Method for checking adhesion between layers of building board and corresponding device

Abstract

The invention relates to a device (40) for checking the adhesion between two layers of material of a building board (9) formed by cutting a stream of layers of material stacked and adhered together on a production line in order to produce a building board provided with an edge surface, the invention relates to an inspection device (40) for a building panel (9), comprising means for detecting an adhesion defect between two layers of material, characterized in that the detection means comprise at least:-means (13) for capturing an image of an edge surface of the building panel (9), and-means (7) for analyzing the image thus captured.

Description

Technical Field

[0001] The present invention relates to the construction industry, and more particularly to the manufacture of building panels based on gypsum or another material such as cement. The present invention more specifically relates to:

[0002] - A method for checking the adhesion between a layer of material such as gypsum and an outer layer of material holding the layer of material, these different layers constituting such a building panel,

[0003] - Associated inspection equipment and

[0004] - A method for manufacturing such a panel. Background Art

[0005] In particular, gypsum-based building panels are manufactured on a production line by spreading an inner layer of gypsum mixed with water on an outer layer of paper or fiberglass material, and then covering the inner layer with another outer layer of paper or fiberglass material. These inner and outer layers are then dried and cut into building panels. The outer layer adheres to the inner layer by winding gypsum crystals around the paper or fiberglass of the outer layer, and the hydration of the material promotes this winding, which allows the formation of pores between the crystals. Poor adhesion between these layers results in the detachment of the outer layer, which is particularly harmful when dealing with dried panels or packaged panels.

[0006] Currently, in order to check the adhesion quality between the inner gypsum layer and the outer paper layer on a building panel, the operator makes a cross on the surface of the panel sampled on the production line and tries to detach the paper from the surface, or tries to detach the paper directly from the edge of the panel. If the operator can remove all the paper without leaving paper with insufficient thickness adhering to the gypsum, the adhesion between the inner gypsum layer and the paper layer on the building panel is not satisfactory. Otherwise, the adhesion quality is considered satisfactory. Thus, these manual inspections are time-consuming and may not be repeated identically because the detachment force and speed particularly depend on the operator.

[0007] Furthermore, this type of inspection is typically carried out on wet building panels before the panels are dried, i.e., before the adhesion between the gypsum and the paper crystals is fully formed. One of the reasons is to avoid blocking the dryer when the paper detaches during the drying of the panels. These prior art inspections are carried out randomly on several building panels at different points on the production line, and the frequency of these inspections is a function of the variability of the materials used and the stability of the manufacturing process on this production line. Therefore, the adhesion between the materials of the different panels being inspected is not in the same formation stage during these inspections. The time taken by the operator to inspect the panel affects the adhesion quality, which is manually evaluated by others. Similar inspections are also carried out during the manufacture of gypsum panels covered with fiberglass.

[0008] Therefore, these prior art inspections do not allow quantification of the quality of the adhesion between the different materials of the building panels, let alone the same reliable quantification for all building panels on the production line. Summary of the Invention

[0009] The object of the present invention is to at least partially remedy the drawbacks of the prior art by providing a method for inspecting the adhesion between the layers of a building panel, a related device, and a method for manufacturing a building panel incorporating such an inspection method, which allows quantification of the quality of the adhesion between the layers of the building panel with higher reliability.

[0010] To this end, the present invention proposes a method for inspecting the adhesion between at least two material layers of a building panel, which is formed by cutting a stream of material layers stacked and adhered together on a production line in order to manufacture a building panel provided with edge surfaces. The inspection method includes a step of detecting adhesion defects between the two material layers, and is characterized in that the detection step includes sub-steps:

[0011] - Capturing an image of the edge surface of the building panel, and

[0012] - Analyzing the image thus captured.

