BR102017014424B1 - INSPECTION DEVICE AND METHOD FOR INSPECTING AN ADHESIVE PATTERN ON A SUBSTRATE - Google Patents

Abstract

Inspection devices and methods for inspecting an adhesive pattern on a substrate are described. The inspection device includes at least one sensor having a heat sensor head for detecting a pattern of the adhesive microsphere, an enclosure for housing the heat sensor head, and a controller. Reference data representing a desired adhesive pattern is initially provided to a controller. A predetermined tolerance range for the desired adhesive pattern is also provided to the controller. An adhesive microsphere is discharged onto a substrate from a nozzle. A pattern of the discharged adhesive microsphere is then detected by the sensor when the substrate moves. Signals representing the detected pattern are received from the sensor in the controller. Finally, the signals representing the detected adhesive pattern are compared with the tolerance range of the desired adhesive pattern.

Description

[0001] The invention relates to a method for inspecting an adhesive pattern on a substrate. Furthermore, the invention relates to an inspection device for inspecting an adhesive pattern on a substrate. The invention further relates to an applicator head comprising a basic body, a nozzle for discharging an adhesive and an inspection device of the aforementioned art.

[0002] Adhesive patterns are discharged from applicator heads and deposited on substrates for several reasons. In particular in the packaging industry, adhesive patterns are deposited on a substrate in order to produce packaging material. Specific examples of these packaging materials are plastic sheets or fiberboard. Packaging materials are typically fed into a machine as substantially flat elements (also referred to below as substrates). The fluid, primarily hot-melt adhesive, is then applied along one or more tracks to various areas of the substrate in a process to discharge a fluid through an applicator head. After applying the adhesive, the packaging materials are either filled with a product or remain empty. The areas to which the adhesive was previously applied are then folded along defined edges and pressed onto corresponding areas. The applied adhesive causes the areas to adhere to each other.

[0003] The application described above refers to mass production therefore, in addition to increasing the efficient use of time, efforts to produce improvements are also centered at all times on reducing the amount of material required for production.

[0004] Therefore, it is known to apply an intermittent segment pattern of short pulses of the adhesive onto substrates, rather than applying continuous micro-beads of adhesive, in order to provide an adequate adhesive effect, while using a reduced amount of fluid or adhesive.

[0005] In EP 2 638 978 A1, there is known a method for transforming a primary discharge signal for controlling an applicator head into a secondary discharge signal, the secondary discharge signal having a plurality of successive signal portions spaced between si, which are each determined as part of the length of the primary signal, the total length of which is less than the length of the primary signal. Using this method, the primary discharge signal, which may indicate, for example, a continuous adhesive microsphere, is transformed into a so-called "stitched" signal for stitching an adhesive pattern, which consists of a plurality of successive microsphere portions. , spaced apart.

[0006] By carrying out these methods, the operation moves closer to the limit, and the need to verify that the correct amount of adhesive is applied becomes increasingly important. Transporting products that are defective due to incorrect adhesive application needs to be avoided to avoid costly returns and reputational damage. Today, adhesive verification can only be done with the use of complex and expensive systems that are not easily integrated and not well suited to the requirements of the packaging market, in particular in terms of space, short time for integration into existing systems and ease of use. Systems must be configured for each application and must be programmed for each new pattern, so changes in machine speed can already cause false detection and inspection of an adhesive pattern.

[0007] Therefore, it is an object of the invention to provide an inspection method and a device for carrying out that method, which solves at least some of the problems mentioned above and which is simple, less complex, easy to use and which can be used with machines existing.

[0008] In a first aspect of the invention, the object is achieved with a method of the initially specified type, comprising the steps of: providing reference data representing a desired adhesive pattern in a controller; provide a stored, predetermined tolerance range for the desired adhesive pattern in the controller; discharging an adhesive microsphere onto a substrate from a nozzle; detecting a pattern of the adhesive microsphere discharged onto the substrate, when the substrate moves, by means of a sensor arrangement; receiving signals representing the detected pattern from the sensor arrangement in the controller; and comparing said signals representing the detected adhesive pattern with the tolerance range of the desired adhesive pattern.

[0009] The invention is based on the idea that as less adhesive is used for a substrate to glue the substrate to another surface, it is not sufficient to just control a discharge nozzle by means of a direct power signal, but that it is necessary to inspect the adhesive pattern discharged onto the substrate. The invention makes use of the idea that it is beneficial to inspect the discharged pattern directly after application and not at the end of the process, when, for example, the packaging is already folded and the edges are glued together.

[0010] The main idea of the invention is that the detection method can be used autonomously and that no teaching button is required to teach a desired adhesive pattern. The method is preferably carried out by means of an inspection device of the second aspect of the invention. The method is based on the idea that the desired adhesive pattern is the pattern that is discharged onto the substrate in the target state under nominal conditions. This desired sticker pattern that the sensor array must detect in the target state is stored in the controller. Additionally, a predetermined tolerance range for the desired adhesive pattern is stored in the controller. When the pattern of the discharged adhesive microsphere is detected, signals, provided by the sensor arrangement, representing this detected pattern, are compared with the tolerance range of the respective desired adhesive pattern, via the controller. When it is determined that the detected adhesive pattern is within this tolerance range, the detected adhesive pattern is identified as being congruent with the adhesive pattern.

[0011] Congruent in this case means that the standard is within predefined tolerances, which can be adjusted manually, or which can be determined through a controller based on process parameters. Preferably the method is carried out with the use of an inspection device, according to at least one of the preferred embodiments explained below, of an inspection device according to the second aspect of the invention. It is to be understood that the inspection device of the second aspect of the invention and the method of the first aspect of the invention comprise identical and similar features which are defined in particular in the dependent claims. Heretofore, reference is made to the description below of the second aspect of the invention in relation to to the inspection device.

[0012] In particular, the length of the sticker pattern, and/or the length of the single microspheres of the sticker pattern are determined and compared to a desired length of the pattern and/or a desired length of the single microspheres of the sticker pattern. The length of the adhesive pattern is measured in the machine direction, that is, the direction of travel of the substrate. In general, there are different possibilities for determining length. On the one hand, it is preferred to determine, through measurement and/or calculation, a cumulative length of the discharged adhesive pattern, which is the cumulative length of all microspheres and microsphere portions of the discharged adhesive pattern. On the other hand, it is also possible to measure the total length, that is, the length from the leading edge of the first microsphere in the pattern to the trailing edge of the last microsphere in the pattern. Furthermore, it is also possible to determine, through measurement and/or calculation, pre or post pattern, which is the length of a microsphere, which extends beyond the desired leading edge of a desired adhesive pattern and/or the trailing edge. of a desired sticker pattern. All such measurements and/or determinations are preferred and performed with the present invention.

[0013] According to a first preferred embodiment, the predetermined tolerance range of the desired adhesive pattern is calculated using pre-stored typical values for a specific application case. In general, dispensing devices are designed and configured for a specific application by a customer and for these typical application cases, typical values are known that represent typical and acceptable deviations from a desired adhesive standard. For example, it is known what level of thermal radiation a microsphere produces when it is discharged at 140, 150 or 160°C, and has a width of 3 mm, for example. These values can be used to calculate the predetermined tolerance range for a desired thermal radiation of the adhesive microsphere. Furthermore, for example, the nozzle opening and closing reaction times under typical operating conditions for specific dispensers, such as Nordson Corporation's MiniBlue SP solenoid, are experimentally determined and therefore known. This range of reaction times can also be used to calculate the tolerance range. An exemplary calculation could then be to calculate a tolerance range of +/- 2 mm in microsphere length at an application speed of 60 m/min given a known range of opening and closing reaction times of 2 ms. .

[0014] Furthermore, it is optional to calculate the predetermined tolerance range using pre-detected values from an exemplary application case. These pre-detected values are not necessarily pre-detected by the manufacturer of the dispensing apparatus or inspection device, but can also be pre-detected by an operator when adjusting the device for an application case. For example, under known conditions, specific patterns are downloaded that are manually determined to be acceptable and thus congruent with a desired adhesive pattern. The values detected in these cases can be used to calculate the predetermined tolerance range. For example, average values that are detected in three samples are used to calculate the average of the three discharge patterns. This average value can be used to determine a new desired adhesive pattern and the predetermined tolerance range can be adjusted, for example, to 4.9 msec +/- 5%.

[0015] It is preferred that the step of detecting a pattern of the adhesive microsphere is carried out by detecting heat radiated from the adhesive microsphere. In this way, the pattern is detected in a non-contact manner and not based on visual inspection methods, but using wavelengths of radiation that are in a non-visual range.

[0016] In another preferred embodiment, the pre-stored and/or pre-detected values comprise at least one signal intensity value, which represents threshold values for the detected signals expected by said sensor arrangement when detecting the pattern of discharged adhesive microsphere. In particular, when using infrared sensors for the sensor array, these sensors detect a specific infrared radiation at all times. When a microsphere is detected, the radiation increases rapidly, as the microsphere is normally discharged with heat of around 150 °C and thus the signal intensity increases rapidly when a microsphere discharge is discharged.

[0017] It should be understood that the term "signal" can also refer to derivatives of signals or higher order derivatives, and is not limited to the single original source itself.

[0018] In a particularly preferred embodiment, detecting the pattern of the discharged adhesive microsphere comprises the steps of: determining by the controller an intensity or rate of change in the intensity of a value detected by the sensor arrangement; comparing by the controller the intensity or rate of change in intensity with the value or intensity of the rate of change in intensity or a respective limit value stored in the controller; and determining by the controller that a microsphere edge is present, when the intensity of the rate of change in the intensity signal exceeds the threshold value stored in the controller. When a substrate having an adhesive pattern discharged onto it approaches the sensor array, the signal intensity measured by the sensor array increases. Preferably, the rate of change of this changed signal intensity is determined and compared to a pre-stored rate of change value. The pre-stored rate of change value is endowed with a tolerance band. When the rate of change determined by the controller based on the detected changed intensity value is within this tolerance range, a microsphere edge is detected. When the value is increasing, it is indicative for a leading edge of a microsphere and when the value is decreasing, it is indicative for the trailing edge of a microsphere.

