Device and method for applying an adhesive to a substrate

Abstract

The invention relates to a device (100) for applying hot melt adhesive (120a) to a plurality of substrates (170), in particular packaging (170). The device (100) comprises an application unit (150) configured to apply an adjustable quantity of the hot melt adhesive (120a) in a layer (170a) to a substrate (170) being processed, which is moved relative to the application unit (150). Furthermore, the device (100) comprises a gloss sensor (160) configured to perform a plurality of gloss measurements at a plurality of locations on the layer (170a) of the hot melt adhesive (120a) on the substrate (170) being processed.The device (100) further comprises a control and evaluation unit (130) which is configured to adjust the adjustable quantity of hot melt adhesive (120a) for a subsequently processed substrate (170) based on the multitude of gloss measurements taken at the multitude of locations of the layer (170a) of the hot melt adhesive (120a) on the substrate (170) currently being processed. Furthermore, a corresponding method for applying hot melt adhesive (120a) to a multitude of substrates (170), in particular packaging (170), is described.

Description

[0001] The invention relates to a device and a method for applying a hot melt adhesive to a substrate, in particular a packaging.

[0002] In the production of shipping packaging, for example, for online retail, one or two strips of hot melt adhesive (also known as pressure-sensitive adhesive) are often applied to the flap of a corrugated cardboard box that is to be sealed. These adhesive strips are then covered with a silicone-coated paper. A tear strip can be added in addition to the adhesive. When the goods are packed, the silicone paper is removed from the outer adhesive strip, thus closing the shipping packaging. If the customer returns the goods, the original packaging can be sealed with the second adhesive strip. The pressure-sensitive adhesive, protected by the silicone strip, thus retains its functionality.

[0003] A device and method for applying a pressure-sensitive adhesive to a corrugated cardboard box with a final covering by a protective tape is described in EP0431144B1. The method comprises depositing the pressure-sensitive adhesive in a heated state from an application nozzle in contact with a surface of the corrugated cardboard box, and then applying a protective strip, such as siliconized paper, from a dispenser to the adhesive application area with or without pressure.

[0004] High demands are placed on the adhesive application. The adhesive layer must be sufficiently thick to compensate for any unevenness in the carton surface or to bridge the corrugated board's wave structure. A perfect application has a closed, homogeneous application surface with a smooth tear-off edge and should seal immediately without further pressure. This ensures perfectly sealed packaging and protects the transported goods from damage.

[0005] However, these stringent requirements often lead users to apply the hot melt adhesive with a layer that is far too thick for safety reasons. For corrugated cardboard shipping boxes, for example, layer thicknesses between 300 and 500 g / m² are applied. Given the often very large flaps of these corrugated cardboard shipping boxes, this leads to high costs. Applying a layer that is too thick above the required level thus leads to unnecessary additional costs and the associated economically and ecologically detrimental waste of valuable resources.

[0006] Against this background, it is the object of the present invention to provide an improved device and an improved method for applying a hot melt adhesive to a substrate, in particular a packaging, with a reduced hot melt adhesive consumption while maintaining the same adhesive effect of the hot melt adhesive.

[0007] According to a first aspect of the invention, the above object is achieved by a device for applying hot melt adhesive to a plurality of substrates, in particular packaging. The device comprises an application device configured to apply an adjustable amount of the hot melt adhesive in a layer to a currently processed substrate, which is moved relative to the application device along a transport direction. Furthermore, the device comprises a gloss sensor configured to perform a plurality of gloss measurements at a plurality of locations on the layer of hot melt adhesive on the currently processed substrate.The device further comprises a control and evaluation device which is designed to adjust the adjustable amount of hot melt adhesive for one or more subsequently processed substrates on the basis of the plurality of gloss measurements at the plurality of locations of the layer of hot melt adhesive on the currently processed substrate.

[0008] The device according to the first aspect of the invention is based on the finding that adhesive coatings generally have a higher gloss level than uncoated areas of a substrate, in particular a cardboard packaging, and thus the gloss level serves as a measure of whether or not the correct amount of adhesive has been applied to the area of ​​a substrate monitored by the gloss sensor device. Thus, an improved device for applying a hot melt adhesive to a substrate, in particular a packaging, is provided, with reduced hot melt adhesive consumption while maintaining the same adhesive effect of the hot melt adhesive.

