Method and device for applying hot-melt adhesive

Abstract

The invention relates to a method for applying hot-melt adhesive to containers by means of a device (1) for applying hot-melt adhesive, wherein the device (1) comprises at least one application head (5, 5`) and a hot-melt adhesive line (3, 3a, 3a`) connected to the application head (5, 5`) for supplying the hot-melt adhesive to the application head (5, 5`), wherein the device (1) is started up from a first operating state to a second operating state at a higher power than the first operating state, wherein a hot-melt adhesive pressure (p) in the hot-melt adhesive line (3, 3a, 3a`) is increased, prior to or during the start-up of the device (1) to the second operating state, to a start-up pressure which is higher than an operating pressure associated with the power in the second operating state, wherein the start-up pressure is reduced to the working pressure in a time-dependent manner and / or according to a number of hot-melt adhesive applications that have been carried out, and wherein, in the second operating state, the device (1) is operated in such a way that the hot-melt adhesive pressure (p) in the hot-melt adhesive line (3, 3a, 3a`) corresponds to the working pressure

Description

[0001] Method and apparatus for applying hot melt adhesive

[0002] The invention relates to a method for applying hot melt adhesive to containers. Furthermore, the present invention also relates to a device for applying hot melt adhesive to containers.

[0003] Devices or systems for applying adhesives, in particular hot melt adhesives, are generally known. Such devices or systems typically have at least one application head, on which at least one nozzle, namely an adhesive nozzle, is provided, through which the adhesive or hot melt adhesive is dispensed.

[0004] Such devices or systems are also used in the beverage industry, for example, and particularly in packaging machines or systems for the production of container units. In this process, the containers to be processed into units are, for instance, coated with spot adhesive to bond them together. Such packaging machines or systems with a device for applying adhesive or hot melt adhesive are known, for example, from German patent applications DE 10 2012 100 810 A1 and EP 3 245 141 B1.

[0005] In the beverage industry, for example, various aspects are particularly important when producing containers from beverage containers, such as PET bottles, in order to manufacture containers of the required quality.

[0006] Firstly, when separating the container, delamination must be effectively prevented. This means ensuring that the adhesive causes PET layers to detach from the walls of the PET bottles, as such delamination can destabilize the PET bottles and ultimately lead to them bursting. Due to the beverage industry's efforts to reduce material and resource consumption, PET...

[0007] As the use of bottles with increasingly thinner walls becomes more common, the delamination aspect is gaining importance in the production of containers. Extensive test series conducted by the applicant have shown that delamination can be reduced or prevented if a foam adhesive is formed or produced from the hot melt adhesive and this foam adhesive is applied to the containers.

[0008] Another important aspect of producing high-quality containers is ensuring that the adhesive for spot bonding is applied to the containers in a consistently optimal quantity. For example, precisely measured amounts of adhesive, particularly within a range of 50 mg to 250 mg, must be applied to the containers in very short application times, while maintaining tight tolerances. These tight tolerances are crucial because any deviation in the amount of adhesive (either too high or too low) will result in defective containers. For instance, if too much adhesive is applied, the containers within a single container assembly will no longer be able to be separated.Otherwise, the containers of a given container set may fall apart on their own if the amount of adhesive applied is too small.

[0009] To ensure that the adhesive quantities remain precisely within the permissible tolerance range, certain precautions must be taken. A particularly important factor influencing adherence to the adhesive quantities is the pressure prevailing in the corresponding device for applying the hot melt adhesive, which can also be referred to as adhesive pressure, hot melt adhesive pressure, or system pressure.

[0010] In known devices or systems, this pressure is therefore set as precisely as possible, for example by means of a control system, in particular a pressure control system.

[0011] 12294 WO The inventors have recognized that pressure fluctuations can occur in devices or systems of the type mentioned above. Such pressure fluctuations can arise in particular depending on the operating state, for example at start-up, when starting up after an operational delay or after an operational stop, or when parameters are changed during a format change or the like, or also due to contamination, adhesive encrustation or wear during continuous operation, i.e. especially when the device is not operated at its rated power, but at a lower power than its rated power.

[0012] The object of the invention is to provide a method and a device for applying hot melt adhesive to containers that allows for higher process reliability and process accuracy.

[0013] The problem is solved by a method or device for applying hot melt adhesive to containers according to the features of the independent claims. Advantageous further developments and embodiments of the invention are specified in the respective dependent claims.

[0014] According to a first aspect, the present invention relates to a method for applying hot melt adhesive to containers using a hot melt adhesive application device. The device comprises at least one application head and a hot melt adhesive line connected to the application head for supplying the hot melt adhesive to the application head. In the method according to the invention, the device is ramped up from a first operating state to a second operating state with a higher power output than the first operating state, wherein the hot melt adhesive pressure prevailing in the hot melt adhesive line is increased before or during the ramp-up of the device to a starting pressure that is higher than the operating pressure associated with the power output in the second operating state.Furthermore, in the inventive method, the starting pressure is reduced to the working pressure depending on time and / or on the number of hot melt adhesive applications performed, and the device is operated in the second operating state in such a way that the.

[0015] 12294 WO the prevailing hot melt adhesive pressure in the hot melt line corresponds to the working pressure.

[0016] The "device" can also be understood, within the meaning of the present invention, as a system for applying hot melt adhesive and can be used, in particular, in a machine or plant for the production of containerized units, for example, so-called multipacks, or can also be a part or component of such a machine or plant. In particular, the device can be used in the beverage industry and be integrated into a treatment and / or packaging machine for treating and / or packaging beverage containers. The containers onto which the hot melt adhesive is applied by means of the present device are, for example, (beverage) cans or bottles, preferably PET bottles.