[0013] Thanks to the present invention, the good adhesion between the gypsum or cement layer in the building panel and the outer layer of the building panel made of paper or fiberglass material is inspected in the same way on the panels in the production line, without manually tearing the outer layer of the building panel. Image capture is used to detect the natural detachment of the material layers due to insufficient formation of the adhesion between these material layers. Preferably, for all building panels inspected, the detection step is carried out at the same point in the production line. Even more preferably, each panel of the production line is inspected by the inspection method according to the present invention.

[0014] It should be noted that the building panel may include material layers other than gypsum and paper or fiberglass-based materials, and the present invention is applicable to any type of building panel whose manufacture may cause detachment problems between the material layers. For example, the building material includes a cement inner layer covered with a paper or fiberglass outer layer.

[0015] According to an advantageous feature of the method for inspecting adhesion according to the present invention, the sub-step of capturing the image is preceded by a sub-step of sending a gas onto the edge surface of the building panel. The gas is, for example, air or water vapor. Sending water vapor can prevent the panel from overheating during subsequent drying steps.

[0016] When the material layers do not have a strong enough adhesion to prevent such detachment, this sub-step of sending gas promotes the detachment of the material layers and thus allows quantification of the quality of the adhesion. It should be noted that this detachment naturally occurs between layers of different materials, rather than between two sub-thicknesses of paper as may occur when manually tearing paper on a building panel as in the prior art.

[0017] According to another advantageous feature of the method for checking adhesion according to the present invention, during the sub-step of sending gas, the gas is sent at a predetermined pressure between 1 bar and 6 bar. This relative pressure (i.e., added to atmospheric pressure) remains, for example, at the same value throughout the detection step or is modulated according to the position of the building panel before it reaches the camera for the image capture sub-step. For example, the pressure varies according to a pressure ramp. A position sensor for the building panel on the production line can preferably be used to interrupt the sending of the pressurized gas between two detection steps.

[0018] According to another advantageous feature of the method for checking adhesion according to the present invention, the analysis sub-step provides a value representative of the detachment level between two material layers on at least a portion of the edge surface, and is followed by a sub-step of comparing the value representative of the detachment level with a predetermined detachment threshold. This representative value is, for example, a measure of the maximum detachment between the two material layers visible on the captured image or the average detachment between the two layers calculated after analyzing the captured image.

[0019] Preferably, when the building panel includes more than two material layers and thus includes at least two interfaces between the layers, the analysis sub-step provides a value representative of the detachment level of each interface between two layers of the material layers of the building panel or of the two interfaces between the material layers, and each representative value is compared with the detachment threshold predetermined in the comparison sub-step.

[0020] More preferably, the comparison sub-step is followed by a diagnostic sub-step which, once at least one representative value provided by the analysis sub-step is greater than the detachment threshold, concludes that there is an adhesion fault, or if this is not the case, the diagnostic sub-step concludes that there is no adhesion fault. This diagnosis is displayed on a screen and allows, for example, the operator to eject the panel from the production line and / or quickly adjust the parameters of the production line in case of a fault.

[0021] The present invention also relates to a manufacturing method for manufacturing a building panel including at least two material layers on a production line, the manufacturing method comprising the following steps:

[0022] - Stacking the material layers to produce a stream of stacked material layers;

[0023] - Forming an adhesion between the thus stacked material layers, and

[0024] - Cutting a stream of material layers stacked and bonded together to form building panels,

[0025] The manufacturing method is characterized in that it implements the inspection method according to the present invention.

[0026] In one embodiment of the present invention, the layers of the stacked material are gypsum layers and paper layers.

[0027] The forming step starts earlier than the stacking step because the gypsum mixed with water and deposited on the paper layer may start to bond to the paper. This forming step using the hydration of the material may include adding additives during the premixing step of the gypsum and water. The cutting step may be carried out during this bonding formation step.

[0028] Preferably, the step of forming the bond is followed by a step of drying the material layer, and the detection step occurs between the cutting step and the drying step. In this way, defective panels can be detected before moving to the drying step.