[0009] According to one embodiment, the control and evaluation device is designed to determine a quantitative measure of the homogeneity of the thickness of the layer of the hot melt adhesive on the basis of the plurality of gloss measurements and to adapt the adjustable amount of the hot melt adhesive for a subsequently processed substrate if the quantitative measure of the homogeneity of the thickness of the layer of the hot melt adhesive exceeds or falls below a threshold value.

[0010] In one embodiment, the control and evaluation device is designed to process the plurality of gloss measurements at the plurality of locations of the layer of hot melt adhesive by means of a Fourier analysis and to adjust the adjustable amount of hot melt adhesive for a subsequently processed substrate on the basis of the plurality of gloss measurements processed by means of the Fourier analysis.

[0011] According to one embodiment, the gloss sensor device is designed to carry out the plurality of gloss measurements at the plurality of locations of the layer of hot melt adhesive on the currently processed substrate along the transport direction and / or transversely to the transport direction.

[0012] In one embodiment, the device further comprises a transport device which is designed to move the substrate along the transport direction relative to the application device and / or the gloss sensor device.

[0013] According to one embodiment, the application device is designed to apply the adjustable amount of hot melt adhesive to the substrate in the form of at least one strip-shaped layer. The application device can, for example, comprise a slotted nozzle, wherein the slot runs substantially perpendicular to the transport direction of the substrate.

[0014] In one embodiment, the device further comprises a flow sensor configured to determine the adjustable amount of hot melt adhesive supplied to the application device, and wherein the control and evaluation device is configured to adjust the adjustable amount of hot melt adhesive for a subsequently processed substrate based on the plurality of gloss measurements at the plurality of locations of the layer of hot melt adhesive on the currently processed substrate and on the amount of hot melt adhesive supplied to the application device. For example, the control and evaluation device can be configured to adjust the adjustable amount of hot melt adhesive for a subsequently processed substrate by adjusting a conveying speed of a hot melt adhesive conveying pump.

[0015] According to one embodiment, the gloss sensor device comprises one or more gloss sensors (also known as inline gloss sensors), wherein each gloss sensor is configured to perform the plurality of gloss measurements at the plurality of locations of the layer of hot melt adhesive on the currently processed substrate by means of a respective scanning beam and a respective reference beam.

[0016] In one embodiment, the device further comprises a device which is designed to apply a paper protective strip, in particular a siliconized paper protective strip, to the layer of hot melt adhesive on the currently processed substrate.

[0017] According to a second aspect of the invention, the above object is achieved by a method for applying hot melt adhesive to a variety of substrates, in particular packaging. The method comprises the following steps: applying an adjustable amount of the hot melt adhesive by means of an application device in a layer on a currently processed substrate, which is moved relative to the application device along a transport direction; Performing a plurality of gloss measurements at a plurality of locations on the layer of hot melt adhesive on the substrate currently being processed; and Adjusting the adjustable amount of hot melt adhesive for a subsequently processed substrate based on the plurality of gloss measurements at the plurality of locations of the hot melt adhesive layer on the currently processed substrate. Thus, an improved method for applying a hot melt adhesive to a substrate, in particular a packaging, is provided, with reduced hot melt adhesive consumption while maintaining the adhesive effect of the hot melt adhesive.

[0018] The invention is described in more detail below using exemplary embodiments and the figures. The figures show: Fig. 1 is a schematic representation of an apparatus for applying hot melt adhesive to a substrate according to one embodiment; and Fig. 2 is a flowchart showing steps of a method for applying hot melt adhesive to a substrate according to one embodiment.

[0019] In the following detailed description, reference is made to the accompanying figures, which form a part hereof, and in which is shown by way of illustration specific embodiments in which the invention may be practiced. It is understood that other embodiments may be utilized and structural or logical changes may be made without departing from the scope of the present invention. The following detailed description, therefore, is not to be taken in a limiting sense. Further, it is to be understood that the features of the various embodiments described herein may be combined with one another unless specifically indicated otherwise.

[0020] The aspects and embodiments of the present invention are described with reference to the figures, wherein like reference numerals generally refer to like elements. In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of one or more aspects of the present invention.