[0017] The device can include a hot melt adhesive tank for storing the hot melt adhesive. The hot melt adhesive line can essentially be designed as an adhesive line, for example, as a hose or pipe, particularly as a hot melt hose. Advantageously, the hot melt adhesive line can be connected to the hot melt adhesive tank or storage container, which can be heated, for example, by means of a preferably provided heating device. The hot melt adhesive, which is also synonymously referred to as glue, adhesive, or hot melt adhesive, can be heated by the heating device to a predetermined temperature, in particular to a melting temperature and / or processing temperature, so that the hot melt adhesive is maintained in a viscous, flowable form. The hot melt adhesive is also conveyed in this viscous, flowable state in the hot melt adhesive line.

[0018] The at least one application head provided in the device, which in this case can also be referred to as an application head or applicator head, or as an adhesive application head or glue application head, is designed, for example, in a manner known to those skilled in the art. In the present system, several application heads can also be provided, connected in parallel or in series, wherein

[0019] 12294 WO each of the multiple application heads is preferably equipped with at least one adhesive nozzle.

[0020] The applicator head, or each applicator head, dispenses the specified, precise amount of hot melt adhesive via the adhesive nozzle(s) and applies it to the containers, thereby creating pinpoint adhesive bonds. Each of these dispensing and application events can be referred to as an application process or a "shot." The applicator head, or each applicator head of the device, operates, for example, at a frequency of up to 500 application processes per minute.

[0021] In particular, the second operating state can be the regular working operation or rated power operation of the device, i.e. the operating state in which the device is operated at a predefinable rated power and the hot melt adhesive carried in the hot melt adhesive line is set at a hot melt adhesive pressure that corresponds to the rated power pressure for the rated power of the device in the second operating state.

[0022] Preferably, the operating pressure can be configured as the nominal operating pressure. In contrast, the first operating state can preferably be a machine standstill of the device with a lower device output compared to the second operating state. Device output can be understood as the number of containers treated per unit of time, for example, per hour. Alternatively, device output can also be related to the number of application processes generated by the application head per unit of time.

[0023] According to the invention, it was recognized that during the first operating state of the device, for example, when the machine is at a standstill, a pressure drop in the hot melt adhesive line can occur. Since the device, often consisting of several meters of hot melt adhesive line, is a relatively inert fluidic system, the initial pressure drop during startup or restart of the device into the second operating state is sufficient, i.e., for a defined period and / or for a defined number of the first hot melt adhesive applications.

[0024] 12294 WO Applications: The usual operating pressure of the hot melt adhesive in the hot melt line is insufficient to deliver a constant, desired amount of hot melt adhesive to the application head for each application process, even during startup or restart of the device. Instead, significant—and therefore undesirable—tolerances occur in the amount of adhesive dispensed per application, resulting in rejects of incorrectly or poorly sealed containers or packages.

[0025] The method according to the invention therefore proposes to first increase the hot melt adhesive pressure prevailing in the hot melt line before or during the start-up of the device to a starting pressure that is higher than a working pressure associated with the power in the second operating state, and then, after reaching the starting pressure, to reduce the starting pressure back to the working pressure – in a time-dependent manner and / or depending on the number of hot melt adhesive applications carried out – before, upon reaching the power of the second operating state, the hot melt adhesive pressure in the hot melt line corresponds again to the working pressure.

[0026] This initial pressure increase of the hot melt adhesive in the hot melt line to a higher start-up pressure compared to the operating pressure ensures that a consistently desired amount of hot melt adhesive is dispensed at the application head for each application process, even during the initial startup of the device. The inventor recognized that, before starting the application process after a machine shutdown, the hot melt adhesive pressure in the hot melt line must first be set to a higher start-up pressure than the normal operating pressure. This ensures a precise and exact amount of adhesive, within a narrow tolerance range, is dispensed at the application head for each application process during the initial startup phase of the device.This pressure increase of the hot melt adhesive pressure in the hot melt adhesive line is then preferably reduced back to the working pressure during the start-up process of the device until the performance of the rated power operation, i.e. the second operating state, is reached.

[0027] 12294 WO. Advantageously, this method according to the invention leads to significantly fewer tolerances or fluctuations in the dispensing of the adhesive quantities during the start-up process of the device from the first operating state to the second operating state. In particular, it can be provided that the application of hot melt adhesive to the containers only begins when the hot melt adhesive pressure in the hot melt adhesive line has reached the start-up pressure – i.e., when it has been increased to the start-up pressure.

[0028] The method according to the invention offers further advantages in that it also takes into account pressure fluctuations that occur and compensates for them by increasing the pressure during the startup of the device. In particular, pressure fluctuations that occur depending on the operating state of the system can be compensated for, thereby ensuring that a desired, constant hot melt adhesive pressure can be maintained independently or essentially independently of the operating state.

[0029] The process reliability and accuracy of the device are thus significantly increased compared to conventional devices. This also means, in particular, that when manufacturing container assemblies by gluing, the same required, defined amount of adhesive is applied to the containers in every application process, ensuring stable, high-quality container assemblies. The required amount of adhesive can be precisely and accurately maintained within a narrow tolerance range. This also allows for a reduction in the tolerances of the adhesive spot weights.

[0030] According to an advantageous embodiment, the starting pressure is reduced to the working pressure following a characteristic curve, in particular by a linear reduction. The characteristic curve can be formed by a mathematical function. In particular, the characteristic curve can be a linear function, especially a straight line. A linear reduction of the starting pressure enables a smooth and controlled adjustment of the hot melt adhesive pressure to the working pressure. This avoids abrupt pressure drops, which would otherwise lead to fluctuations.