[0019] Preferably, the signal intensity rate of the change value or the respective threshold value is scaled by the controller in dependence on a substrate speed and/or in dependence on a cooling rate factor. The cooling rate of the discharged adhesive is dependent on the ambient temperature, airflow, and heat capacity of the discharged adhesive. When the adhesive is discharged at a low temperature or when the ambient temperature is high, the rate of change of the infrared radiation detected when the substrate approaches the sensor array is lower than in cases where the adhesive is discharged at a high temperature. Therefore, the rate of change value is preferably to scale. The same is true for substrate speed. When the substrate velocity is high, the rate of change of the intensity measured by the sensor array is also high. Therefore, it is preferred to scale the pre-stored rate of change value or the predetermined tolerance range for this value. This can be done automatically based on known relationships between these values.

[0020] In a preferred embodiment the rate of change of the intensity signal is passed through a low, high and/or bandpass filter to avoid intensity changes caused by sensor noise or environmental conditions that occur at rates atypical for onset/ end of an adhesive microsphere leading to false positive edge detection. This increases the robustness of the method.

[0021] According to another preferred embodiment, the method comprises the steps of: determining by the controller a displacement speed and the position of the substrate edge, and determining the displacement speed and the position of the substrate edge is carried out using a speed sensor of the sensor arrangement, comprising the steps of: determining by the controller a rate of change in the intensity of a value detected by the speed sensor; comparing by the controller the rate of change in intensity with a threshold pre-stored in the controller; and determining by the controller that a substrate edge is present when the rate of change in intensity exceeds the threshold. This can be done using two infrared sensors that detect the same microsphere and are moved relative to each other in the direction of the machine. When the machine direction displacement of these two infrared sensors is known, the displacement speed of the substrate can be determined. Alternatively, the speed sensor comprises two photocells that detect the edge of the substrate by evaluating the light radiation received. Preferably, the time gap between edge detection in the first photocell and second photocell is determined, and when the distance between the photocells in the machine direction is known, the speed can be calculated. The substrate is considered present until the next edge is detected, and an additional velocity measurement can be performed on that edge and used in conjunction with the first to provide a more accurate average velocity over the length of the substrate.

[0022] Alternatively or additionally, the method comprises the step of: determining the displacement speed of the substrate comprising detecting a microsphere, in particular, a leading edge of a microsphere, in a first position with a first sensor head, detecting the microsphere, in particular, the leading edge of the microsphere in a second position with a second sensor head, determine the time difference between the first and second detection, calculate the displacement speed based on the time difference and the displacement. positioning of the two sensor heads in the direction of movement.

[0023] Alternatively or additionally, the displacement speed is determined using an optical detector, preferably at least two closely spaced receivers, i.e., photocells, arranged to detect a leading edge and/or trailing edge of a substrate. Preferably, detection of the leading edge and/or the trailing edge of the substrate is done by detecting a rate of change in the intensity detected, for example, by the photocell. If this intensity exceeds a predetermined minimum value, it is considered a substrate edge. By comparing the time between detection at the first and second receivers, the speed of this edge can be calculated. The substrate is considered present until the next edge is detected. The predetermined minimum value can be pre-stored in a controller memory and can be derived on an experimental basis using actual production line configuration and actual environmental conditions. Due to this method, a measurement of the substrate speed of a rotary encoder, as is known in the prior art, is no longer necessary.

[0024] In another preferred embodiment of the invention, the method comprises the steps of: receiving a discharge signal from a control unit of a nozzle for discharging the adhesive; determine by the controller the desired pattern based on the received discharge signal; When the nozzle discharge signal pattern is known, this is a simple way to adjust a desired pattern. When the distance between the sensor and the nozzle is known, as well as the displacement speed of the substrate, it can be estimated at which moments, and at which points, an adhesive microsphere should be detected. On the received discharge signal, which can be intercepted by the controller, predetermined tolerances, preferably at least in the width and length direction, can be applied to determine the desired pattern. Due to this method, a learn button as known in the prior art is no longer necessary to teach a desired pattern to a machine.

[0025] According to another preferred embodiment, the step of determining the desired pattern comprises the steps of: calculating a desired microsphere start time and microsphere end time, using at least one predetermined delay value pre-stored in the controller. When the discharge signal is known and/or intercepted, and additionally, the geometric relationship between the nozzle, the substrate and the inspection device, in particular, the heat sensor or heat sensor heads are known, the adhesive pattern desired microsphere start time and microsphere end time can be calculated. The delay values in this case are, for example, the delay for a solenoid coil energization, delay for air flow into the adhesive valve module, delay for adhesive flow out of a module at the nozzle tip, delay for adhesive leakage from nozzle tip to substrate, delay for substrate moving to sensor head. All these delay values must be included in the calculation when the discharge signal is intercepted.

[0026] In a preferred embodiment, the method additionally comprises the steps of: determining a background heat when no substrate is present, comparing by the controller the determined background heat with a heat detected when a substrate and/or microsphere is present. Preferably, the determined background heat is stored in a memory in the controller and the stored background heat is used when the sticker pattern is detected. This means that it is not necessary for the sensor arrangement to measure absolute values of heat, it is sufficient to measure the rate of change, or a threshold between the background heat and the actual measured heat. Additionally, a heat threshold can be determined using background heat and when a heat above the threshold heat is measured, it is determined that an adhesive microsphere is present. When the threshold is reached, this position is detected as a start or an end of a microsphere, depending on whether it is a rising or falling edge, as discussed above.

[0027] Preferably, the step of detecting the pattern of the adhesive microsphere comprises detecting a width of the microsphere. This width can be detected using two or more infrared sensors arranged adjacent to each other, perpendicular to the direction of the machine. Preferably, the tolerance range comprises a width tolerance, the width tolerance being dependent on the travel speed of the substrate. When the substrate moves faster, the microsphere will typically have a smaller width when the discharge speed is kept constant. Therefore, the tolerance is also ideally scaled by speed and stored. This speed factor can be determined experimentally.

[0028] According to another preferred embodiment, the method comprises the steps of: providing a centerline tolerance range of the desired adhesive pattern; calculate a center line of the detected pattern; and compare the calculated centerline with the centerline tolerance band. The centerline can be calculated when the width of the discharge sticker pattern is known. This centerline, in accordance with this embodiment, is compared to a tolerance range of the centerline of the desired adhesive pattern. Due to these specific method steps, it is possible to determine whether a displacement in a direction perpendicular to the machine direction of the discharged adhesive pattern is within tolerance or not.

[0029] Furthermore, it is preferred that the method comprises the step of: calculating an area of the substrate that is covered by the microsphere. This area is called the microsphere area. By knowing the length and width of a microsphere, the area of the microsphere can also be calculated and it is possible to determine whether this microsphere area is within the predetermined tolerance range of a microsphere area of the substrate. This helps determine if enough adhesive is discharged to satisfy a specific application requirement.

[0030] In another preferred embodiment, the method comprises the steps of: providing a tolerance for a maximum space between two microspheres of the desired adhesive pattern; calculate a gap between the two microspheres of the detected pattern; and compare the calculated span with the tolerance for a maximum span. Preferably, when the calculated span is greater than the tolerance for the maximum span, a faulty signal is output. This measurement can be called a Max Gap measurement. The idea is that there is a maximum distance or gap allowed within the adhesive pattern that still meets the process requirements. This maximum distance is different for each application and also for each type of adhesive pattern that is used. Preferably, the method also comprises selecting between a high tolerance for a maximum gap between two microspheres of the desired adhesive pattern and a low tolerance for a maximum gap between two microspheres of the desired adhesive pattern. High tolerance is ideally selected when it is acceptable that even one internal microsphere of the adhesive pattern can be completely missing, and a portion of another internal microsphere of the pattern can be missing from the pattern and still pass the Max Gap check. Low tolerance for the maximum gap between two microspheres of the desired adhesive pattern is preferably selected when it is acceptable that there can be only a portion of a microsphere missing and still pass the Max Gap check. Preferably, this measurement is not cumulative , then any microsphere that is detected restarts the beginning of the Max Gap measurement, until the microsphere ends or there is a Max Gap failure.

[0031] In another preferred embodiment, also a thermal intensity of the microsphere area is used as a verification criterion. Thus, the method preferably comprises the steps of: providing a tolerance for a thermal intensity value of the desired area; measuring or calculating a thermal intensity value of the calculated area of the substrate that is covered by the microsphere; and compare the thermal intensity value of the calculated area with the tolerance for the thermal intensity value. This value can also be called intensity over area. This thermal intensity provides an indication of whether the adhesive temperature, and/or the amount of adhesive discharged is correct for applying the desired adhesive bond. If the thermal intensity value is too high, it is an indication that the adhesive temperature is too high and/or too much adhesive is discharged onto the substrate. Since this value is dependent on the desired area of the substrate that is covered by the adhesive, it is preferable that this area is measured and/or calculated in advance. In another aspect of the invention, or a preferred embodiment of the method, the above problem is solved by a method for inspecting an adhesive pattern on a substrate, comprising the steps of: providing a stored and predetermined tolerance range for a sticker pattern on a controller; receiving a discharge signal from a control unit of a nozzle for discharging the adhesive into the controller; determine by the controller the desired pattern based on the discharge signal received; receiving by the controller, a change in the discharge signal and/or receiving by the controller a discharge signal for the first time; and setting the tolerance range to the desired standard for a predetermined learning range. Preferably, the method comprises the steps of determining a change in the discharge signal and/or determining a discharge signal for the first time, and subsequently entering a learning mode. In such a learning mode, the step of setting a tolerance value to the desired standard for a predetermined learning value is preferentially performed. When it is determined that the discharge signal no longer matches the pattern of the previous discharge signal, or a discharge signal is detected for the first time, for example, when the method is first run or the machine is started, the discharge mode learning is inserted. The learning mode is preferably active for a predefined number of patterns and/or for a predefined period of time. The learning mode is used to adapt or adjust the inspection method and/or the inspection device of the second aspect described below, in particular, the inspection device controller, to an automatically changed discharge signal. Also, in this specific embodiment, it makes It is apparent that no teach button is necessary. Based on a change in the discharge signal and/or determining a discharge signal for the first time, the learn mode is entered and not due to an operator pressing the learn button.

[0032] The size of the tolerance value in the learning mode is preferably based on pre-stored values that correspond to predetermined sticker patterns, in particular, based on experimental data of typical sticker patterns. The learning tolerance value should be chosen so that the majority of the downloaded adhesive patterns are within the tolerance range during learning mode.

