tool (9) against the first film (5), control the preheating of the rotary tool (9) using an auxiliary heating means (16b, 17), to an initial set temperature (T1) capable of initiating melting of the inner layer (5b, 6b) of the films (5, 6), then - the preheating of the rotary tool being interrupted, and, during the friction welding of the films (5, 6) to one another via the rotary tool (9), regulate the rotational speed of the rotary tool (9) taking into account at least one measured effective temperature (T2), in order to obtain along said trajectory (TJ1) a heating temperature of the films (5, 6) compliant with said welding set temperature (T3), the effective temperature (T2) corresponding to a temperature measured continuously at the axial contact point against the first film (5) of the rotary tool (9) along the trajectory (TJ1) thereof.

11. Machine (1) according to Claim 10, characterised in that the welding head (4) is equipped with an electronic board (20) for collecting information at least relating to the temperature detected by the temperature sensor (18) and the rotational dynamics of the rotary tool (9) detected by an accelerometer (21), the electronic board (20) being equipped with at least one wave communication device (23) via which the electronic board (20) transmits at least to the calculation system (11) the information collected by the electronic board (20).

12. Machine (1) according to either one of Claims 10 or 11, characterised in that said auxiliary heating means (16b, 17) is formed of a metal body (16b) that the rotary tool (9) has at its distal end (9b) for axial application (A1) against the first film (5) and a heating device (17) of the metal body (16b) which is mounted on the welding head (4).

13. Machine (1) according to any one of Claims 10 to 12, for carrying out a method according to Claim 4, characterised in that the machine (1) is equipped with a said support (25) interposed between said platen (3) and said second film (6), the support (25) being equipped with a heating member (26) whose activation by the control module (12) is dependent on the calculation system (11) equipping the numerical control (2).

14. Machine (1) according to any one of Claims 10 to 13, for carrying out a method according to any one of Claims 6 to 9, characterised in that the calculation system (11) includes a said calculator (27) for implementing said calculation model (27a), the calculator (27) being interfaced between the input member (10) and said regulation module (28) which the calculation system (11) has.

15. Machine (1) according to Claim 14, characterised in that the regulation module (28) is composed of at least two separate regulators (28a, 28b), including: - ) a first regulator (28a) determining the initial set temperature (T1) of the auxiliary heating means (16b, 17) of the rotary tool (9) from the welding set temperature (T3), and - ) a second regulator (28b) of the effective rotational speed (VN1) of the rotary tool (9) to be applied, from said nominal rotational speed (VN2), the welding set temperature (T3) and said effective temperature (T2) of the rotary tool (9) continuously measured by the temperature sensor (18) with which it is equipped.

16. Machine (1) according to any one of Claims 10 to 15, characterised in that the welding head (4) is equipped with a sensor (22) for measuring vibrations to which the rotary tool (9) is subjected, the activation of a generator (30) of an alert signal (30a) equipping the machine (1) being dependent on the vibration sensor (22) by being calibrated to a predefined threshold (S2) of the maximum tolerated frequency and / or amplitude of the vibrations measured by the vibration sensor (22).