[0021] Fig. 1 is a schematic representation of an apparatus 100 according to the invention for applying hot melt adhesive 120a to a plurality of substrates 170, in particular packaging 170.

[0022] The device 100 comprises an application device 150, which is configured to apply an adjustable amount of the hot melt adhesive 120a in a layer 170a to a currently processed substrate 170, which is moved relative to the application device 150 along a transport direction 115. For this purpose, the device 100 further comprises a transport device 110, which may, for example, comprise conveyor belts, transport belts, and / or transport rollers and is configured to move the plurality of substrates 170 one after the other along the transport direction 115 relative to the application device 150.

[0023] In one embodiment, the application device 150 is configured to apply the adjustable amount of the hot melt adhesive 120a in the form of one or more strip-shaped layers 170a on the substrate 170.

[0024] At the Fig. 1, the device 100 further comprises a flow sensor 140, which is designed to determine the amount of hot melt adhesive 120a supplied to the application device 150 or to provide measured values ​​which enable the control and evaluation device 130, described in detail below, to determine the amount of hot melt adhesive 120a supplied to the application device 150.

[0025] In one embodiment, the application device 150 may be designed as a known hot melt system or part of a hot melt system. Fig. 1, this hot melt system comprises, in addition to the application device 150, a melting device 120 or a hot melt adhesive tank 120 for storing the hot melt adhesive 120a, as well as one or more heated conveyor hoses 122 for supplying the hot melt adhesive 120a from the hot melt adhesive tank 120 to the application device 150. The hot melt adhesive tank 120 can comprise a pump for supplying the hot melt adhesive 120a at an adjustable volume flow via the heated conveyor hoses 122 to the application device 150. In one embodiment, the application device 150 can comprise one or more heated adhesive application valves 150 for applying the hot melt adhesive 120a to the substrate 170 at a processing temperature, for example, between 120°C and 200°C.

[0026] Alternatively, the application device 150 of the apparatus 100 can be configured as a "melt-on-demand" hot melt system or as a part thereof, in which the adhesive 120a is first conveyed in solid, non-molten form via conveying lines to an adhesive application head or adhesive application valve, and is melted in or immediately before the adhesive application head or adhesive application valve and then applied to the substrate 170. In such a system, heated conveyor hoses can be dispensed with. According to one embodiment, the heated adhesive application valves of the application device 150 ensure the metering and positioning of the hot melt adhesive 120a on the substrate 170 via an electrically or electropneumatically actuated closure element and one or more nozzles 150a.

[0027] As already described above, the device 100 can comprise, in addition to the hot melt adhesive tank 120, the pump, which can be part of the hot melt adhesive tank 120, the heated conveyor hose 122 and the at least one adhesive application valve 150, the flow sensor 140, which according to one embodiment are part of a control circuit. The flow sensor 140 can be arranged in the melter 120 between the pump and the distributor of the melter 120, in the distributor itself, in the heated hose 122, in the flow direction of the adhesive 120a immediately before (as in Fig. 1) or in the adhesive application valve 150. The flow sensor 140 generates information about the flow rate or volume flow. A volume flow is understood to be the volume of a medium that moves through a cross-section within a unit of time. The flow sensor 140 can be a volume flow sensor 140 in the form of a gear or turbine flow meter. In a gear flow meter, the volume flow sensor 140 is designed in the form of a reverse-operating gear pump. The volume flow sensor 140 measures predetermined partial quantities of the adhesive through the toothing. For each partial quantity that is delivered by the rotary movement of the intermeshing teeth caused by the volume flow, an electrical pulse is emitted via the magneto-electric sensor 140 or another suitable sensor 140.Typically, the magnetoelectric sensor 140 is a differential field plate sensor located above the gear rim of one of the two measuring gears. It emits an electrical pulse for each tooth passing beneath it. In a turbine flowmeter 140, the adhesive is passed through a turbine driven by the turbine, whose rotation is detected.

[0028] According to one embodiment, the device 100 may further comprise a Fig. 1, which is designed to apply a paper protective strip, in particular a silicone-coated paper protective strip, to the layer 170a of the hot melt adhesive 120a on the currently processed substrate 170. Suitable silicone strip dispensers are marketed, among others, by ENPRO, Wilsum, Germany, under the trade name SPA. Such a silicone strip dispenser essentially consists of a dispenser and an application head.