[0033] The preferred method further comprises the steps of: comparing a detected sticker pattern with the previously detected sticker pattern, and determining whether the deviation and/or the rate of deviation between the detected pattern, since the change in discharge signal and/or the discharge signal has been determined is within a predefined tolerance. According to this embodiment, which is useful in particular when the learning mode is entered, the currently detected sticker pattern is compared with the previously detected sticker pattern. Preferably, the currently detected sticker pattern is compared to two or more currently detected sticker patterns, as a change in the pattern has been determined and/or a learning mode has been entered. The deviation between the current and previous standard is determined. Additionally or alternatively, a deviation rate between the current standard and previously detected standards is determined. After the deviation and/or deviation rate has been determined, it is further determined whether this deviation and/or deviation rate is within a predefined tolerance. This allows you to check whether the sticker pattern has detected cycles or converges so that a stable output is achieved. In the event it is determined that the deviation and/or deviation rate is not within the predefined tolerance, a pattern failure signal may be generated. Preferably, the number of previously downloaded standards that is analyzed is in the range of 2 to 10, preferably 2 to 5, particularly preferably 3. Preferably, the average values of these last 3 downloaded standards are used.

[0034] In another preferred embodiment, the method comprises the steps of: achieving a predetermined number of N-1 detected adhesive patterns once the change in the discharge signal and/or the discharge signal has been determined, using the detected N pattern as the desired pattern and/or evaluating the sticker patterns up to a predetermined number N+x and calculating a desired pattern based on at least some of the N to N+x detected sticker patterns. Preferably, N is equal to a number in the range 2 to 10, preferably 2 to 5, particularly preferably equal to 3. Preferably x is equal to a number in the range 2 to 10, preferably 2 to 5, particularly preferred equal to 3. These method steps are preferably carried out in learning mode. When it is detected that the discharged adhesive pattern is a stable pattern and within predefined tolerances for a predefined number of N-1 times, the detected N pattern can be used as the desired pattern. Alternatively, the desired pattern may be calculated using a plurality of at least two adhesive patterns detected within the learning mode, which are stable, that is, their deviations and/or their deviation rates are within a predefined tolerance.

[0035] When the desired new standard has been defined, based on the steps of the previously described method, it is preferred that the tolerance range that was previously changed to the predetermined learning tolerance range is corrected to a predefined tolerance range. This tolerance band is then ideally centered around the calculated desired standard. This predetermined tolerance range may be identical to the tolerance range used before entering learn mode or may be a different tolerance range based on process parameters as previously described. After the tolerance range has been corrected from the predetermined learning tolerance range, the learning mode is preferably abandoned. Subsequently, the method is still carried out in a normal operating mode.

[0036] According to another preferred embodiment of the method, the method comprises the step of: generating a standard failure signal when the detected adhesive pattern is not within the tolerance range of the desired adhesive pattern. The pattern failure signal is generated when the detected sticker pattern is not congruent with the desired sticker pattern.

[0037] In another preferred embodiment, the method comprises the steps of: receiving the pattern failure signal in an alarm device; and generating an alarm signal via the alarm device. Such a device may include an alarm bell, or alarm light, so that an audio alarm or a visual alarm is provided to an operator.

[0038] Furthermore, it is preferred that, alternatively or additionally, the pattern failure signal is received at a disposal device and the disposal device that discards the substrate has the failure sticker pattern. The disposal device may include an arm or thruster or similar mechanical member, which contacts the substrate with the defective pattern to discard the defective substrate. Through these steps, it can be ensured that only substrates with a correct adhesive pattern are supplied at the end of the production procedure.

[0039] The invention achieves its object in a second aspect with an inspection device of the type initially specified, which comprises at least one sensor arrangement having a heat sensor head for detecting a pattern of an adhesive microsphere on the substrate when the even moves along the heat sensor head; an enclosure for housing said heat sensor head, and a controller that is connected to said sensor array, the controller comprising: reference data representing a desired adhesive pattern; and a stored, predetermined tolerance range for the desired adhesive pattern; wherein the controller is adapted to receive signals representing the pattern detected by the sensor arrangement and to compare said signals representing the detected adhesive pattern with the tolerance range of the desired adhesive pattern.

[0040] The controller preferably comprises storage means for the stored and predetermined tolerance range for the desired adhesive pattern and/or the reference data representing the desired adhesive pattern. The storage medium can be formed as a RAM or ROM memory or a flash memory. This embodiment is preferred, in particular, when no other reference value can be obtained, or when the machine is at or shortly after starting. The stored values are preferably based on known typical adhesive patterns, and can be pre-set by the manufacturer and/or operator. Both the reference data representing the desired adhesive pattern and the tolerance range can be changed and adapted by an operator or due to the method described above.

[0041] Preferably, the heat sensor head is housed in a cabinet and the cabinet is adapted for fixing the heat sensor head in close proximity to a nozzle, from which the adhesive is discharged. The enclosure may comprise a mounting section or a mounting device such as clamping means or screws or corresponding screw threaded holes for securing the enclosure to the applicator head, e.g., an applicator body including the nozzle, or other parts of the applicator. applicator, such as the pneumatic solenoid valve housing. The cabinet can also be directly integrated into a main body of an adhesive applicator. The term close proximity in this case refers to the distance between the nozzle opening and the heat sensor head, preferably measured along the direction of movement of the substrate. This distance is preferably in the range of up to 5 cm, preferably in the range of 0.5 cm to 5 cm, more preferably 0.5 cm to 2.5 cm. A smaller distance saves space and leads to better results.

[0042] Furthermore, the inspection device according to the invention comprises a controller, connected to the sensor arrangement. The controller preferably comprises software code for carrying out the method according to the first aspect of the invention.

[0043] The term "pattern" in this case refers to a single microsphere, multiple microsphere portions, and specific arrangements of the microspheres and microsphere portions on a single substrate and includes the position, shape and quantity of adhesive microspheres. . Despite this, "pattern detection" in this case does not necessarily mean that all previously mentioned parameters are detected. It may be sufficient, depending on the embodiment, to detect only one of these parameters or other indicative parameters for a microsphere. Normally, on each substrate, following another, the same adhesive pattern is applied. It should be understood that the term "adhesive" in this case refers to hot-melt adhesive, glue or any other liquid that can be applied heated to join substrates, such as sealants, grease or foamed materials.

[0044] In a first preferred embodiment, the heat sensor is a non-contact sensor. This allows the heat sensor head to be away from the substrate and there is no need to come into contact with the substrate and/or the adhesive pattern. Preferably, the head of the heat sensor is in the range of 5 to 45 mm, preferably 5 to 15 mm, in particular 10 mm in a direction opposite to the substrate, preferably in a direction substantially perpendicular to the surface of the substrate.

[0045] Preferably, the heat sensor head is an infrared sensor. With this infrared sensor, contactless measurement of heat-emitting elements is possible. The substrate is generally at room temperature and the adhesive is applied at elevated temperatures, particularly when a hot-melt adhesive is used. Hot melt adhesive is typically applied at around 100°C to over 200°C and therefore significantly different from ambient temperature. According to the invention, digital as well as analog thermopiles or thermocouples can be used.

[0046] According to another preferred embodiment, the sensor arrangement is disposed in the enclosure which preferably provides thermal insulation to isolate the electronic parts from the heat sensor head and the sensor arrangement from the nozzle head. . This can reduce the mounting space required for the inspection device, and also faster measurements can be performed.

[0047] According to a less alternative preferred embodiment, the heat sensor head is connected to an infrared fiber and the heat sensor head is disposed in a distal position from said nozzle. The heat sensor head in this embodiment may comprise a lens or the like for coupling infrared radiation from the adhesive pattern on the substrate into the infrared fiber. The infrared radiation is then transferred via the infrared fiber to the heat sensor head which can be arranged at a safe distance from the nozzle, so that the heat sensor head is sheltered from the heat radiation from the nozzle, so as not to influence adversely affect the detection of the adhesive pattern on the substrate. According to this embodiment, the cabinet can be maintained with limited dimensions and can be easily connected in close relation to the nozzle, when it houses only the distal free end of the fiber. However, this embodiment requires that the infrared fibers be guided to the sensor, which, in certain embodiments and applications, may not be desired.

[0048] According to a particularly preferred embodiment, the inspection device comprises two or more heat sensor heads that are disposed offset relative to each other in a direction substantially perpendicular to a direction of displacement of said substrate to detect a width and/or center line position in the direction perpendicular to the displacement of said adhesive microsphere on said substrate. This direction is typically called the substrate width direction, perpendicular to the travel direction (machine direction). Preferably, four or more heat sensor heads are arranged offset relative to each other. According to this embodiment, not only the width can be detected, but also the displacement of the microsphere from the desired center line, perpendicular to the machine direction and/or multiple microspheres, arranged parallel to each other on a substrate, can be detected. detected. Additionally, by measuring and/or comparing the signal intensity at each heat sensor head, interpolation can be used to obtain a more accurate estimate of the position and/or width of the microsphere as measured in that heat sensor heads that see only part of the microsphere produce inferior signals than those whose field of view is filled entirely by the microsphere. If heat sensor heads toward the edge of the heat sensor head array detect a stronger signal than those toward its center, the controller may detect that the middle of the microsphere is outside the detection window. The heat sensor heads may be arranged in a row, substantially perpendicular to the machine direction of the substrate, or also offset relative to each other in the direction of travel.

[0049] According to another preferred embodiment, the inspection device comprises two or more heat sensor heads that are arranged offset relative to each other in a direction parallel to the machine direction of said substrate to detect a displacement speed. of said substrate and/or a cooling rate of the adhesive microsphere. The direction will normally be called the length direction of the substrate. When two of the heat sensor heads are arranged offset in the length direction, the displacement speed can be determined when the displacement of the two heat sensors is known, the first heat sensor detects the adhesive microsphere at first and the second heat sensor sees the adhesive microsphere in a second moment, the displacement speed can be calculated by the time difference between these two moments. No encoder to calculate speed based on other parameters is required. Additionally or alternatively, the cooling rate of the adhesive microsphere can be determined in the same way. According to this embodiment, the inspection device can determine the speed of the substrate and/or the cooling rate of the adhesive microsphere itself, without any signal from the external encoder, as well as the position of the pattern relative to the edge of the substrate. This makes integration of the inspection device into existing systems easier without additional programming and cabling efforts. Knowing the displacement speed of the substrate is important because at slower speeds the microsphere becomes wider than at faster speeds when the adhesive discharge volume per time remains constant. Furthermore, the speed of substrate travel determines the delay between the moment the adhesive is applied to a point below the nozzle and the microsphere reaching the sensor, which affects the time between the nozzle discharge signal and the signal. of the sensor being compared, to compare the detected adhesive pattern with a desired adhesive pattern. Additionally, the speed of movement of the substrate also influences the time in which the adhesive cools, if hot-melt adhesive is used, which affects the sensor reading and, therefore, signal quality. Additionally, when the cooling rate of the adhesive microsphere is determined, this value can be used to adjust the sensitivity of the heat sensors. The cooling rate can also form part of verification data and can be used as an indication of bond strength. The temperature of the adhesive plays a strong role in how well the adhesive bonds to the material being bonded.