[0031] 12294 WO could lead to variations in the adhesive quantity. This stabilizes the application process and ensures a constant adhesive dosage from the start of the startup phase until the operating pressure is reached. Since the characteristic curve is preferably mathematically defined, the pressure drop can be precisely predicted and controlled. This increases process accuracy, as controlling the hot melt adhesive pressure along a linear function is easily programmable and reproducible. This allows for identical results even under varying production conditions. By controlling the reduction of the startup pressure, the adhesive quantity per application is regulated more precisely, thus minimizing tolerances. The linearly controlled pressure drop ensures that the desired amount of adhesive is dispensed precisely at the application head throughout the entire startup phase, which is particularly important to avoid material losses and rejects due to incorrectly glued containers.The controlled reduction of the start-up pressure allows for more precise regulation of the adhesive quantity per application, thereby minimizing tolerances. The linearly controlled pressure reduction ensures that the desired amount of adhesive is dispensed exactly at the applicator head throughout the entire start-up phase, which is particularly important to prevent material loss and rejects due to incorrectly glued containers.

[0032] According to an advantageous embodiment, the first operating state can be a machine standstill, and the device is started up from this standstill to the second operating state. Alternatively, the first operating state could be a standby mode, an idle operation with a maintenance run, a slow operation, or a partial load operation. In standby mode, the device can remain switched on, but it does not perform any application processes or operates at significantly reduced power. The hot melt adhesive pressure in the line can be lowered to save energy and protect the components. The starting pressure ensures an immediate and consistent amount of adhesive per application when starting up from standby mode, as the pressure increase creates an initial pressure build-up that overcomes the inertia effect in the line.This enables a rapid resumption of production without material waste due to insufficient adhesive dosage.

[0033] 12294 WO In idle operation with maintenance mode, the device runs at minimum power to keep certain parts moving, thus preventing, for example, contamination or blockages in the hot melt adhesive line, without actually performing any application processes. During the transition from maintenance operation to full power operation, the start-up pressure ensures a stable adhesive metering from the first application. This ensures that no fluctuations or material losses occur and that the device can be operated immediately at full efficiency.

[0034] In slow or partial load operation, the device operates at low power, for example, to process small production quantities or to wait for upstream or downstream production processes. Starting up from slow operation to full power ensures a constant amount of adhesive, as the increased starting pressure prevents pressure build-up delays in the line from causing adhesive deficiencies. This improves dispensing accuracy and reduces the risk of defective bonds during load changes. This design variant significantly increases the flexibility and efficiency of the device by allowing a quick and lossless switch from the initial operating state (e.g., standby, idle, or slow operation) to full power operation.The targeted pressure increase during startup ensures precise and constant adhesive dosing, resulting in material savings and higher production quality. This method is particularly helpful in reducing production rejects during load changes or operational interruptions, and enables consistently high process reliability.

[0035] According to an advantageous embodiment, the device for applying foam adhesive to containers may be designed and comprise at least one foaming device, wherein a foam adhesive is produced from the hot melt adhesive and applied to the containers as foam adhesive. Preferably, a foam adhesive with a defined foaming rate is applied to the container. It is also conceivable to consider embodiments in which the hot melt adhesive tank and the foaming device are arranged spatially adjacent to each other in such a way as to form an essentially integrated or combined structural unit.

[0036] 12294 WO For example, the foaming device connects directly to the hot melt adhesive tank, so that the hot melt adhesive line is limited to a minimal transition between an outlet of the hot melt adhesive tank and an inlet of the foaming device. Preferably, the foaming device is designed to produce a foam adhesive with a defined foaming rate, which in this case can also be referred to as the foaming rate or the foaming rate.

[0037] The foaming rate essentially indicates the volume ratio in which gas is introduced into the hot melt adhesive when it is applied. The foaming rate thus provides information about the volume increase of the hot melt adhesive during foaming, i.e., the relative increase in volume experienced by the hot melt adhesive during foaming, particularly due to gas inclusions or the gas introduced into the hot melt adhesive by applying the gas. This increase is determined by the relative amount of gas in the hot melt adhesive-gas mixture and by the corresponding expansion of the introduced gas upon pressure release at the nozzle outlet of the applicator head.

[0038] The foaming action increases the volume of the hot melt adhesive while reducing the actual amount of material used. Because the hot melt adhesive is mixed with gas, less adhesive is needed to cover the same area. This reduction in adhesive consumption lowers production costs and conserves resources. Significant material savings can be achieved, especially in high-volume applications such as the production of multipacks in the beverage industry. A key advantage of using foam adhesive with thin-walled PET bottles is the protection of the delicate material structure, particularly preventing delamination of the laminate layers. PET bottles, especially thin-walled versions, are often composed of multiple layers of material that provide specific properties such as durability and protection.In particular, when opening the packs, i.e. separating the containers, conventional hot melt adhesives can cause problems.

[0039] 12294 WO sensitive laminate layers may be damaged, which can lead to delamination.

[0040] According to an advantageous embodiment, the increase of the working pressure to the start-up pressure and / or the reduction of the start-up pressure to the working pressure can be controlled by at least one control device via a pressure control loop. The control device automatically and precisely regulates the transition from the working pressure to the start-up pressure and back again via the pressure control loop. The pressure control within the loop ensures a consistent pressure adjustment according to definable specifications, without requiring manual intervention. This precise control reduces fluctuations in the hot melt adhesive pressure and ensures that the amount of adhesive dispensed in each application process remains precisely within the desired tolerance range. This results in higher dispensing accuracy and reduces material waste and defective bonds, which is particularly advantageous in high-volume and rapid production processes.