[0029] According to an advantageous feature of the method for manufacturing building panels according to the present invention, the detection step is followed by a step of ejecting the building panel from the production line when at least one value representative of the detachment level provided by the analysis sub-step is greater than an upper threshold value. This high threshold corresponds, for example, to the dimensions of the inlet of the dryer used during the drying step. In this way, when the detachment is too large, the building panel is not directly fed into the dryer where there is a risk of clogging.

[0030] According to another advantageous feature of the method for manufacturing building panels according to the present invention, the detection step is followed by a step of adjusting at least one parameter of the production line based on at least one value representative of the detachment level provided by the analysis sub-step or based on the conclusion of the diagnostic sub-step. For example, when the material layer includes a gypsum layer and a paper layer, before the step of stacking the material layers, during the step of mixing these amounts to form the gypsum layer, this parameter is the amount of water used per unit amount of dry gypsum. The water / dry gypsum ratio is adjusted to promote the formation of the bond between the gypsum layer and the paper layer. If it is diagnosed that there is no bonding failure, then, for example, the amount of water used per unit amount of dry gypsum is reduced during this adjustment step. The amount of water per unit amount of dry gypsum adjusted here relates to the entire gypsum layer or only to one or more interfacial sub-layers of this gypsum layer, at the interface between the gypsum layer and one or more material layers outside this gypsum layer. In this case, the mixing step may include different mixtures, such as an initial mixture of water, wet gypsum, and any other compounds, which is configured to form the main inner layer of the gypsum, and then this initial mixture is modified to manufacture the interfacial sub-layer. The term "mixture" is used here in a broad sense and can be understood as "preparation of the mixture".

[0031] According to an advantageous feature of the method for manufacturing building panels according to the present invention, the layers of the stacked material include a gypsum layer, and the manufacturing method includes a plurality of inspection steps performed on different building panels continuously arriving at a point on a production line, and an analysis sub-step of providing a value representing a zero detachment level for each interface between two layers of the stacked material, followed by an adjustment step that includes reducing the amount of water used per unit amount of dry gypsum to form a mixture before the step of the layers of the stacked material, the mixture being configured to form a gypsum layer or an interface sub-layer between the gypsum layer and another stacked material layer, and repeating the adjustment step after each subsequent analysis sub-step until the subsequent analysis sub-step provides a value representing a non-zero detachment level but less than a predetermined detachment threshold. Thus, at the interface between the gypsum layer and one or more layers of material outside the gypsum layer, this reduction in water affects the entire gypsum layer or only one or more interface sub-layers of the gypsum layer.

[0032] In one embodiment of the invention, the stacked material layers include a gypsum layer, and the at least one parameter is selected from the list comprising:

[0033] - On the one hand, the ratio between the amount of an accelerator for the chemical reaction between water and the gypsum of the gypsum layer and on the other hand the amount of a retarder for the chemical reaction between water and the gypsum of the gypsum layer, the amounts of the accelerator and the retarder being injected into the mixture configured to form the gypsum layer during a mixing step before the stacking step,

[0034] - A certain amount of a foaming agent injected into the mixture,

[0035] - A certain amount of a fluidizing agent injected into the mixture,

[0036] - The amount of water used per unit amount of dry gypsum for forming the mixture,

[0037] - The target density of the gypsum layer of the building panel, and

[0038] - The target weight of the building panel.

[0039] During this adjustment step, several parameters can be adjusted simultaneously. The above list is of course non-exhaustive. For example, the target density is adjusted by changing the amount of foaming agent injected during the mixing step or the amount of water used per amount of dry gypsum during the mixing step, which affects the entire gypsum layer or only one or more interface sub-layers of the gypsum layer at the interface between the gypsum layer and one or more layers of material outside the gypsum layer.