[0050] In another preferred embodiment, the inspection device comprises at least one mask for a heat sensor head, to restrict a detection area of the heat sensor head. The mask is preferably formed such that a line of sight of the heat sensor head is present only between a specific predetermined width portion of the substrate and the heat sensor head. Due to the mask, it becomes possible to restrict or focus the heat sensor more sharply to the specific detection area, so that it is simple to determine which head of the heat sensor detects which microsphere or portion of the microsphere. It is particularly preferred when two or more, or four or more, or even more heat sensor heads are used. The mask preferably also shelters a portion of the heat sensor head from heat radiation from the nozzle or other parts of the machine, which could negatively influence the operation of the sensor.

[0051] Furthermore, it is preferred that the mask comprises one or more slits, forming sensor openings. The slits can be arranged in a length or width direction, i.e. in a perpendicular or parallel position to a machine direction of the substrate. Preferably, slits that are arranged in a position parallel to the machine direction of the substrate are provided for heat sensor heads used for a width measurement of a microsphere or microsphere portion, and slits perpendicular to the machine direction of the substrate are provided. for heat sensor heads used to determine a length of a microsphere or portion of the microsphere. The slits that form the sensor openings can be designed to be as small as possible so that the measurement tolerance is as small as possible.

[0052] In another preferred embodiment, the cabinet comprises a substantially flat lower portion which, when attached to said applicator head, is directed to said substrate, said lower portion comprising at least one recess, the said at least one heat sensor head is placed within said recess to form said mask. The recess opening is preferably formed as a slit, which forms a sensor opening. These recessed portions formed on a flat bottom portion of the enclosure are a simple way of forming a mask to mask the heat sensors to restrict a sensing area of the heat sensor head.

[0053] According to another preferred embodiment, the controller is connected to a control unit of said nozzle, to receive a discharge signal from said nozzle to determine said desired adhesive pattern. The discharge signal from said nozzle is indicative for the desired adhesive pattern and therefore the desired adhesive pattern can be determined based on the discharge signal from the nozzle. By knowing the distance between the heat sensor head and the nozzle, and the displacement speed of the substrate, the desired moment when a specific heat sensor head should detect an adhesive microsphere or microsphere portion is known. In case the specific heat sensor head detects the microsphere or microsphere portion earlier or later than the determined time point, this is indicative of a defective or poor adhesive pattern and the detected adhesive pattern is not within the tolerances of the desired adhesive pattern and a pattern failure signal can be generated.

[0054] In another preferred embodiment, the inspection device comprises a speed detector for detecting a displacement speed of the substrate, in particular the edge of the substrate. This speed detector preferably comprises an optical detector, such as a photocell. The optical detector is preferably adapted to optically detect a velocity of a substrate. Such an optical detector may comprise two optical sensors that are spaced in a substrate displacement direction by a known predetermined spacing. Through these optical sensors, the speed of the substrate can be easily determined and the distance between the edge and the sticker pattern can be calculated.

[0055] Preferably, the speed detector is mounted in close proximity to the sensor array and/or the heat sensor head. Close proximity in this case means that they are preferably mounted close to each other, preferably within a distance of 0.5 to 5.0 cm, in particular 2.5 cm. Preferably, the speed detector is arranged within the housing to house the heat sensor head.

[0056] Furthermore, it is preferred that the inspection device comprises a mounting bracket for securing the cabinet in a defined relationship to the applicator head. The mounting bracket is preferably formed so that the cabinet has a defined relationship to the nozzle in the direction of travel of the substrate. Preferably, the mounting bracket allows adjustment of the relationship between the cabinet and the nozzle perpendicular to the direction of substrate travel.

[0057] Preferably, the mounting bracket comprises a first engagement section for engaging an applicator head and a second engagement section for engaging the cabinet. The mounting bracket has a known geometry and therefore it is possible to mount the cabinet, which houses at least said heat sensor head, in a known and predetermined relationship with the applicator head and/or the nozzle, at the same time. which allows the adjustment of the distance between the sensor head and the substrate. Preferably, the coupling section and/or the mounting bracket is formed from an insulating material, so that the cabinet, supported by the mounting bracket, is being isolated from the applicator.

[0058] In a preferred development, the first engagement section is adapted to be secured around a nozzle body of the nozzle. For this engagement, the engagement section may comprise first and second arms, which are provided with tightening means, such as a screw and nut, so that the mounting bracket can be secured around a section of the nozzle body, preferably a substantially cylindrical section.

[0059] Alternatively, it is preferred that the first engagement section is adapted to be secured around a portion of a basic body of the applicator head. It can also be adapted to be secured around other predetermined and specific parts or sections of an applicator head, such as connectors, bars, mounting elements, insulating elements such as covers, or the like. It is beneficial when a specific predetermined portion of the applicator head is used to secure the mounting bracket so that the cabinet is supported in a predetermined and defined relationship with respect to the nozzle or nozzle orifice.

[0060] In this case, it is further preferred that the second engagement section of the mounting bracket comprises form-fitting means for engaging the cabinet and the cabinet comprises respective form-fitting means. Such form-fitting means, in particular, may be dovetail-shaped projection and recesses or bow-tie-shaped projection and recesses or other elements that act together in a form-fitting manner.

[0061] Furthermore, said controller is preferably adapted to analyze said detected adhesive pattern for a recurring pattern and to define the recurring pattern as the desired pattern. In another embodiment, said detected adhesive pattern is compared to said pre-stored values of sensor levels to ensure that it is within an acceptable range before configuring it as the desired pattern. When pre-stored values are available in a controller memory store, they are also preferably used to determine whether the detected adhesive pattern is congruent with the desired pattern, i.e., within the defined tolerances of the desired pattern. , which can be determined and/or calculated based on pre-stored values.

[0062] In a third aspect of the invention, the aforementioned object is achieved by an applicator head for dispensing hot-melt adhesive, which comprises a basic body and a nozzle for discharging an adhesive, the applicator head comprising an inspection device according to at least one of the preferred embodiments described above of an inspection device according to the second aspect of the invention, which is preferably fixed to the head of the applicator, in particular the base body, in close proximity to the nozzle . For the preferred embodiments of an applicator head in accordance with the second aspect of the invention, reference is made to the preferred embodiments of the inspection device of the second aspect of the invention, since the applicator head comprises an inspection device. according to the second aspect of the invention.

[0063] The invention will now be described in greater detail with reference to the preferred embodiments and the attached figures, in which:

[0064] Figure 1 shows a side elevation view of an applicator head adapted for use with the present invention;

[0065] Figure 2 shows an elevation view of the applicator head that discharges fluid onto a substrate together with an inspection device of the present invention;

[0066] Figure 3 shows an embodiment of an inspection device of the present invention;

[0067] Figure 4 shows a schematic view of four heat sensor heads together with a mask;

[0068] Figure 5 shows a second embodiment of nine heat sensor heads with a mask;

[0069] Figure 6 shows an inspection device fixed to an applicator head, by means of a mounting bracket according to a first embodiment in an elevated view;

[0070] Figure 7 shows the inspection device fixed to the applicator head by means of the mounting bracket of Fig. 6 in a side view;

[0071] Figure 8 shows an inspection device fixed to an applicator head, by means of a mounting bracket according to a second embodiment in an elevated view;

[0072] Figure 9 shows the inspection device fixed to the applicator head by means of the mounting bracket of Fig. 8 in a side view;

[0073] Figure 10 shows a block diagram illustrating an applicator head with an inspection device;

[0074] Figure 11 shows a signal logic diagram illustrating a method for inspecting an adhesive pattern on a substrate;

[0075] Figure 12 shows a signal logic diagram of a learning mode of the method for inspecting an adhesive pattern on a substrate;

[0076] Figure 13 shows a first diagram showing maximum tolerance curves for the learning mode;

[0077] Figure 14 shows a second diagram showing a learned tolerance curve;

[0078] Figure 15 shows a third diagram that indicates a defined narrow tolerance;

[0079] Figure 16 illustrated a signal output from the device in accordance with the method for inspecting a sticker pattern on a substrate;

[0080] Figures 17a - 17c show schematic views of three substrates with adhesive patterns; It is

[0081] Figures 18a - 18b illustrate a max span measurement.

[0082] Figure 1 shows an applicator head 1 for dispensing a fluid, in particular liquid adhesive material, in particular hot-melt adhesive. Although hot melt adhesive is preferred, other fluids such as glue, sealants, grease or the like can be used. The applicator head 1 includes a base body 4 and a valve 2, preferably a solenoid valve 2, which is mounted on the base body 4. The base body 4 accommodates, among others, internal fluid channels for fluid to be guided through the body. base and a heater to heat the fluid. The applicator head 1 is designed as a pneumatic applicator head with valve 2 which is operated by means of pressurized gas. Valve 2 is preferably a solenoid valve.

[0083] A module 6 provided with a nozzle 8 is fixed to the base body 4. A replaceable filter 10 is provided on an opposite side of the base body 4 from the module 6. A tube connector 12 for supplying the fluid, in particular the hot-melt adhesive, is similarly arranged on the basic body 4. The tube connector 12 is therefore used as a fluid inlet connection and is connected in fluid communication to the module 6 (in a manner not shown) via conduits inside the basic body 4.

[0084] A retention device 14 for fixing the applicator head 1 to a mounting rod or similar elements is also disposed on the basic body 4.

[0085] The solenoid valve 2 of the applicator head 1 has one or more silencers 16, one of which is marked with a reference sign. Solenoid valve 2 is adapted to selectively release and close the pneumatic compressed air line in which compressed air is fed to the applicator head 1 by means of a compressed air head 18. Valve 2 is activated by means of a control signal that can be sent through port 20. The applicator head 1 also has an electrical connector 22 for coupling with a connection cable, which is used to supply electrical energy to the heater located inside the basic body 4.