[0041] The pressure control loop can be configured for different operating states of the device and adjust the start-up pressure accordingly. This is particularly useful when the device transitions from its first to its second operating state, such as when starting up from a machine standstill or standby mode. Automatic adjustment of the pressure control loop to different operating states can also be implemented. Automatic adjustment to various operating states increases the device's flexibility and enables rapid, reliable pressure adjustment at production start-up without the need for manual readjustment of process parameters. This enhances process reliability and simplifies the management of load changes during production.The use of a pressure control loop in conjunction with a control and / or regulating device for adjusting the hot melt adhesive pressure enables highly precise, automated control of the application process. This design variant contributes to improved process reliability, flexibility, efficiency, and the longevity of the equipment, and ensures consistent adhesive quality, even under changing operating conditions.

[0042] 12294 WO According to an advantageous embodiment, the increase of the working pressure to the start-up pressure and / or the reduction of the start-up pressure to the working pressure can be controlled as a function of an application pressure of the hot melt adhesive, which is detected by means of an application pressure sensor assigned to the at least one application head. The application pressure at the application head is detected by the at least one application pressure sensor belonging to the pressure control circuit, in particular directly at the application head, for example, directly at the adhesive nozzle of the application head.

[0043] The application pressure sensor is advantageous because it is designed to detect the application pressure of the foam adhesive directly at the application head. This allows the application pressure, which serves as the actual value, to be measured as close as possible to the application point, further increasing accuracy. Based on this detected application pressure, the hot melt adhesive pressure is then controlled all the way to the application head and maintained at a predefined target value. Direct pressure measurement at the application head allows for more precise application pressure detection and immediate identification of fluctuations. This enables the pressure control loop to maintain the hot melt adhesive pressure in real time and as close as possible to the actual application point. This precise pressure control minimizes tolerances and ensures that the amount of adhesive is dispensed exactly in every application process.This is particularly important to ensure a uniform and clean bond, resulting in a more stable connection between the containers and reduced rejects. Direct pressure monitoring via an application pressure sensor on the application head and the resulting control of the hot melt adhesive pressure guarantee highly precise and consistent adhesive dispensing. This significantly increases the quality of the bonds, process reliability, and the flexibility of the equipment.

[0044] Advantageously, the hot melt adhesive can be provided for by means of a controllable and / or adjustable pump unit of the device to the at least one application head, the pump unit being controlled via the pressure control circuit. The control and / or adjustment device of the pressure control circuit is required for this purpose.

[0045] 12294 WO is set up to act on the pump unit depending on the application pressure measured by the application pressure sensor. The pump unit is designed to deliver the hot melt adhesive to at least one application head under a predefinable hot melt adhesive pressure.

[0046] In addition to pumping the hot melt adhesive, the pump unit is preferably also designed to build up hot melt adhesive pressure in the hot melt adhesive line, specifically to generate pressure with which the hot melt adhesive is supplied to the at least one application head. This pressure is also referred to as hot melt adhesive pressure. Thus, according to the present invention, the pump unit is designed to build up pressure upstream of the application head, particularly in the supply line to the application head. The device may also have several pump units. Particularly in embodiments of the device that include a foaming device, it may be advantageous if the pump unit is associated with the foaming device, or if the foaming device includes the pump unit, and a further pump unit is associated with the hot melt adhesive tank.The pump unit of the foam formation device and the additional pump unit of the hot melt adhesive tank can be independently controllable. The pump unit and the additional pump unit can then be connected in series in the hot melt adhesive line and interact fluidically.

[0047] It is further advantageous that the pump unit is designed as a multi-stage gear pump. The multi-stage gear pump allows the hot melt adhesive to be transformed into a foam adhesive. The pressure control loop acts specifically on the multiple stages of the multi-stage gear pump. In this way, the pressure control loop can particularly benefit the motor-driven drive gears of the individual stages of the gear pump by regulating the rotational speed of the drive gears. This can also be understood as drive control of the multiple stages of the multi-stage gear pump.

[0048] 12294 WO According to an advantageous embodiment, the hot melt adhesive pressure prevailing in the hot melt line can be increased to the start-up pressure before or during the start-up of the device to the second operating state, depending on application- and / or product- and / or device-specific parameters. This adaptive pressure control improves the adhesive quality and reduces material waste, as the adhesive application can be precisely tailored to the specific conditions. For example, such product-specific parameters can be the material thickness of the containers (e.g., thin-walled PET bottles, cans) and their volume (e.g., 0.5-liter or 2-liter bottles). Different container types and sizes have varying material thicknesses and resistances. A precisely adjusted start-up pressure prevents thin-walled containers from being deformed or damaged by excessive pressure.Especially with thin containers, such as PET bottles, optimally adjusted pressure reduces the risk of delamination. At the same time, it ensures the stability of the bond with more robust materials, thereby reducing rejects and material waste. Application-specific parameters can include, for example, the viscosity of the adhesive at a specific operating temperature and its curing behavior (e.g., fast or slow curing). Higher viscosity adhesives may require higher pressure for uniform application, while low-viscosity adhesives operate at a lower initial pressure. Adjusting the pressure to the adhesive properties ensures a consistent adhesive output and prevents over- or under-application, resulting in greater precision and tighter tolerances in the amount of adhesive applied. This improves bond quality and minimizes material waste due to excess adhesive.Device-specific parameters can include, for example, the production speed (number of application cycles per minute) or the length of the device's downtime. At higher production speeds, the start-up pressure must be regulated so that it is quickly reduced to the required operating pressure to avoid delays in the production process. Flexible pressure adjustment allows for rapid ramp-up and shutdown and ensures a stable and continuous adhesive supply. This guarantees consistent quality even at high cycle rates and increases the efficiency and reliability of the system. The start-up pressure depends on specific application-related factors.