[0040] For example, the layers of the stacked material include at least one gypsum layer and a layer stacked on the gypsum layer, the gypsum layer includes a sub-layer bordering the layer stacked on the gypsum layer, and the at least one parameter is selected from the list comprising:

[0041] - On the one hand, the ratio between the amount of accelerator for the chemical reaction between water and the gypsum in the interfacial sublayer and, on the other hand, the amount of retarder for the chemical reaction between water and the gypsum in the interfacial sublayer, the amounts of accelerator and retarder are injected into the mixture configured to form the interfacial sublayer before the stacking step,

[0042] - A certain amount of foaming agent injected into the mixture,

[0043] - The amount of water used per unit amount of dry gypsum for forming the mixture,

[0044] - The target density of the interfacial sublayer of the building board, and

[0045] - The target weight of the interfacial sublayer.

[0046] In one embodiment of the present invention, the method for manufacturing a building board according to the present invention includes a plurality of inspection steps performed on different building boards continuously arriving at a point on a production line, and after each inspection step is a step of adjusting at least one of the parameters, the adjustment step using an adjuster that receives as input the difference between the current setpoint value of the at least one parameter on the production line and the estimated value of the at least one parameter based on at least one value representative of the deviation level from the inspection step. In other words, in this embodiment of the present invention, the adjustment step is performed according to an adjustment loop. Of course, this uses a model to estimate the value of the parameter corresponding to a given deviation level. When a plurality of parameters are changed during these adjustment steps, the model includes as many variables as there are parameters.

[0047] Finally, the present invention relates to a device for inspecting the adhesion between two material layers of a building board, the building board being formed by cutting, stacking, and bonding together a stream of material layers on a production line so as to manufacture a building board provided with edge surfaces, the inspection device including means for detecting adhesion defects between the two material layers, and being characterized in that the detection means at least includes:

[0048] - Means for capturing an image of the edge surface of the building board, and

[0049] - Means for analyzing the image thus captured.

[0050] Advantageously, the inspection device further includes at least one nozzle for sending gas to the edge surface of the building board at a predetermined pressure.

[0051] Advantageously, the inspection device includes means for detecting the position of the building board on the production line, and means for sending gas according to the position detected by the detection means. These gas sending means are, for example, one or more of the nozzles described above.

[0052] Finally, in the inspection device according to the present invention, the main direction of the gas jet through the nozzle is preferably oriented to face the edge surface of the building board and / or parallel to the longitudinal movement direction of the building board. Description of the Drawings

[0053] The inspection device according to the present invention includes advantages similar to those of the inspection method and the manufacturing method according to the present invention.

[0054] On the one hand, other features and advantages of the present invention will become apparent from the following description, and on the other hand, from a plurality of examples of embodiments given by way of illustration and not limitation with reference to the accompanying schematic drawings, wherein:

[0055] Figure 1 shows the steps in the method for manufacturing a building board according to the present invention in an embodiment of the present invention,

[0056] Figure 2 shows the production line of the building board according to the present invention in this embodiment of the present invention,

[0057] Figure 3 represents the device for inspecting the adhesion between two material layers of a building board according to the present invention before the detection step implemented by this inspection device in this embodiment of the present invention,

[0058] Figure 4 represents during the detection step implemented by this inspection device in this embodiment of the present invention Figure 3 the inspection device,

[0059] Figure 5 represents during the detection step implemented by this inspection device in this embodiment of the present invention, by Figure 3 and Figure 4 the images taken by the inspection device,

[0060] Figure 6 represents an embodiment of the step for adjusting the parameters of the manufacturing method according to the present invention in the context of the embodiment of the present invention, and

[0061] Figure 7 represents another embodiment of the step for adjusting the parameters of the manufacturing method according to the present invention in another context of the embodiment of the present invention. Detailed Embodiments

[0062] According to an embodiment of the present invention, in combination with Figure 1 and Figure 2 ​​​​​​​A manufacturing method 1 for manufacturing building boards according to the present invention is described. More specifically, in this embodiment of the present invention, the manufacturing method 1 allows for the manufacture of gypsum boards covered with paper layers and is implemented by the Figure 2 production line 3 shown. These building boards are thin rectangular boards that include a gypsum inner layer 901 (as Figure 5 shown) and paper outer layers 900, 902 on the surfaces of these boards. Each paper outer layer 900, 902 actually includes papers of multiple thicknesses, for example, papers of two or three thicknesses.