[0086] According to this embodiment, it is proposed that a controller module is connected to the signal port 20 of the solenoid valve 2 of the applicator head 1. The controller module has a signal input port and a signal output port. signal. For further details regarding this controller module, reference is made to published patent application EP 2,638,978 A1 in the name of Nordson Corporation, Westlake, Ohio. It should be noted that although it is preferred that the controller module is formed in accordance with published patent application EP 2 638 978 A1, this is not necessary. Other modalities without a suture function are also preferred.

[0087] Figure 2 shows an applicator head 1 having a nozzle 8. Although the applicator head 1, according to figure 2, is shown only schematically, it should be understood that the applicator head 1 comprises the essential features of the applicator head 1 shown in Figure 1. The applicator head 1 is connected via its signal port 20 to a signal line 24, connected to a control box 26. The control box comprises a control to the nozzle 8, which sends control signals to the solenoid valve 2 for opening and closing the valve 2 to control the flow of fluid in said nozzle 8. The control unit, provided in the control box 26, may also comprise -as well as means for transforming a primary discharge signal into a secondary discharge signal ("suture"), as described in EP 2 638 978 A1.

[0088] According to Figure 2, an inspection device 30 is provided, preferably in close relation to the nozzle 8 of the module 6 of the applicator head 1 or as a part of the applicator head 1. In this embodiment, The inspection device 30 is fixed to the basic body 4 of the applicator head 1. The device 30 is connected via a signal line 32 to the control box 26. The control box 26 also comprises a controller for controlling the inspection device. inspection 30 (see also Figure 11).

[0089] Both the applicator head 1 and the inspection device 30 are shown in relation to a substrate 34, in the exemplary embodiment illustrated above a substrate 34. The substrate 34, in this case, is a continuous cardboard that is cut into pieces before or after applying the adhesive. The substrate 34 moves in the direction of movement or machine 36 indicated by the arrow. When the substrate 34 moves relative to the applicator head 1, the nozzle 8 discharges adhesive and generates an adhesive pattern 37, which consists of microspheres 38, 39, 40 or other forms (such as dots or films) of adhesive on the surface. top of the substrate 34. The adhesive is, in this case, a hot-melt adhesive that radiates mainly infrared radiation.

[0090] The inspection device 30, according to this embodiment (compare with Figure 2), comprises a cabinet 31 and a sensor arrangement 43 having a heat sensor head 42 (compare with Figure 3) that detects the radiated infrared radiation 44 from the adhesive microsphere 38. According to Figure 2, both the sensor arrangement 43 and the heat sensor head 42 (not shown in Figure 2) are housed in an enclosure 31 of the inspection device 30.

[0091] The controller, provided in the control box 26, receives the signals detected by the heat sensor head 42 via signal line 32 and compares the detected adhesive pattern with a desired adhesive pattern and outputs a failure signal. pattern when the detected sticker pattern 37 is not congruent with the desired sticker pattern. According to the embodiment shown in Figure 2, the controller provided in control box 26 receives information regarding the desired sticker pattern from the control unit, provided in control box 26 as well, which is the discharged signal pattern used to actuate the solenoid valve 2. Since the distance between the heat sensor head 42 and the nozzle 8 in the machine direction 36 is known, it is also known when the heat sensor head 42 should detect or "see" the microspheres 38, 39, 40.

[0092] The control box 26 is further connected to an input signal line 46, which connects the control box 26 to a control device for the entire machine. Furthermore, the control box 26 is connected to a signal line 48 for a pattern failure signal generated by the controller in case the detected sticker pattern 37 is not congruent with the desired sticker pattern. Signal line 48 may be connected to an alarm device, which generates an audio or visual signal in case a pattern failure signal is received (compare with Figure 13).

[0093] Although in the embodiment shown in Figure 2, the sensor arrangement 43 and the heat sensor head 42 are integrated into the housing 31 of the inspection device 30, in the embodiment shown in Figure 3, the heat sensor 43 is disposed distally from the heat sensor head 42. In Figure 3, the enclosure 31 for housing the heat sensor head 42 also houses the sensor arrangement 43, which are not separately shown to simplify the figure. Again an applicator head 1 comprises a solenoid valve 2, a base body 4 and a nozzle 8. Adhesive microspheres 38, 39 are discharged onto a substrate 34 by means of the nozzle 8. According to this embodiment, the sensor arrangement 43 comprises an infrared sensor. The heat sensor head is coupled to an optical fiber 52 comprised of a lens 50 for coupling infrared radiation into an optical fiber 52. The lens 50 is provided in a coupling means 49 that has a screw-threaded portion so that the lens 50 can be fixed to a support. The heat sensor head is disposed in the cabinet 31. Within the cabinet 31 the sensor array 43 is connected to the signal line 48 and the control line 46 to supply the sensor array 43 with electrical power and control signals. Furthermore, the sensor arrangement 43 according to this embodiment is connected via a signal line 53 to the control unit (not shown) of the applicator head 1, to receive control signals for the solenoid valve 2. As may be can be easily seen in Figure 3, the sensor arrangement 43 is positioned at a distance relative to the lens 50, and thus can be arranged at a distance relative to the heated nozzle 8 and the hot-melt microspheres 38, 39, so that the arrangement sensor 43 does not receive excessive heat.

[0094] Figure 4 shows a specific sensor arrangement 43 with four heat sensor heads 42, 52, 54, 56 that are comprised of a mask 60. The mask 60, in this embodiment, is formed as a portion of the housing substantially plane of the cabinet 31 and comprises four recesses 62, 64, 66, 68 in which respective heat sensor heads 42, 52, 54, 56 are disposed. Therefore, the heat sensor heads 42, 52, 54, 56 are recessed behind a surface 61 of the enclosure 31 in the cylindrical recesses 62, 64, 66, 68 which, in Figure 4, extend into the plane of the figure. The openings of the recesses 62, 64, 66, 68 form sensor openings in this case. In this way, the line of sight between the respective heat sensor heads 42, 52, 54, 56 and the adhesive microspheres 38, 39, 40 on the substrate 34 is restricted by means of the recesses 62, 64, 66, 68.

[0095] As can be seen from Figure 4, the heat sensor heads 42, 52 and 54 are disposed substantially parallel to the machine direction 36 of the substrate 34 and the heat sensor head 56 is disposed in a position perpendicular to the machine direction 36 of the substrate 34. The heat sensor head 56 is used to measure the length of a microsphere 38, 39, 40 in the machine direction 36 and the heat sensor heads 42, 52, 54, are used to detecting a width of adhesive application in the machine direction 36. The single heat sensor heads 42, 52, 54, 56 are offset relative to each other in the machine direction 36 and perpendicular to the machine direction. Exemplifying for the heat sensor heads 42 and 52, the displacement O1, O2 is represented in Figure 4. When, for example, the corresponding heat sensor of the heat sensor head 56 indicates that a microsphere is detected and generates a signal, and also the heat sensor corresponding to the heat sensor head 52 generates a signal indicating that an adhesive microsphere is measured, however the heat sensor corresponding to the heat sensor head 42 does not, it is known that the edge of the microsphere parallel to the machine direction 36 is between the heat sensor heads 52 and 42, thereby in the displacement range O1.

[0096] The displacement O2, which is the displacement in the machine direction 36, can be used to determine the displacement speed of the substrate 34. For this purpose, however, it is necessary that both heat sensor heads 42 and 52 see the adhesive microsphere and corresponding heat sensors for heat sensor heads 42 and 52 generate a signal indicating that a microsphere is detected. When, for example, the heat sensor corresponding to the heat sensor head 52 first indicates a signal and then the heat sensor corresponding to the heat sensor head 42 indicates a signal, the time lapse between these two signals can be measured and compared with the spacing between the two heads of the heat sensor, in this way the displacement O2, and subsequently the displacement speed can be measured.

[0097] However, although heat sensors can be used to determine a travel speed, it is further preferred that the inspection device 30 comprises a separate speed detector. In this embodiment, an optical velocity detector, such as two photocells (compare to Figure 11), which are displaced by O2, can be used.

[0098] Figure 5 shows another alternative mask 60 that can be provided for the inspection device 30, described above. In Figure 5, similar and identical parts, already described with reference to Figure 4, are shown with identical reference signs, and so far reference is made to the above description of Figure 4. According to Figure 5, a total of nine heads of heat sensors 42, 52, 54, 56, 70, 72, 74, 76, 78 are provided and each connected to a corresponding heat sensor. Each heat sensor head 42, 52, 54, 56, 70, 72, 74, 76, 78 is provided in a respective recess 62, 64, 66, 68, 80, 82, 84, 86, 88 so that the line of sight between the respective heat sensor head 42, 52, 54, 56, 70, 72, 74, 76, 78 and the substrate 34 is restricted to the focus of the heat sensor head 42, 52, 54, 56 , 70, 72, 74, 76, 78 in a specific area of the substrate 34.

[0099] Again, in accordance with the embodiment of the mask 60 shown in Figure 4, the mask 60 of Figure 5 is formed so that a heat sensor head 56 is disposed in a position substantially perpendicular to the machine direction 36 of the substrate 34 , and the other eight heat sensor heads 42, 52, 54, 70, 72, 74, 76, 78 are arranged substantially parallel to the machine direction 36 of the substrate 34. Due to this arrangement, the size of the heat sensor head heat sensor 56 perpendicular to direction 36 is much longer than the dimension of the heat sensor head 56 in direction 36. Due to this arrangement, the heat sensor head 56 is relatively tolerant with respect to the width of an adhesive microsphere and also to the lateral placement of the microsphere relative to the substrate 34, however using the heat sensor head 56, the length of the microsphere can be detected within relatively small tolerances.

[0100] The other eight heat sensor heads 42, 52, 54, 70, 72, 74, 76, 78 are arranged offset from each other in a position perpendicular to the direction of the machine 36. All these heat sensor heads are arranged with a displacement O1 between them, and are therefore uniformly distributed across the width of the mask 60. Due to this arrangement, detailed detection of the width of the adhesive microsphere and presence in the width direction of the substrate is possible. Additionally, the heat sensor heads are arranged offset relative to each other in direction 36, which is exemplarily shown with respect to heat sensor heads 56 and 42. Due to this displacement O2, the displacement speed of the substrate can be detected.

[0101] Reference is now made to Figures 6 to 9 which each show an applicator head 1 that substantially corresponds to the applicator head 1 shown in Figure 1. So far, reference is made to the above description. Similar elements in Figures 6 to 9 are indicated with identical reference signs. In contrast to the embodiment shown in Figure 1, the applicator head of Figures 6 to 9 comprises a casing 100 that surrounds the basic body 4 and the module 6 (in Figures 6 to 9, now shown).