[0049] The 12294 WO product- and device-specific parameters enable flexible and highly precise control of the hot melt adhesive pressure, ensuring both material savings and improved adhesive quality. By optimizing parameters for container material, adhesive properties, environmental influences, production speed, and application pattern, a robust and adaptable application solution is created that meets the demands of variable production conditions.

[0050] According to an advantageous embodiment, the initial starting pressure can be set to a pressure that is 5 to 15 bar, particularly 10 bar, or 10% to 30%, particularly 20%, higher than the operating pressure. A starting pressure selected within these specified ranges enables a faster pressure build-up in the device. In the context of this invention, the term 'initial starting pressure' is understood to mean the initially set pressure to which the hot melt adhesive pressure in the hot melt line is increased before or during the device's ramp-up to the second operating state (e.g., rated power operation). This initial value serves as the starting point for the start-up pressure, which is deliberately higher than the regular operating pressure to ensure the initial pressure increase necessary to compensate for the inertia loss during the device's ramp-up.This is particularly advantageous when the device is started up from a standstill, as it ensures an immediate response to pressure requirements during production start-up. This avoids delays and inefficient production times that could result from a slow pressure build-up. Such a preset start-up pressure ensures a constant and precise adhesive dispensing even in the early stages of application. This minimizes tolerances in the amount of adhesive applied and reduces the likelihood of under- or over-dosing, which could lead to a faulty bonding process. This is crucial, especially during the initial machine start-up, to guarantee high bonding quality.Surprisingly, it has been shown that deliberately setting the starting pressure 5 to 15 bar or 10% to 30% higher than the working pressure improves the efficiency and quality of the bonding process.

[0051] 12294 WO maximizes this. This pressure adjustment enables faster and more stable application, reduces adhesive dispensing tolerances, prevents clogging, and ensures improved adaptation to variable production conditions. All these factors contribute to higher productivity and a better end product.

[0052] According to an advantageous embodiment, the number of adhesive applications required to reduce the start-up pressure to the operating pressure can be selected in the range of 100 to 200, preferably 130 to 170, and particularly preferably approximately 150. By specifying a number of approximately 150 applications, it has surprisingly been found that the pressure within the device remains particularly stable. Reducing the start-up pressure too early leads to fluctuations and inconsistencies in the adhesive dispensing, while reducing it too late impairs efficiency. This specified number of adhesive applications allows the pressure reduction to be carried out after an appropriate number of applications, which increases the stability of the process.Targeted adjustment of the number of adhesive applications to a range of 100 to 200 (especially around 150) enables precise control of the bonding process, minimizes tolerances, stabilizes pressure, and improves production efficiency. This approach helps ensure consistently high product quality and optimizes the entire production process.

[0053] According to an advantageous embodiment, the containers can be joined together after the hot melt adhesive has been applied to form a single unit, preferably with a carrying handle attached to the resulting container. Joining the containers, preferably simultaneously, after the hot melt adhesive has been applied results in increased stability of the entire unit. The correct positioning of the containers and the even distribution of the adhesive contribute to the unit remaining stable during transport and storage. This is particularly important in the beverage industry, where safe handling is essential. The application of a carrying handle to the unit allows for easier and more convenient handling by the end user. The carrying handle facilitates carrying and transporting the unit.

[0054] 12294 WO Containers, resulting in a better user experience. This can also influence purchasing decisions, as consumers often prefer products with user-friendly packaging. Integrating container joining, hot melt adhesive application, and handle attachment into a single production process increases efficiency. This optimizes the entire production flow by reducing changeover and setup times, leading to higher productivity and lower operating costs. Performing multiple steps (applying the adhesive, joining the containers, and attaching the handle) allows for increased production speed. This enables the production of a larger number of containers in less time, which is particularly beneficial in high-speed production lines.The design variant in which the containers are joined after the hot melt adhesive is applied and a carrying handle is attached offers significant technical advantages in terms of stability, handling, efficiency, production speed, and flexibility. These aspects not only contribute to improving the bonding process but also increase the overall quality of the final product.

[0055] According to a further aspect, the present invention also relates to a device for applying hot melt adhesive to containers. The device comprises at least one hot melt adhesive tank for storing a hot melt adhesive, at least one applicator head for applying the hot melt adhesive to the containers, and a hot melt adhesive line fluidically connecting the at least one applicator head to the hot melt adhesive tank for supplying the hot melt adhesive to the at least one applicator head.Furthermore, the device comprises at least one control and / or regulating device which is designed and configured to control and / or regulate the device in such a way that, before or during a start-up of the device from a first operating state to a second operating state with a higher power than the first operating state, a hot melt adhesive pressure prevailing in the hot melt line is increased to a start-up pressure which is higher than a working pressure associated with the power in the second operating state, and the start-up pressure is time-dependent and / or dependent on a number of successful events.

[0056] 12294 WO ter hot melt adhesive applications is reduced to the working pressure, wherein the device in the second operating state can be operated in such a way that the hot melt adhesive pressure prevailing in the hot melt adhesive line corresponds to the working pressure.

[0057] According to a particularly preferred embodiment of the device, it can be provided that the device has a pressure control circuit with at least one application pressure sensor connected to the control and / or regulating device for detecting an application pressure of the hot melt adhesive prevailing at the application head.