[0029] Furthermore, the device 100 comprises a gloss sensor device 160, which is designed to carry out a plurality of gloss measurements at a plurality of locations or positions on the surface of the layer 170a of the hot melt adhesive 120a on the currently processed substrate 170.

[0030] In one embodiment, the gloss sensor device 160 is configured to perform the plurality of gloss measurements at the plurality of locations of the layer 170a of the hot melt adhesive 120a on the currently processed substrate 170 along the transport direction 115 and / or transversely to the transport direction 115. For this purpose, according to one embodiment, one or more gloss sensors 160 arranged in parallel can be provided, wherein each gloss sensor 160 is configured to perform the plurality of gloss measurements at the plurality of locations of the layer 170a of the hot melt adhesive 120a on the currently processed substrate 170 by means of a respective scanning beam and a respective reference beam.

[0031] Gloss is a visual perception that occurs when observing surfaces. The more directed the light is reflected, the more pronounced the gloss perception is. According to DIN EN ISO 2813 and DIN EN ISO 4816, the terms high-gloss, glossy, satin-gloss, semi-gloss, semi-matt, matt, and dull-matt are used for coating materials, whereas the terms high-gloss, satin-gloss, satin-matt or semi-matt, matt, dull-matt, deep matt or ultra-matt, and natural matt are used for varnishes and paints. The principle of gloss measurement is essentially based on the measurement of directed reflected light. Preferably, only one value is measured during gloss measurement, which represents a relationship between a reference and the measured reflection value of the hot melt adhesive. This has the advantage that the amount of data is small and only one value per measuring point needs to be considered in the evaluation.

[0032] A high-gloss surface reflects incident light only in the primary reflection direction, whereas matte surfaces also reflect light diffusely into all solid angles. The general rule is that the more evenly the light is scattered, the lower the intensity of the directional component and the more matte the surface appears.

[0033] According to one embodiment, the gloss sensor device 160 or each gloss sensor of the gloss sensor device 160 is configured to perform a gloss measurement by projecting an incident scanning light beam 161 onto the layer 170a at a specific angle, for example, using suitable optics 160a of the gloss sensor device 160, detecting at least the reflected scanning beam 162, and measuring its intensity. The measured gloss value can be compared with a reference standard (often a black glass or a polished ceramic plate with a very high reflectance). As already described above, according to one embodiment, the gloss sensor device 160 is configured to operate with a reference light beam as a standard to which the gloss measurement is related. The reference signal can be generated, detected, and evaluated in the gloss sensor device 160.For this purpose, the gloss sensor device 160 can have two specially arranged receivers that detect the diffusely reflected and the specular light. The ratio of the signals of the diffusely reflected light to the specular light is a measure of the gloss level.

[0034] In one embodiment, the gloss sensor device 160 may comprise at least a part of the control and evaluation device 130 described in detail below or may transmit the gloss measurement data to the control and evaluation device 130 via the control and / or data line 155 (as in the embodiment of Fig. 1), which carries out the evaluation. The control and evaluation device 130 can also be part of the adhesive application system 120, 150, for example as part of the melter control or a pattern control that serves to control the adhesive application valves 150 and the pump. As will be described in more detail below, according to one embodiment, the gloss sensor device 160 is part of a control loop that serves to regulate the amount of adhesive 120a applied to the substrates 170. The gloss sensor device 160 can also transfer set values ​​directly or via an intermediate control with an optional evaluation of the measured data or set values ​​to a frequency converter with integrated control, which serves to adjust the motor speed of the pump of the adhesive melter 120.

[0035] As already described above, the device 100 further comprises a control and evaluation device 130, for example a microprocessor, which is connected to the hot melt adhesive tank 120, the flow sensor 130, the application device 150, and the gloss sensor device 160 via control and / or data lines 125, 135, 145, 155. As will be described in more detail below, the control and evaluation device 130 is configured to adjust the adjustable amount of the hot melt adhesive 120a for a subsequently processed substrate 170 based on the plurality of gloss measurements by the gloss sensor device 160 at the plurality of locations of the layer 170a of the hot melt adhesive 120a on the currently processed substrate 170.