[0102] The applicator heads 1 of Figures 6 to 9 are provided with an inspection device 30 in accordance with the present invention. The inspection device 30 comprises a cabinet 31 that houses both the heat sensor heads and the heat sensor (in Figures 6 to 9, not shown in detail). Furthermore, a controller 102 is provided which is connected via a signal line 104 to the heat sensors, which are provided in the cabinet 31. According to this embodiment, the controller 102 is provided as a separate unit, whereas in the embodiment shown in Figure 2 and described above, the controller 26 is provided within the control box 26, which is connected to both the cabinet 31 and the applicator head 1. In the embodiment of Figures 6 to 9, the applicator head control box applicator 1 is not shown but could be connected to connector 22. In addition, one of the signal lines 105, 106 is connected to control box 26 (not shown in Figures 6 to 9).

[0103] According to the embodiment shown in Figures 6 to 9, the cabinet 31 is fixed to the applicator head by means of a mounting bracket 110. The mounting bracket 110 comprises a first engagement section 112 for engaging a applicator 1 and a second engagement section 114 for engaging the cabinet 31. Both sections are substantially formed as arms that are perpendicular to each other. The mounting bracket 110 is formed from a heat-insulating material, such as plastic, so that the enclosure 31 is isolated from the nozzle 8. The first engagement section 112, in accordance with the embodiment shown in Figures 6 and 7, is formed to engaging a portion of the nozzle, in particular a circumferential outer surface of the nozzle 8. Therefore, the first engagement section 112 comprises a clamping means 116 for securing the mounting bracket 110 against the nozzle 8. The second engagement section 114 comprises a dovetail-shaped recess 118 and the cabinet 31 comprises a corresponding dovetail-shaped protrusion 120. Due to these corresponding shapes, the cabinet 31 can be fixed against the mounting brackets 110 easily and without additional tools. When engaged, the geometric properties between the enclosure 31 and the nozzle 8 are known over a predetermined range.

[0104] Figures 8 and 9 illustrate an alternative embodiment of the mounting bracket 110. The applicator head elements 1 and the inspection device 30 are substantially identical to those shown in Figures 6 and 7, and heretofore reference is made to the description above and below, in particular, the difference between the two mounting brackets 110 of Figures 6, 7, 8 and 9 is described.

[0105] The mounting bracket 110 again comprises a first engagement section 112 and a second engagement section 114. The first engagement section 112 engages the applicator head and the second engagement section 114 engages the inspection device housing 31 30. In contrast to the embodiment shown above in Figures 6 and 7, the first engagement section 112 is mounted against a portion 122 of the pneumatic solenoid valve 2, in particular, two tubes connecting the base body 4 with the valve 2. Fixing the first engagement section 112 against a portion 122 may be beneficial for applying the hot-melt adhesive, as there is no direct heat bridge from the nozzle 8 to the enclosure 31. Furthermore, it may be beneficial when, for example, the module If nozzle 6 (see Figure 1) needs to be changed, the mounting bracket 110 can still be held in place.

[0106] The first engagement section 112 is substantially U-shaped with two legs 124, 126 extending downwardly from the portion 122 on two opposite sides of the base body 4. In the lowermost portions, the legs 124, 126 are connected to the second engagement section 114. Also, the second engagement section 114 is substantially U-shaped with two legs 128, 130. The legs 128, 130 are connected to the legs 124, 126 via a threaded connection 132.

[0107] Again, as also shown in Figures 6 and 7, the second engagement section 114 comprises a dovetail-shaped recess 118 and the enclosure 31 comprises a corresponding dovetail-shaped projection 120. By means of From the recess 118 and the projection 120, the cabinet 31 can be formally connected to the second engagement section 114. Due to the mounting brackets 110 shown in Figures 8 and 9, the cabinet 31 is in a known and predetermined relationship with the nozzle 8, when engaged.

[0108] Figure 10 shows, in a block diagram, the main arrangement of an inspection device, according to the invention. Again, for identical parts, identical reference signals are used and reference is now made to the above description.

[0109] On the left side of Figure 10, the applicator head 1 is shown as having the valve 2, the base body 4 and the nozzle 8. A discharge signal 200 is intercepted at 202 by the controller 102, before traveling in 204 to the solenoid valve 2. The solenoid valve 2 receives an air supply 206 and provides air flow to the adhesive valve module 4. The adhesive valve module 4 receives a flow of adhesive 208. The nozzle 8 discharges the adhesive 210 onto a substrate 34a, which moves in the machine direction 36. In Figure 10 two further substrates 34b, 34c are shown, onto which an adhesive pattern 37 has already been discharged.

[0110] Controller 102 intercepts discharge signal 200 and determines based on discharge signal 200 the desired adhesive pattern using predetermined tolerances set via tolerance dial 212. The tolerance dial allows an operator to adjust the tolerance desired location within which the discharged sticker pattern should lie. The controller 102 is connected to a sensor array 43, in this embodiment preferably formed as a heat sensor array as shown in Figure 5. The sensor array 43 provides a signal from the heat intensity data matrix 214 to the controller. 102. The inspection device 30 further comprises a speed detector 216 in this embodiment formed as two photocells 218, 219, which detect a leading edge 220 of the substrate 34. The speed detector 216 provides a signal of the presence of substrate and edge speed sensors to the controller 102. The speed detector 216 and the sensor arrangement 43 are disposed in close proximity to each other within the same enclosure (not shown in Figure 10).

[0111] The distance dGSO between the nozzle 8 and the sensing unit, which comprises the speed detector 216 and the sensor arrangement 43, is known. Furthermore, process parameters, in particular delay times, are known. When the discharge signal 200 is generated at t0, it is supplied to the solenoid valve 2. Until the solenoid valve 2 solenoid is energized, it takes time ts. There is additional time for the valve to react, the actual delay for airflow into the sticker valve module. Depending on the type of adhesive used, there is an additional delay time for the adhesive to flow out of the nozzle tip. The delay depends on the type of valve, the pressure and viscosity of the adhesive, and wear on the valve during its life cycle. A high viscosity orifice, low pressure and small nozzle orifice generally lead to a higher ta value. After the adhesive has been discharged, it passes through the air until it comes into contact with the substrate 34. The time tf is the actual delay time for the adhesive to escape from the nozzle tip to the substrate. The parameters ts, tv, ta and tf can be determined experimentally. From the parameters t0, ts, tv, ta, tf, dGSO and the detected velocity vs of the substrate, it is known when the respective heat sensor head should "see" pattern 37, when the discharged pattern 37 is congruent with the desired pattern. If the detected pattern 37 is within the defined tolerance, the sticker pattern 37 is considered congruent. Otherwise, it is detected as a defective pattern and a pattern fault signal 224 is generated by the controller 102.

[0112] Figure 11 illustrates the signal logic of the inspection device 30. The controller 102 intercepts the discharge signal, as described above.

[0113] When the controller determines in the "Signal Active?" step that no discharge signal is received and at the same time the speed detector 216 determines that no substrate is present, it is known that there is no substrate in the detection field of the sensor arrangement 43. The array of detected heat intensity data for this time is therefore a "Background Heat Intensity Value" which is stored and used later when presence of a pattern is determined. When controller 102 determines that a discharge signal is present, it checks whether the pattern has additionally changed in the "Has Pattern Changed?" step. When the pattern has not changed, the normal operating mode is operated. Otherwise, when the pattern has changed, the controller 102 switches to a learning mode 102 (which will be described below with reference to Figure 12). It should be noted that the learn mode is not introduced due to an operator pressing a teach button, but based on changing the pattern itself.

[0114] By means of the tolerance dial 212, four different tolerance values can be set and/or adjusted. First, a "start/end length tolerance" value is defined, then a "width tolerance", a "quantity tolerance", and a "center tolerance" value. The "start/end length tolerance" is used in conjunction with the predetermined speed, which was determined in the "Calculate vs from Edge" step and converted to a time value.

[0115] To detect the adhesive pattern 37, according to this embodiment (Figure 11), the threshold value is used. Looking from the determined background heat intensity value, when a heat above a predetermined threshold value is reached in the "Start of Microsphere Detected?" step, which is determined based on the background heat intensity value, consider It is assumed that an onset of a microsphere is detected until the value decreases below the threshold again. The limit value can be determined experimentally. From the detected substrate speed, the threshold can be adjusted by speed using a known cooling rate factor that is dependent on ambient temperature, substrate speed, adhesive type, and other potential parameters. Furthermore, it is determined when the starting point time is within the estimated total time and within the expected time tolerance in the "Within Expected Time Tolerance?" step, and when it is not within this tolerance, a pattern failure signal is generated.

[0116] When detecting a microsphere start in the "Microsphere Start Detected?" Based on the heat intensity data matrix detected by the heat sensor 43, the "start/end length tolerance" is used to check whether the start time of a microsphere is within the expected tolerance time. This is determined in the “Within Expected Time Tolerance?” step. If it is not ok, a pattern failure signal is generated.

[0117] The width tolerance value can be used in conjunction with a "Width Speed Factor" to determine a speed adjustment width tolerance. If the user selects a speed-dependent width tolerance, which would normally be used when adhesive pressure is not adjusted depending on machine speed and therefore wider microsphere is expected at lower speeds, the width tolerance is placed scaled by speed and stored as a "Width/Speed Factor", which is determined experimentally. Therefore, when the substrate speed is known, it is possible to adjust the width tolerance based on the detected speed. Using the heat intensity data matrix, the left and right edges of the pattern can be detected. From these the width of the pattern can be calculated and it can be checked whether it is within the defined tolerances. The last step is performed in "Width Within Tolerance?". If they are not ok, a pattern failure signal is generated.

[0118] From the calculated width, the length of the microsphere and also a known matrix spacing of the heat sensor matrix, a microsphere area can be calculated. By calculating the area of the microsphere, it can be determined whether the amount of adhesive is within the defined tolerance. This is checked in the "Quantity Within Tolerance?" step. If the determined amount of adhesive on the substrate is not within the defined amount tolerance, a pattern failure signal is released.

[0119] Furthermore, the center of the pattern is determined. Therefore, the "Central Tolerance" value is used. When the left and right edges of the pattern are determined, the center of the microsphere can be calculated. Using the center tolerance value, it is determined whether the microsphere is within this tolerance. This is checked in the "center microsphere?" step. If the center of the microsphere is not within the predetermined tolerance, a pattern failure signal is released.