[0058] According to a preferred embodiment of the device, a foaming device for applying a gas, in particular nitrogen, to the hot melt adhesive to produce a foam adhesive can be arranged between the hot melt adhesive tank and the at least one application head, wherein the foaming device comprises at least one controllable and / or adjustable pump unit, preferably a multi-stage, controllable and / or adjustable pump unit, and a gas supply for applying the gas to the hot melt adhesive, wherein the pump unit is designed to convey the gas-treated hot melt adhesive to the at least one application head under the hot melt adhesive pressure.

[0059] According to a preferred embodiment of the device, the control and / or regulating device may be configured to act on the pump unit depending on the application pressure detected by the application pressure sensor.

[0060] The invention will be explained in more detail below with reference to exemplary embodiments shown in the figures. The figures show:

[0061] Fig. 1, in an exemplary and highly simplified manner, sketches an embodiment of a device for carrying out the method according to the invention using a roughly schematic block diagram and

[0062] 12294 WO Fig. 2 also illustrates, by way of a rough schematic block diagram, another embodiment of the device for applying hot melt adhesive in an exemplary and highly simplified manner.

[0063] For identical or similarly functioning elements of the invention, identical reference numerals are used in the figures, where appropriate. Furthermore, for the sake of clarity, only reference numerals necessary for describing the respective figure are shown in the individual figures. The invention is also presented in the figures only as a schematic view to illustrate its operation. In particular, the representations in the figures serve only to explain the fundamental principle of the invention.

[0064] Figures 1 and 2 each show exemplary embodiments of a device 1 for applying hot melt adhesive in a highly simplified and roughly schematic, diagrammatic representation. The embodiments of the respective devices 1 shown in Figures 1 and 2 are designed to carry out the inventive method for applying hot melt adhesive to containers.

[0065] The exemplary device 1 is preferably used in a container handling machine or system, in particular in a packaging machine for the production of container units, for example in the beverage industry. The device 1 can also be a component of such a packaging machine and, as such, can be structurally integrated into the packaging machine.

[0066] The device 1 generally includes an adhesive supply for providing a hot melt adhesive, specifically an adhesive supply with a hot melt adhesive tank 2 for storing the hot melt adhesive. In the illustrated examples, the hot melt adhesive tank 2 is associated with a pre-melter in which the hot melt adhesive can be heated, for example, to a suitable temperature corresponding to a melting or processing temperature, so that the hot melt adhesive is in a viscous, flowable form.

[0067] 12294 WO and is available for use in this configuration. For this purpose, for example, a heating device (not shown and not further described in the figures) is provided, by which, in particular, the hot melt adhesive tank 2 can be heated.

[0068] Furthermore, the device 1 has at least one applicator head 5, 5' for applying the hot melt adhesive to the containers and a hot melt adhesive line 3 fluidically connecting the at least one applicator head 5, 5' with the hot melt adhesive tank 2 for supplying the hot melt adhesive to the at least one applicator head 5, 5'.

[0069] Furthermore, the device 1 has at least one control and / or regulating device 100, which is designed and configured to control and / or regulate the device 1 in such a way that, before or during a start-up of the device 1 from a first operating state to a second operating state with a higher power than the first operating state, the hot melt adhesive pressure prevailing in the hot melt line 3 is increased to a start-up pressure that is higher than a working pressure associated with the power in the second operating state, and the start-up pressure is reduced to the working pressure depending on time and / or depending on the number of hot melt adhesive applications carried out, wherein the device 1 can be operated in the second operating state in such a way that the hot melt adhesive pressure prevailing in the hot melt line 3 corresponds to the working pressure.

[0070] In other words, in the method according to the invention, the device 1 is ramped up from a first operating state to a second operating state with a higher power output than in the first operating state. The hot melt adhesive pressure prevailing in the hot melt line 3 is increased before or during the ramp-up of the device 1 to a starting pressure that is higher than the working pressure corresponding to the power output in the second operating state. Subsequently, the starting pressure is reduced to the working pressure depending on time and / or the number of hot melt adhesive applications performed, and the device 1 is operated in the second operating state such that the hot melt adhesive pressure prevailing in the hot melt line corresponds to the working pressure. The starting pressure can be adjusted according to a characteristic curve.

[0071] 12294 WO operating pressure can be reduced. In particular, the starting pressure can be reduced linearly. The first operating state can, for example, be a machine standstill, and the device 1 can be started up from the machine standstill and ramped up to the second operating state. The hot melt adhesive pressure p prevailing in the hot melt line 3 before or during the ramp-up of the device 1 to the second operating state can be increased to the starting pressure depending on application- and / or product- and / or device-specific parameters.

[0072] In particular, it can be provided that the initial pressure for the start-up is set to a pressure that is 5 to 15 bar, particularly 10 bar, or 10% to 30%, particularly 20%, higher than the working pressure. Alternatively or cumulatively, it can also be provided that the number of adhesive applications required to reduce the start-up pressure to the working pressure is selected in the range of 100 to 200, preferably 130 to 170, and most preferably approximately 150 adhesive applications.

[0073] In more detail, the two exemplary embodiments of the device 1 shown in Figures 1 and 2 each have an optional foaming device 7 and are thus designed for applying foam adhesive to containers, since a foam adhesive is produced from the hot melt adhesive by means of the respective foaming device 7 and applied to the containers as foam adhesive.

[0074] Starting from and connected to the hot melt adhesive tank 2, the hot melt adhesive line 3 leads to the foaming device 7 belonging to the device 1, which is also connected to the hot melt adhesive line 3. The hot melt adhesive tank 2 is thus fluidically sealed to the foaming device 7 via the hot melt adhesive line 3, so that the hot melt adhesive, which is present in viscous, flowable form in the hot melt adhesive tank 2, can be supplied to the foaming device 7 via the hot melt adhesive line 3. The hot melt adhesive is supplied to the foaming device 7 at the inlet side via a hot melt adhesive inlet 11 of the foaming device 7.