[0036] In one embodiment, the control and evaluation device 130 is designed to adapt the adjustable amount of the hot melt adhesive 120a for a subsequently processed substrate 170 based on the plurality of gloss measurements at the plurality of locations of the layer 170a of the hot melt adhesive 120a on the currently processed substrate 170 and based on the amount of the hot melt adhesive 120a supplied to the application device 150, which amount can be determined by means of the flow sensor 140 as already described above.

[0037] In one embodiment, the control and evaluation device 130 is configured to determine a quantitative measure of the homogeneity of the thickness of the layer 170a of the hot melt adhesive 120a based on the plurality of gloss measurements and to adjust the adjustable amount of the hot melt adhesive 120a for a subsequently processed substrate 170 if the quantitative measure of the homogeneity of the thickness of the layer 170a of the hot melt adhesive 120a exceeds or falls below a threshold value.

[0038] As already described above, according to one embodiment, the device 100 implements a closed loop, i.e., a process control technique in which feedback from the process output is used to adjust the variables that affect the output. In contrast, an open loop system is a process control technique that does not use output feedback. In the present invention, the output variable of the closed loop is the amount of adhesive applied to a respective substrate 170. As already described above, this output variable can be adjusted or changed, for example, by controlling the pump of the hot melt adhesive tank 120 by the control and evaluation device 130.

[0039] The input variables of the closed control loop implemented by device 100 are the gloss measurements recorded by gloss sensor device 160 (as well as, if applicable, the volume flow data recorded by flow sensor 140) or variables derived therefrom. These are compared with specified values ​​in the control system implemented by control and evaluation device 130. In the event of deviations, the control and evaluation device 130 adjusts the applied adhesive quantity or the conveyed volume flow.

[0040] According to one embodiment, the control and evaluation device 130 is configured to derive default values ​​for the control loop, consisting of the flow meter 140 and pump control, from the gloss measurements recorded by the gloss sensor device 160 or the variables derived therefrom. For example, the gloss sensor device 160 can detect increased unevenness of the adhesive layer 170a on the surface of the corrugated cardboard substrate 170. From this, the control and evaluation device 130 can derive an increased adhesive requirement. The adjustment is then performed by a new default value for the control of the adhesive delivery (pump and control) and the flow meter 140.The measured values ​​of the flow meter 140 are compared with the new specification and, in the event of a deviation, the flow is readjusted until the measured values ​​of the flow meter 140 agree with the specification values ​​within a specified tolerance band, which can also be zero.

[0041] An alternative control loop implemented by the device 100 can consist of at least one pressure sensor and a pump controller. The pressure sensor can be located downstream of the pump in the direction of adhesive flow, for example, in the melter 120 and / or immediately upstream of or in the adhesive application valve 150. In this case, the control loop regulates to a predetermined pressure value calculated based on the gloss measurements.

[0042] In principle, the measured values ​​of the gloss sensor device 160 of each individual corrugated board substrate 170 can be recorded and used as the basis for control. However, the values ​​can also be used only if a certain threshold is exceeded or if a permanent change across multiple substrates 170 or a trend in one direction is detected.

[0043] In one embodiment, the control can be carried out by the control and evaluation device 130 as adaptive control in order not to immediately execute control in the event of individual deviations in a single substrate. Furthermore, adaptive control helps to avoid overshooting the target, for example, when reducing the amount of adhesive. If the entire control step is carried out in one go, there is a risk that too little adhesive will be applied. Typical steps in the adaptation process are identification, which can be done indirectly or directly, and the decision-making process, which changes the adjustable parameters during the process flow via a modification stage. Preferably, the adaptation is carried out in small steps, and the response is determined based on the surface measurement values, from which further adaptation steps are derived to avoid overshooting.If the adhesive application is too low, according to one embodiment, the control and evaluation device 130 can select an adhesive quantity that is greater than the calculated value to ensure secure bonding. The adhesive quantity can then be gradually reduced.

[0044] As already described above, the gloss sensor device 160 is configured to collect gloss measurement data over a measuring path, which reflects the surface unevenness of the adhesive layer 170a located on the substrate 170. The surface unevenness is essentially characterized by the wave pitch of the corrugated cardboard substrate 170. This wave pitch generates a periodic signal, since the waves and valleys follow each other at fixed intervals within narrow limits, and the spacing of the waves is determined inside the corrugated cardboard substrate 170. According to one embodiment, the control and evaluation device 130 is therefore configured to process the plurality of gloss measurements at the plurality of locations on the layer 170a of the hot melt adhesive using a Fourier analysis and, based on the plurality of gloss measurements processed using the Fourier analysis, to adjust the adjustable quantity of the hot melt adhesive 120a for a subsequently processed substrate 170.