[0120] With reference to Figure 12, the learning mode is now explained. When the controller 102 detects that a discharge signal has changed (see Figure 11), or that a discharge signal has been detected for the first time, for example after starting the inspection device, the learning mode is entered. In learning mode, status LED 211 is switched to yellow, indicating that controller 102 is in learning mode. When learning mode is entered, the defined tolerance values are overwritten at the highest tolerance level 220, until N cycles have passed. The value N is the learning duration, that is, the number of substrates that are used in the learning mode. For example, ten substrates are used for the learning mode. Depending on the application time, a smaller or larger number can also be used. When in learning mode, the controller tracks the average data matrix values of each of the N patterns. When it is determined that these values are stable, that is, when the absolute change and rate of change between the detected patterns is within predefined tolerances, indicating that there is no increasing/decreasing trend, the average of all or a subgroup of the N detected patterns or a following group of N + x patterns is used to adjust the threshold value, and thus determine a new adjusted desired pattern. After the new desired pattern has been set, the learning mode is terminated and the controller returns to normal operating mode, as shown in Figure 11.

[0121] As stated previously, when in learn mode, tolerances (position, size, amount, center) set by tolerance dial 212 are overridden to a higher stored tolerance level 220, preferably determined through experimentation. to cover a range so that most plausible sensor values are included, both in terms of time (position) and heat/infrared radiation intensity (amount). In terms of time, at one extreme, an application with an adhesive with a low viscosity applied at a high pressure through a small nozzle onto a nearby substrate, which will have rapid valve actuation, flow through the valve and the nozzle rapidly, and a short escape time to the substrate over the short distance, will have a short total delay. At the other extreme, a highly viscous adhesive at low pressure through a large nozzle to a substrate that is further away will have a long total delay. In terms of heat/infrared intensity, at an extreme, a high temperature adhesive applied in large quantities to a moving substrate will quickly reach the sensor with little cooling and produce a high, broad reading from the sensor array. heat. At the other extreme, a low temperature adhesive applied in small quantities at low speeds will produce a low, narrow reading from the matrix. However, the check remains active during learning with these extended tolerances 220 in order to provide a fault output if no or very unusual heat intensity data is received.

[0122] An example of what the threshold intensity level might look like when in learning mode is shown in Figure 13. To be recognized as present, the center of the microsphere preferably results in a reading of at least 100 (compared to with figure 13, "sensor heat intensity value" on the ordinate), and neighboring sensors in the array ideally produce a reading of at least 65. This would correspond to a typical, cold, narrow microsphere. The center of the microsphere (found by looking at the peak on the matrix values curve) can also vary across almost the entire width of the sensor. There could also be higher values particularly for the external sensing elements to ensure that the sensor is still seeing both edges of the microsphere.

[0123] In Figure 13, the abscissa indicates the position of the sensor along the width of the substrate. The ordinate indicates the sensor intensity normalized with an index value. The vertical dashed line 230 indicates an expected center line of a pattern and/or a microsphere. This can be defined by an operator or determined based on pre-stored values. The lower curve 232 shows a lower limit of the tolerance band, and the upper curve 234 indicates the upper limit of the tolerance band. Every curve measured within the area defined between curves 232 and 234 would be within tolerance in learning mode.

[0124] When the controller returns to normal operating mode as shown in Figure 11, the tolerance is corrected to normal mode. This is illustrated in Figure 14. The ordinate indicates the sensor intensity normalized to an index value, and the abscissa indicates the position of the sensor along the width of the substrate, as it was in Figure 13. In the diagram the learned curve 236 of the pattern of desired adhesive is shown. Two threshold curves are extracted, a first threshold level 238 for a fair sensitivity offset and a second, lower one 240 which is adjusted and adapted for slower substrate velocities and/or higher cooling rates, so that the intensity value of sensor heat is lower.

[0125] To facilitate more accurate verification during the learning phase, a custom programming interface can be used to allow the user to enter their application data (microsphere width, set point temperature), which would result in the use of experiment data that matches (or is interpolated to better match) the user conditions to be used to define a narrower learning range for the threshold. This is indicated in Figure 15, which shows a lower curve 242 indicating a lower limit of the defined tolerance range, and an upper curve 244 illustrating an upper limit of the tolerance range. Any detected pattern whose curve would fall between curves 242 and 244 would be considered congruent with the desired adhesive pattern.

[0126] Figure 16 illustrates an output logic of the controller 102. As shown in Figure 10, the controller comprises two status LEDs, 211, 213. The status LED 211 in accordance with this embodiment can switch between green and yellow and the status LED 213 can switch between white, blue and green. While the status LED 211 is used to indicate whether the controller 102 is in learning mode (yellow) or working mode (green), the status LED 213 is used to indicate whether the last product is defective or not. As described above with reference to Fig. 11, it checks whether the detected microsphere is within the length tolerance, width tolerance, quantity tolerance and center tolerance. Therefore, checking a microsphere start/end position relative to the edge of the substrate, checking the microsphere width, checking the microsphere position perpendicular to the substrate path, and checking the amount of adhesive (microsphere area) are carried out. If any of these tolerances are not met, a failure counter is incremented. At the same time, the status LED 213 is switched to blue. Otherwise, when all tolerances are met, the status LED 213 remains green. At the same time, it can be provided that the status LED 213 also flashes white when a weak pattern is detected. Alternatively, at the end of the pattern cycle, the status LED 213 may be switched white with a high voltage signal if the number in the fault counter has reached a predetermined threshold.

[0127] Figures 17a to 17c show different examples of adhesive patterns 37a, 37b, 37c. Reference is first made to Figure 17a. In Figure 17a a row of three substrates 34a, 34b, 34c is shown, with the machine direction being to the left with respect to Figure 6a. On the substrate 34a, an adhesive pattern 37a is discharged including an adhesive microsphere 38a and an adhesive microsphere 39a. Between these two microspheres 38a, 39a, a gap 90 is provided. On the subsequent substrate 34b, again, an adhesive microsphere 38b and an adhesive microsphere 39b are discharged. Between the two microspheres 39a and 39b, a gap 91 is provided. There is a gap 92 between the adhesive microspheres 38b and 39b, which is identical in length to the gap 90. Consequently, a gap 93 is provided between the microspheres 39b and 38c , which are discharged onto the third substrate 34c. The gap 93 is identical in length to the gap 91. When the substrate 34a moves along the inspection device 31 (see Figures 2, 11), firstly the microsphere 38a is detected by means of the heat sensor head. After gap 90, the adhesive microsphere 39a is then detected and after gap 91 the adhesive microsphere 38b is detected. In case the controller, provided in the control box 26 of the heat sensor 43, receives the discharge signal from the applicator head control unit 1, the detection of the adhesive pattern 37a and also in comparison with the detected adhesive pattern 37a with the desired sticker pattern can be started directly based on the discharge signal.

[0128] In a learning mode, the controller analyzes the detected sticker pattern 37a for a recurring pattern and sets the recurring pattern to the desired pattern. The controller acts in this case as follows: After the microsphere 39a has been detected, it is compared with the microsphere 38a and the controller analyzes that the microsphere 39a is not identical to the microsphere 38a. After detection of the microsphere 39a, the gap 91 is detected and then again the microsphere 38b is detected. After detecting the microsphere 38b, the controller analyzes that the microsphere 38b is congruent with the microsphere 38a. After microsphere 38b, gap 92 is detected and the controller analyzes that gap 92 is congruent with gap 90. The controller now expects that after this gap 92, a microsphere would follow that which would be substantially identical to microsphere 39a. After the detection of microsphere 39b, this assumption can be verified. Microsphere 39b is again followed by gap 93 which is congruent with gap 91 and therefore a recurring pattern has been identified. Upon detection of the gap 93, thus starting from the microsphere 38c, the controller sets the detected adhesive pattern 37a as the desired adhesive pattern and thus, starting from the substrate 34c, automatic detection and comparison of the pattern of detected adhesive with the desired adhesive pattern, which is the recurring pattern in this case, can be started. It may be provided that before a detected recurring pattern is defined as the desired pattern, one or more repetitions of the pattern must be detected. It may, for example, be provided that a repetition of a detected recurring pattern is necessary. In this case, the automatic comparison between the detected pattern and the desired adhesive pattern can be started after the substrate 34c, thus with a substrate 34d, which follows the substrate 34c (which, however, is not shown in Figure 17a).

[0129] In Figures 17b and 17c, different alternative adhesive patterns 37b, 37c are shown. Considering these two standards 37b, 37c, the same as explained above regarding standard 37a is applicable. Pattern 37b consists of three adhesive microspheres 38a, 39a, 40a that are spaced apart by gaps, which are not shown with reference signs in Figures 17b and 17c. Although the adhesive pattern 37b, 37c shown in Figs. 17b and 17c is more complex than the sticker pattern 37a of Figure 17a, the same detection and analysis method as the sticker pattern 37b, 37c can be applied here.

[0130] In Figures 18a and 18b, schematically, two adhesive patterns are shown comprising adhesive microspheres 38, 39, 40, 41. While Figure 18a illustrates a high tolerance for a maximum gap G1, Figure 18b shows a low tolerance for maximum span G2. During application of the high tolerance as shown in Figure 18A, the distance between the trailing edge 338 of the first microsphere 38 and the trailing edge 340 of the third microsphere 40 is measured. Thus, a pattern is within tolerances in case the microsphere 39 is missing, and also the front portion of the microsphere 40 is missing. As long as trailing edges 338 and 340 are detected, this pattern will be determined to be within the G1 tolerance.

[0131] In contrast to this, Figure 18b illustrates a low tolerance for the maximum gap G2. At this low tolerance, the trailing edge 338 of the first microsphere 38 and the trailing edge 339 of the second microsphere 39 are compared. When the second microsphere 39 is completely absent, this pattern will not be considered to be congruent with the desired adhesive pattern. However, it is still possible that the leading portion of the microsphere 39 is missing, and the pattern as shown in Figure 18b will be considered to be within tolerance when the trailing edges 338 and 339 are correctly detected.