[0075] 12294 WO The foaming device 7, which can also be referred to synonymously as a foaming unit, is designed to pressurize the hot melt adhesive supplied by a pump unit 14 belonging to the device 1 with a gas, in particular nitrogen, and in this way to produce a hot melt adhesive-gas mixture from the supplied hot melt adhesive in order to generate a foam adhesive. The structural and functional design of the foaming device 7 is described in more detail below in connection with the example of Figure 2.

[0076] To supply the hot melt adhesive-gas mixture or the foam adhesive produced in the foaming device 7 to at least one application head 5, 5' intended for applying the foam adhesive to the containers, the hot melt adhesive line 3 has a supply line 3a which is connected to the foaming device 7 at its outlet, namely to one or via an outlet 12, 12' of the foaming device 7 in a fluidically tight manner. The hot melt adhesive-gas mixture produced in the foaming device 7 is conveyed out of the foaming device 7 via the supply line 3a of the hot melt adhesive line 3 and transported towards the application head(s) 5, 5'.

[0077] In the example of Figure 1, the device 1 has one applicator head 5, and in the example of Figure 2, two applicator heads 5, 5'. The applicator head 5 or the applicator heads 5, 5' are fluidically connected to the foaming device 7 via the supply line 3a, 3a' of the hot melt adhesive line 3, with each applicator head 5 being equipped with a respective adhesive nozzle 5.1, through which the foam adhesive is dispensed or applied to the containers during operation of the device 1.

[0078] Application processes are thus carried out at each application head 5, 5', in particular at a predetermined frequency, whereby in each application process a specific, precisely metered quantity of foam adhesive is dispensed and applied to the respective containers. Optionally, the feed line 3a, 3a' of the

[0079] 12294 WO The hot melt adhesive line 3 and / or the applicator head(s) 5, 5' must be designed to be heatable in order to prevent cooling and premature, undesirable solidification of the hot melt adhesive gas mixture during conveying.

[0080] In the present device 1, the hot melt adhesive is actively conveyed, in particular pumped, from the hot melt adhesive tank 2 to the foaming device 7, wherein the device 1, according to the embodiments shown here, comprises the controllable and / or adjustable pump unit 14 and a further pump unit 6 arranged in series therewith in the hot melt adhesive line 3. During operation, the controllable and / or adjustable pump unit 14 in particular builds up a pressure in the hot melt adhesive line 3 or the supply line 3a, 3a' of the hot melt adhesive line 3, which is understood here as the hot melt adhesive pressure p of the hot melt adhesive in the hot melt adhesive line 3.

[0081] The hot melt adhesive, which is fed into the foaming device 7 via the hot melt adhesive inlet 11, is pressurized with gas, in particular nitrogen, by means of a gas supply 13, which in the example of Figure 2 is connected to a gas reservoir 13a (which may optionally be part of the device 1 or external). The gas or nitrogen is supplied at a constant gas or nitrogen pressure of, for example, 4 bar. To produce a uniform hot melt adhesive-gas mixture and to convey the gas-pressurized hot melt adhesive at a hot melt adhesive pressure p in the hot melt adhesive line 3 to the at least one application head 5, 5', the controllable and / or adjustable pump units 14 are preferably provided in the foaming device 7.

[0082] In other words, the hot melt adhesive is conveyed to the at least one application head 5, 5' by means of the controllable and / or adjustable pump unit 14 of the device 1, the pump unit 14 being controlled via a pressure control circuit RC. The pump unit 14 is designed as a multi-stage gear pump with several stages 14.n. The increase of the working pressure to the start-up pressure and / or the reduction of the start-up pressure to the working pressure can be controlled by means of the control and / or adjustment device 100 via the pressure control circuit RC.

[0083] 12294 WO Since the device 1 in the example of Figure 2 comprises two application heads 5, 5', the foaming device 7 also has two controllable and / or adjustable pump units 14, 14', each of which is assigned to a respective application head 5, 5' and is designed to pump the hot melt adhesive supplied with the gas under a hot melt adhesive pressure p, p' in the hot melt adhesive line 3 to the respective application head 5, 5'.

[0084] The pressure control circuit RC comprises the control and / or regulating device 100 and respective application pressure sensors 10, 10', each directly attached to each application head 5, 5', which detect and measure the application pressure of the hot melt adhesive directly at the respective application head 5, 5'. The increase of the working pressure to the start-up pressure and / or the reduction of the start-up pressure to the working pressure can be controlled depending on the application pressure of the hot melt adhesive, which is detected by the application pressure sensor 10 assigned to at least one application head 5.

[0085] The invention has been described above using exemplary embodiments. It is understood that numerous modifications or adaptations are possible without departing from the underlying inventive concept.