[0045] However, those skilled in the art will recognize that the gloss measurement data provided by the gloss sensor device 160 can also be evaluated by the control and evaluation device 130 using other data processing methods based on the plurality of gloss measurements. For example, the control and evaluation device 130 can be configured to use the range between the highest gloss measurement value and the lowest measured gloss value as a benchmark for the potential adjustment of the adhesive quantity.

[0046] In one embodiment, the control and evaluation device 130 is configured to subject the gloss measurement data provided by the gloss sensor device 160 to an outlier analysis in order to exclude extreme measured values, which may arise, for example, from holes or other small defects in the surface, from the evaluation. The outlier test can refer to the entirety of the acquired gloss measurement data, or the entirety of the gloss measurement data can be divided into two subgroups, in which a respective outlier analysis is performed by the control and evaluation device 130. The subgroups can be determined based on the mean or median of the data, with one group being below and one group being above. Outlier tests can be used that assume normally distributed measured values.This is possible because, based on the waveform of the corrugated cardboard substrate 170, an approximately normal distribution can be assumed. An example of such an outlier test is the Grubbs or Nalimov method. For two subgroups, the mean or median of the measured values ​​can be calculated for each subgroup. The range between the mean or median of the subgroups then represents the degree of surface unevenness. The median is preferred because it is less sensitive to distortions caused by outliers.

[0047] According to a further embodiment, the control and evaluation device 130 can be configured to implement at least one characteristic curve or calculation formula by means of which the control and evaluation device 130 can determine or calculate the required adhesive application per unit area or the necessary feed rate per unit time based on the gloss measurement data provided by the gloss sensor device 160. In one embodiment, the control and evaluation device 130 can be connected to a sensor that supplies measurement data representative of the production speed of the device 100. The sensor can be a rotary encoder installed in the device 100. The speed can also be derived from product detection sensors that detect, for example, the leading edge of a batch of corrugated cardboard substrates 170.The control and evaluation device 130 is preferably connected to the product detection sensor, which detects the beginning of an individual corrugated cardboard substrate 170 as it passes through the device 100.

[0048] According to one embodiment, characteristic curves or formulas are implemented in the control and evaluation device 130, which comprise the relationship between the delivery rate or speed or stroke cycles of the pump or the working pressure of a pneumatically driven pump and the amount of adhesive applied per unit area or time.

[0049] In one embodiment, the control and evaluation device 130 comprises a display unit, in particular a display screen, or is directly or indirectly connected to such a display unit. The display unit displays the applied adhesive quantity per unit area and / or per individual substrate 170. Furthermore, the display unit can display the amount of adhesive used per unit time and / or the fill level of the tank 120 in order to provide the operator with information on refilling the adhesive 120a in the tank 120.

[0050] Furthermore, the control and evaluation device 130 can comprise or be connected to an input unit, for example a touch pad, which makes it possible to adapt the default value of the control loop implemented by the device 100.

[0051] Preferably, a safety factor can be entered, such as a positive quantity value, which is added to the quantity of adhesive calculated by the control and evaluation device 130.

[0052] Fig. 2 is a flowchart showing a method 200 for applying hot melt adhesive 120a to a plurality of substrates 170, in particular packaging 170. The method 200 comprises the steps of: applying 201 an adjustable amount of the hot melt adhesive 120a by means of the application device 150 in a layer 170a on a currently processed substrate 170, which is moved relative to the application device 150 along the transport direction 115; Performing 203 a plurality of gloss measurements at a plurality of locations of the layer 170a of the hot melt adhesive 120a on the currently processed substrate 170; and adjusting 205 the adjustable amount of the hot melt adhesive 120a for a subsequently processed substrate 170 based on the plurality of gloss measurements at the plurality of locations of the layer 170a of the hot melt adhesive 120a on the currently processed substrate 170. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] EP 0431144B1

[0003]