Claims (32)

1. Method for inspecting a sticker pattern (37) that is on a substrate (34), the method being characterized by the fact that it comprises: providing, to a controller (102), reference data representing a sticker pattern (37) desired; providing the controller (102) with a stored and predetermined tolerance range for the desired adhesive pattern (37); receiving, via the controller (102), a discharge signal (200) from a nozzle control unit (8) to discharge the adhesive; determining, via the controller (102), the desired pattern based on the received discharge signal; detecting, by means of the controller (102), whether a change in the discharge signal (200) occurs or whether the discharge signal (200) is detected for the first time; if the controller (102) detects a change in the discharge signal (200), or the discharge signal (200) is detected for the first time, setting the tolerance band to the desired standard for a predetermined learning range; discharging an adhesive microsphere (38, 39, 40, 41) onto a substrate (34) from the nozzle (8); detecting a pattern of the adhesive microsphere (38, 39, 40, 41) discharged onto the substrate (34), when the substrate (34) moves, by means of a sensor arrangement (43); receiving, via the controller (102), signals representing the pattern detected by the sensor arrangement (43); and comparing, by means of the controller (102), said signals representing the detected adhesive pattern (37) with the tolerance range of the desired adhesive pattern (37). 2. Method according to claim 1, characterized by the fact that it further comprises: calculating the predetermined tolerance range of the desired adhesive pattern (37) using pre-stored values. 3. Method according to claim 1, characterized by the fact that it further comprises: calculating the predetermined tolerance range using pre-detected values. 4. Method according to claim 1, characterized by the fact that detecting the pattern of the discharged adhesive microsphere (38, 39, 40, 41) comprises: determining, by means of the controller (102), an intensity or rate of change in intensity of a value detected by the sensor arrangement (43); comparing, by means of the controller (102), the intensity or rate of change in intensity with a limit value stored in the controller (102); and determining, via the controller (102), that a microsphere edge (338, 339, 340) is present when the intensity or rate of change in intensity exceeds the threshold value stored in the controller (102). 5. Method according to claim 4, characterized by the fact that it further comprises changing the limit value scale based on a substrate speed (34) or a cooling rate factor. 6. Method according to claim 1, characterized by the fact that it further comprises: determining, by means of the controller (102), a displacement speed and edge position (220) of said substrate using a speed sensor of the sensor arrangement (43) by means of: determining an intensity or rate of change in the intensity of a value detected by the speed sensor; comparing the intensity or rate of change in intensity with a pre-stored threshold in the controller (102); and determining whether an edge (220) of the substrate is present when the intensity or rate of change in intensity exceeds the threshold. 7. Method according to claim 1, characterized by the fact that determining the desired adhesive pattern (37) comprises calculating a desired microsphere start time (38, 39, 40, 41) and a microsphere end time (38, 39, 40, 41) using at least one predetermined delay value pre-stored in the controller (102). 8. Method according to claim 7, characterized by the fact that the predetermined delay value comprises: a valve delay time (2) that defines a delay between a discharge signal (200) and a moment when the adhesive starts flowing out of the nozzle (8); an adhesive flight time that defines a time between the exit of the adhesive from the nozzle (8) and contact with the substrate (34); or a substrate travel time (34) that defines a time that the substrate (34) needs to move from the nozzle (8) to the sensor arrangement (43). 9. Method according to claim 1, characterized by the fact that detecting the pattern of the adhesive microsphere (38, 39, 40, 41) comprises detecting a width of the microsphere (38, 39, 40, 41). 10. Method, according to claim 6, characterized by the fact that the tolerance band comprises a width tolerance dependent on the displacement speed of the substrate (34). 11. Method according to claim 1, characterized by the fact that it further comprises: providing a centerline tolerance range to the desired adhesive pattern (37); calculating a center line of the detected sticker pattern (37); and compare the calculated centerline with the centerline tolerance band. 12. Method, according to claim 1, characterized by the fact that it additionally comprises calculating an area of the substrate (34) that is covered by the microsphere (38, 39, 40, 41). 13. Method according to claim 12, characterized by the fact that it further comprises: providing a value of a desired area covered by the microsphere (38, 39, 40, 41); provide a quantity tolerance for the area covered by the microsphere (38, 39, 40, 41); and comparing the calculated area covered by the microsphere (38, 39, 40, 41) with the quantity tolerance. 14. Method according to claim 13, characterized by the fact that it further comprises: providing a tolerance for a thermal intensity value of the desired area; measuring or calculating a thermal intensity value of the calculated area of the substrate (34) that is covered by the microsphere (38, 39, 40, 41); and compare the thermal intensity value of the calculated area with the tolerance for the thermal intensity value. 15. Method according to claim 1, characterized by the fact that it further comprises: providing a tolerance for a maximum gap (G1, G2) between two microspheres (38, 39, 40, 41) of the desired adhesive pattern (37) ; calculating a gap (90, 91, 92, 93) between the two microspheres (38, 39, 40, 41) of the detected pattern (37); and compare the calculated span (90, 91, 92, 93) with the tolerance for a maximum span (G1, G2). 16. Method according to claim 1, characterized by the fact that it further comprises emitting a pattern failure signal (224) when the detected sticker pattern (37) does not fall within the tolerance range of the sticker pattern (37) desired. 17. Method according to claim 16, characterized by the fact that it further comprises: receiving the pattern failure signal (224) in an alarm device; and generating an alarm signal using the alarm device. 18. Method according to claim 16, characterized by the fact that it further comprises: receiving the pattern failure signal (224) in a disposal device; and discarding the substrate (34) that has a defective adhesive pattern. 19. Method according to claim 1, characterized by the fact that the sensor arrangement (43) can be attached to an applicator head (1) in close proximity to the nozzle (8). 20. Method, characterized by the fact that it comprises: storing a predetermined tolerance range for a desired adhesive pattern (37) in a controller (102); receiving a discharge signal (200) from a control unit of a nozzle (8) for discharging the adhesive into the controller (102); determining, by means of the controller (102), the desired adhesive pattern (37) based on the discharge signal (200) received; receiving a change in discharge signal (200); detecting whether a change in the discharge signal (200) occurs or whether the discharge signal (200) is detected for the first time; and if the controller (102) detects a change in the discharge signal (200), or the discharge signal (200) is detected for the first time, set the tolerance band to the desired pattern (37) for a tolerance band predetermined learning process. 21. Method according to claim 20, characterized by the fact that said learning range is based on pre-stored values that correspond to predetermined adhesive patterns. 22. Method, according to claim 20, characterized by the fact that it additionally comprises: discharging an adhesive microsphere (38, 39, 40, 41) onto a substrate (34) from the nozzle (8); detecting a pattern of the adhesive microsphere (38, 39, 40, 41) on the substrate (34) using a sensor array (43); comparing a detected sticker pattern (37) with at least one previously detected sticker pattern (37); and determining whether a detected deviation or rate of deviation from the standard since the change in discharge signal (200) was detected is within a predefined tolerance. 23. Method according to claim 22, characterized by the fact that it comprises: achieving a predetermined number of N-1 detected sticker patterns (37), once the change in the discharge signal (200) or the discharge signal (200) has been received by the controller (102); using the detected pattern N as the desired adhesive pattern (37); and evaluating the sticker patterns (37) up to a predetermined number N+x and calculating, via the controller (102), a desired sticker pattern (37) based on the detected sticker patterns N to N+x. 24. Method according to claim 20, characterized by the fact that it further comprises a return of the learning tolerance range to the predetermined tolerance range. 25. Method, according to claim 24, characterized by the fact that it further comprises centering the predetermined tolerance band around the desired adhesive pattern (37). 26. Inspection device (30) for inspecting an adhesive pattern (37) on a substrate (34), the inspection device (30) being characterized by the fact that it comprises: at least one sensor arrangement (43) having a heat sensor head (42, 52, 54, 56, 70, 72, 74, 76, 78) for detecting a pattern of an adhesive microsphere (38, 39, 40, 41) on the substrate (34) when the substrate (34) moves relative to the heat sensor head (42, 52, 54, 56, 70, 72, 74, 76, 78); a controller (102) in electrical communication with said sensor arrangement (43), the controller (102) storing: reference data representing a desired adhesive pattern (37); and a predetermined tolerance range for the desired adhesive pattern (37); wherein the controller (102) is configured to: receive a discharge signal (200) from a control unit of a nozzle (8) to discharge the adhesive; determining the desired adhesive pattern (37) based on the discharge signal (200) received; receiving signals representing the pattern detected by the sensor array (43); and detecting whether a change in the discharge signal (200) occurs or whether the discharge signal (200) is detected for the first time; If the controller (102) detects a change in the discharge signal (200), or the discharge signal (200) is detected for the first time, set the tolerance band for the desired adhesive pattern (37) for a range of predetermined learning; and comparing said signals representing the detected adhesive pattern (37) with the tolerance range of the desired adhesive pattern (37). 27. Inspection device (30), according to claim 26, characterized by the fact that the heat sensor comprises two or more heat sensor heads (56) that are arranged offset in a direction substantially perpendicular to a direction of displacement of said substrate (34) to detect a width or center line position in the direction perpendicular to the displacement of said adhesive microsphere (38, 39, 40, 41) on said substrate (34). 28. Inspection device (30), according to claim 26, characterized by the fact that the heat sensor comprises two or more heat sensor heads (42, 52, 54, 70, 72, 74, 76, 78) which are arranged offset in a direction substantially parallel to a machine direction (36) of said substrate (34) to detect a displacement speed of said substrate (34). 29. Inspection device (30), according to claim 26, characterized by the fact that the heat sensor comprises two or more heat sensor heads (42, 52, 54, 70, 72, 74, 76, 78) which are arranged offset in a direction substantially parallel to a machine direction (36) of said substrate (34) to detect a cooling rate of the adhesive microsphere (38, 39, 40, 41). 30. Inspection device (30), according to claim 26, characterized by the fact that it additionally comprises a mask (60) for the heat sensor head (42, 52, 54, 56, 70, 72, 74, 76 , 78) to restrict a detection area of the heat sensor head (42, 52, 54, 56, 70, 72, 74, 76, 78). 31. Inspection device (30), according to claim 26, characterized by the fact that it further comprises a speed detector (216) for detecting an edge (220) of the substrate or a speed of the substrate. 32. Method according to claim 1, characterized by the fact that detecting the discharged adhesive microsphere (38, 39, 40, 41) comprises: determining an intensity or rate of change in the intensity of a characteristic detected by the sensor arrangement (43 ); determining that the intensity or rate of change in intensity exceeds a threshold; and determining, based on determining that the intensity or rate of change in intensity exceeds the threshold, that a microsphere edge (338, 339, 340) is present.