[0063] Return to reference Figure 1 and Figure 2 , the first step in the manufacturing method according to the present invention is the firing 80 of gypsum, which forms gypsum. After this first step is step 90, in which the thus obtained gypsum is mixed with water and any other compounds detailed below. This mixing step 90 produces a wet gypsum mixture. Some of this mixture can be used to change its properties, for example, using specific additives, and is configured to form a gypsum sublayer, as described below.

[0064] The next step in the manufacturing method according to the present invention is the stacking 100 of material layers 900, 901, 902 on the production line 3. For this purpose, the wet gypsum mixture obtained in the mixing step 90 is spread on the first layer of paper 900, the edges of the paper are folded to accommodate the mixture, and then it is covered with the second layer of paper 902. As these materials advance on the production line 3, they are integrally compressed by an extruder formed by a pair of rollers, thereby allowing the thickness of the stacked layers to be corrected.

[0065] In the case where the mixing step 90 includes sampling of the mixture, this mixture sampling is configured to form an interface sublayer in the gypsum layer 901 with a composition or density different from the rest of the gypsum layer 901 in the paper layers 900, 902. The production line 3 includes one or more specific rollers. These specific rollers are used to spread a sample of the mixture having a composition or density different from the rest of the mixture onto the paper layers 900, 902, thereby forming a wet gypsum interface sublayer on each paper layer 900, 902. Then, in the stacking step 100, the rest of the mixture is spread onto the first layer of paper 900 covered with one of the previously formed interface sublayers. The rest of the mixture thus spread forms the inner part of the gypsum layer 901. Then this inner part is covered with the second layer of paper 902, and the other of the previously formed interface sublayers is arranged between the inner part and the second layer of paper 902.

[0066] In this stacking step 100, the first layer 900 of paper, the layer 901 of gypsum, and the second layer 902 of paper are stacked in the following order, and this stacking of layers is continuous throughout the manufacturing method 1. Thus, at the output of step 100, the layers 900, 901, 902 of the stacked materials result in a flow of long material layers 900, 901, and 902.

[0067] The deposition of the wet gypsum mixture between the paper layers 900 and 902 contributes to the formation of an adhesive portion between the paper layers 900, 902 and the gypsum layer 901. Thus, the stacking step 100 is part of the step 200 of forming an adhesive portion between the material layers 900, 901, 902. This step 200 of promoting the formation of the adhesive portion is achieved by hydrating the gypsum layer and the paper layers with water from the mixing step 90. At the interface between the gypsum layer 901 and the paper layers 900, 902, this hydration promotes the formation of gypsum crystals, and when the gypsum crystals harden, the gypsum crystals surround the fibers of the first layer of paper in the paper layers 900, 902, thereby allowing the formation of an adhesive portion between the paper layers 900, 902 and the gypsum layer 901. This adhesive portion ensures good adhesion between the paper layers 900, 902 and the gypsum layer 901. During the mixing step 90 before the stacking step 100, an additive or an accelerator can be added to the water in the gypsum mixture to respectively promote or accelerate the formation of this adhesive portion. Thus, this step 200 of forming the adhesive portion includes forming gypsum crystals that wind around the paper fibers, and this formation is completed before the building panel 9 enters the drying step 500, during which hot air is blown onto the building panel 9. This drying step 500 allows the removal of the excess water added during the mixing step 90 to improve the fluidity of the wet gypsum mixture.