Claims

[1] Device (100) for applying hot melt adhesive (120a) to a plurality of substrates (170), in particular packaging (170), the device (100) comprising: an application device (150) which is designed to apply an adjustable amount of the hot melt adhesive (120a) in a layer (170a) on a currently processed substrate (170) which is moved relative to the application device (150) along a transport direction (115); a gloss sensor device (160) which is designed to perform a plurality of gloss measurements at a plurality of locations of the layer (170a) of the hot melt adhesive (120a) on the currently processed substrate (170); and a control and evaluation device (130) which is designed to adapt the adjustable amount of the hot melt adhesive (120a) for a subsequently processed substrate (170) on the basis of the plurality of gloss measurements at the plurality of locations of the layer (170a) of the hot melt adhesive (120a) on the currently processed substrate (170). [2] Device (100) according to claim 1, wherein the control and evaluation device (130) is designed to determine a quantitative measure of the homogeneity of the thickness of the layer (170a) of the hot melt adhesive (120a) on the basis of the plurality of gloss measurements and to adapt the adjustable amount of the hot melt adhesive (120a) for a subsequently processed substrate (170) if the quantitative measure of the homogeneity of the thickness of the layer (170a) of the hot melt adhesive (120a) exceeds or falls below a threshold value. [3] Apparatus according to claim 1 or 2, wherein the control and evaluation device (130) is designed to process the plurality of gloss measurements at the plurality of locations of the layer (170a) of the hot melt adhesive (120a) by means of a Fourier analysis and to adjust the adjustable amount of the hot melt adhesive (120a) for a subsequently processed substrate (170) on the basis of the plurality of gloss measurements processed by means of the Fourier analysis. [4] Device (100) according to one of the preceding claims, wherein the gloss sensor device (160) is designed to carry out the plurality of gloss measurements at the plurality of locations of the layer (170a) of the hot melt adhesive (120a) on the currently processed substrate (170) along the transport direction (115) and / or transversely to the transport direction. [5] Device (100) according to one of the preceding claims, wherein the device (100) further comprises a transport device (110) which is designed to move the substrate (170) along the transport direction (115) relative to the application device (150) and / or the gloss sensor device (160). [6] Device (100) according to one of the preceding claims, wherein the application device (150) is designed to apply the adjustable amount of the hot melt adhesive (120a) in the form of at least one strip-shaped layer (170a) on the substrate (170). [7] Device (100) according to one of the preceding claims, wherein the device (100) further comprises a flow sensor (140) which is designed to determine the amount of hot melt adhesive (120a) supplied to the application device (150), and wherein the control and evaluation device (130) is designed to adapt the adjustable amount of hot melt adhesive (120a) for a subsequently processed substrate (170) on the basis of the plurality of gloss measurements at the plurality of locations of the layer (170a) of hot melt adhesive (120a) on the currently processed substrate (170) and on the basis of the amount of hot melt adhesive (120a) supplied to the application device (150). [8] Device (100) according to one of the preceding claims, wherein the gloss sensor device (160) comprises one or more gloss sensors (160), wherein each gloss sensor (160) is designed to carry out the plurality of gloss measurements at the plurality of locations of the layer (170a) of the hot melt adhesive (120a) on the currently processed substrate (170) by means of a respective scanning beam and a respective reference beam. [9] Device (100) according to one of the preceding claims, wherein the device (100) further comprises a device which is designed to apply a paper protective strip, in particular a siliconized paper protective strip, to the layer (170a) of the hot melt adhesive (120a) on the currently processed substrate (170). [10] Method (200) for applying hot melt adhesive (120a) to a plurality of substrates (170), in particular packaging (170), the method (200) comprising: Applying (201) an adjustable amount of the hot melt adhesive (120a) by means of an application device (150) in a layer (170a) on a currently processed substrate (170), which is moved relative to the application device (150) along a transport direction (115); Carrying out (203) a plurality of gloss measurements at a plurality of locations of the layer (170a) of the hot melt adhesive (120a) on the currently processed substrate (170); and Adjusting (205) the adjustable amount of hot melt adhesive (120a) for a subsequently processed substrate (170) based on the plurality of gloss measurements at the plurality of locations of the layer (170a) of hot melt adhesive (120a) on the currently processed substrate (170).

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