[0086] 12294 WO Reference List

[0087] 1 Device for applying hot melt adhesive

[0088] 2 hot melt adhesive tanks

[0089] 3 Hot melt adhesive line

[0090] 3a, 3a' Supply lines

[0091] 5.5' Applicator head

[0092] 5.1 Adhesive nozzle

[0093] 6 additional pump units

[0094] 7 Foam forming device

[0095] 10, 10' Application pressure sensors

[0096] 11 Hot melt adhesive inlet

[0097] 12, 12' Exit

[0098] 13 Gas supply

[0099] 13a Gas storage tank

[0100] 14, 14' Pump unit

[0101] 14. n stage of the pump unit

[0102] 100 Control and / or regulating device

[0103] P, P' Hot melt adhesive printing

[0104] RC pressure control circuit

[0105] 12294 WO

Claims

Patent claims 1. A method for applying hot melt adhesive to containers using a hot melt adhesive application device (1), wherein the device (1) comprises at least one application head (5, 5') and a hot melt adhesive line (3, 3a, 3a') connected to the application head (5, 5') for supplying the hot melt adhesive to the application head (5, 5'), wherein the device (1) is started up from a first operating state to a second operating state with a higher power output than the first operating state, wherein a hot melt adhesive pressure (p) prevailing in the hot melt adhesive line (3, 3a, 3a') is increased before or during the start-up of the device (1) to the second operating state to a starting pressure that is higher than a working pressure associated with the power output in the second operating state, wherein the starting pressure is reduced to the working pressure depending on time and / or on the number of hot melt adhesive applications performed.and wherein the device (1) is operated in the second operating state such that the hot melt adhesive pressure (p) prevailing in the hot melt adhesive line (3, 3a, 3a') corresponds to the working pressure.

2. Method according to claim 1, characterized in that the starting pressure is reduced to the working pressure following a characteristic curve, in particular by being reduced linearly.

3. Method according to claim 1 or 2, characterized in that the first operating state is a machine standstill and the device (1 ) is started from the machine standstill and brought up to the second operating state.

4. Method according to one of the preceding claims, characterized in that the device (1 ) is designed for applying foam adhesive to containers and comprises at least one foam formation device (7), wherein a foam adhesive is produced from the hot melt adhesive and is applied to the containers as foam adhesive. 12294 WO 5. Method according to one of the preceding claims, characterized in that the increase of the working pressure to the starting pressure and / or the reduction of the starting pressure to the working pressure is controlled by means of at least one control and / or regulating device (100) via a pressure control loop (RC).

6. Method according to claim 5, characterized in that the increase of the working pressure to the start-up pressure and / or the reduction of the start-up pressure to the working pressure is controlled as a function of an application pressure of the hot melt adhesive, which is detected by means of an application pressure sensor (10, 10') associated with the at least one application head (5, 5').

7. Method according to claim 5 or 6, characterized in that the hot melt adhesive is conveyed to the at least one application head (5, 5') by means of a controllable and / or adjustable pump unit (14, 14') of the device, wherein the pump unit (14, 14') is controlled via the pressure control circuit (RC).

8. Method according to claim 7, characterized in that the pump unit (14, 14') is designed as a multi-stage gear pump.

9. Method according to one of the preceding claims, characterized in that the hot melt adhesive pressure (p) prevailing in the hot melt adhesive line (3, 3a, 3a') is increased to the start-up pressure before or during the start-up of the device (1) to the second operating state depending on application- and / or product- and / or device-specific parameters.

10. Method according to one of the preceding claims, characterized in that the starting pressure is set to a pressure which is 5 to 15 bar, in particular 10 bar, or 10% to 30%, in particular 20%, higher than the working pressure. 12294 WO 11. Method according to one of the preceding claims, characterized in that the number of adhesive applications performed for reducing the start-up pressure to the working pressure is selected in a range of 100 to 200, preferably 130 to 170, particularly preferably approximately 150 adhesive applications.

12. Method according to one of the preceding claims, characterized in that the containers are brought together after the application of the hot melt adhesive to form a container, wherein a carrying handle is preferably applied to the container formed from the containers.

13. Device (1) for applying hot melt adhesive to containers, comprising at least one hot melt adhesive tank (2) for storing a hot melt adhesive, at least one application head (5, 5') for applying the hot melt adhesive to the containers, and a hot melt adhesive line (3, 3a, 3a') fluidically connecting the at least one application head (5, 5') to the hot melt adhesive tank (2) for supplying the hot melt adhesive to the at least one application head (5, 5'), wherein the device (1) comprises at least one control and / or regulating device (100) which is designed and configured to control and / or regulate the device (1) such that, before or during a start-up of the device (1) from a first operating state to a second operating state with a higher power than the first operating state, a hot melt adhesive pressure (p) prevailing in the hot melt adhesive line (3, 3a, 3a') is reduced to a start-up pressure. is increasedwhich is higher than a working pressure associated with the performance in the second operating state, and the start-up pressure is reduced to the working pressure depending on time and / or on the number of hot melt adhesive applications carried out, wherein the device (1) can be operated in the second operating state such that the hot melt adhesive pressure (p) prevailing in the hot melt adhesive line (3, 3a, 3a') corresponds to the working pressure.

14. Device (1 ) according to claim 13, characterized in that the device has a pressure control circuit (RC) with at least one application pressure sensor (10, 10') connected to the control and / or regulating device (100) for detecting an application pressure of the hot melt adhesive prevailing at the application head (5, 5'). 12294 WO 15. Device (1) according to claim 13 or 14, characterized in that a foaming device (7) for applying a gas, in particular nitrogen, to the hot melt adhesive to produce a foam adhesive is arranged between the hot melt adhesive tank (2) and the at least one application head (5, 5'), wherein the foaming device (7) comprises at least one controllable and / or adjustable pump unit (14, 14'), preferably a multi-stage, controllable and / or adjustable pump unit (14, 14'), and a gas supply for applying the gas to the hot melt adhesive, wherein the pump unit (14, 14') is designed to convey the gas-treated hot melt adhesive to the at least one application head (5) under the hot melt adhesive pressure (p).

16. Device (1 ) according to claim 15 or 16, characterized in that the control and / or regulating device (100) is configured to act on the pump unit (14, 14') depending on the application pressure detected by means of the application pressure sensor (10, 10'). 12294 WO

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