[0068] After the stacking step 100 is the cutting step 300 of cutting the flow of the material layers 900, 901, 902 into rectangular building panels 9 (as Figure 3 and Figure 4 shown), and the rectangular building panels 9 move along the production line on the rotating rollers 8. By way of illustration, these building panels 9 are approximately 2.5 meters long.

[0069] In this embodiment of the present invention, the cutting step 300 occurs after the stacking step 100, when the gypsum is hard enough, and before the drying step 500.

[0070] According to the present invention, the manufacturing method 1 further includes a step 400 of detecting adhesive defects between the material layers 900, 901, 902 (such as between the gypsum layer 901 and the first paper layer 900 and / or between the gypsum layer 901 and the second paper layer 902). This detection is performed on the edge surface of the building panel 9, that is, after the cutting step 300.

[0071] In this embodiment of the invention, the detection step 400 occurs between the cutting step 300 and the drying step 500, i.e., during the bonding portion forming step 200. This is actually a "wet" detection. This "wet" detection step 400 is advantageously carried out as close as possible to the cutting device used during the cutting step 300, so that on the one hand there is a weaker adhesion and thus it is easier to characterize between the gypsum layer 901 and the paper layers 900, 902, and on the other hand it allows for the rapid ejection of defective sheets, as well as the rapid activation of a feedback loop that allows adjustment of the manufacturing method 1 according to the invention when a defect is detected, as described below.

[0072] In an alternative embodiment of the invention, the detection step 400 is carried out after the drying step 500, in which case it is a "dry" detection. Of course, these two detections can be combined.

[0073] This detection step 400 is preferably carried out on all building sheets 9 moving on the production line 3 during the implementation of the manufacturing method 1 according to the invention. Alternatively, the detection step 400 is carried out only on a sample of the building sheets 9, for example only on one building sheet 9 out of ten building sheets running on the production line 3.

[0074] The detection step 400 is the main step in the method 4 for checking the bonding between two material layers in the building sheet 9, which is implemented in hardware and software by the Figure 2 and Figure 3 inspection device 40 shown in.

[0075] The inspection device 40 includes at least one camera 13 attached to a beam and docked with a computer 7 via a wireless link 14 (such as a Wi-Fi connection using the IEEE 802.11 standard). Preferably, a plurality of cameras are used to monitor the entire edge surface of the building sheet 9. Preferably, the inspection device 40 further includes an illumination system that can illuminate the edge surface of the sheet 9 such that the detachment of the paper layer 900 or 902 from the gypsum layer 901 forms a shadow between the paper layer 900 or 902 and the gypsum layer 901, thus facilitating the contour detection performed during the image analysis sub-step described later.

[0076] The inspection device 40 further includes at least one nozzle 11 for sending a gas (in this case pressurized air 12) to the building sheet 9 arriving on the production line 3. On this production line 3, due to the rollers 8, the building sheets move in the longitudinal direction L in the moving direction 10. The building sheet 9 is cut in its width direction along a transverse direction T orthogonal to the longitudinal direction L and the vertical direction V during the cutting step 300.

[0077] One or more nozzles 11 are preferably arranged between the rollers 8 of the same section of the production line 3 in the transverse direction T, and are preferably arranged such that their air jets have a direction substantially parallel to the longitudinal direction, i.e., parallel to the longitudinal direction L within a few degrees (e.g., within 10 degrees). In this way, their air jets are substantially orthogonally directed towards the edge surfaces of the building panels 9 manufactured in the cutting step 300. The nozzles 11 are arranged vertically below the camera 13 and longitudinally near the longitudinal position of the camera 13.

[0078] In this embodiment of the invention, it is preferred to use a single nozzle 11 placed vertically below the vertical position of the building panel 9, the air jet of which forms an angle, for example, between 5° and 15° with the longitudinal direction L. This allows testing the adhesion between the gypsum layer 901 and the first paper layer 900 and the adhesion between the gypsum layer 901 and the second paper layer 902. For reasons of cost and simplicity, this main embodiment is preferred because only one nozzle is used and there is no need to adjust the nozzle position 11 according to the thickness of the building panel 9. However, alternative embodiments are possible, where the angle is, for example, between 5° and 20°, between 5° and 30°, or between 5° and 45°. Alternatively, the nozzle 11 can be used only to test the adhesion between the gypsum layer 901 and a single layer of paper 900 or 902.

[0079] In another embodiment, a nozzle 11 is used which is placed vertically above the vertical direction of the building panel 9, and the air jet from this nozzle forms an angle between 5° and 15°, between 5° and 20°, between 5° and 30°, or between 5° and 45° with the longitudinal direction L. The vertical position of the nozzle 11 is adjusted according to the thickness of the building panel 9. In this alternative embodiment, the nozzle 11 tests the adhesion between the gypsum layer 901 and each of the paper layers 900, 902, or between the gypsum layer 901 and a single paper layer 900, 902. Finally, combinations of these variants can be envisaged, where two nozzles are used, one placed vertically below the vertical position of the building panel 9 and the other placed vertically above the vertical position of the building panel 9.

[0080] In Figure 3 for example, the building panel 9 is wetted and has just passed through the cutting step 300, and the air 12 sent through the nozzle 11 reaches below the surface of the building panel 9. On the other hand, in Figure 4 the nozzle 11 blows the air 12 towards the edge surface of the building panel 9 moving in the travel direction 10. This air 12 is preferably sent at a pressure slightly above atmospheric pressure (e.g., two bar). This relative air pressure 12 (i.e., added to the atmospheric pressure) at the outlet of the nozzle 11 is predetermined and is between 1 bar and 6 bar.

[0081] The air 12 leaving the nozzle 11 is sent continuously at the same pressure, for example as it passes through the building panel 9.

[0082] Alternatively, when the inspection method is configured to associate a pressure threshold with the detachment of one of the paper layers 900, 902 from the gypsum layer 901, the pressure of the air 12 at the outlet of the nozzle 11 varies according to a rising pressure ramp. This pressure threshold allows quantification of the adhesion level between the paper layer 900 or 902 and the gypsum layer 901. This configuration is activated by the operator, for example. The inspection device includes a man-machine interface, in particular a screen, which allows observation of the detachment of one of the paper layers 900 or 902 from the gypsum layer 901 using the camera 13. This screen can also be used to display the measurement results and diagnostic results generated by the detection step 400, as described below. These measured values and diagnostic values are displayed for each building panel 9 inspected by the inspection method according to the invention. Preferably, one diagnostic value and one measured value are displayed for the adhesion between the first paper layer 900 and the gypsum layer 901, and another diagnostic value and another measured value are displayed for the adhesion between the second paper layer 902 and the gypsum layer 901.

[0083] It is also preferred that the nozzle 11 sends the air 12 only when the edge surface of the building panel 9 faces the nozzle 11. For this purpose, a position sensor for the panel 9 on the production line 3 interacts with the nozzle 11 by means of the computer 7.

[0084] Return to Figure 1 The detection step 400 includes a first sub-step of sending 410 the air 12 through the nozzle 11 onto the edge surface of the building panel 9 facing the nozzle 11.

[0085] The next sub-step is to capture 420 an image of the edge surface of the building panel 9 by the camera 13. When the adhesion between the paper layer 900 and the gypsum 901 or between the paper layer 902 and the gypsum 901 is insufficient to allow good adhesion of the paper to the gypsum, the air 12 blown onto the edge surface of the building panel 9 allows one of the paper layers 900 or 902 to detach from the gypsum layer 901.

[0086] Therefore, the capture sub-step 420 provides Figure 5 the image 130 shown in, where the detachment 921 between the gypsum layer 901 and the paper layer 902 potentially indicates poor adhesion between the paper layer 902 and the gypsum layer 901. The image 130 is displayed on the screen of the inspection device 40. In this example of using the inspection method according to the invention, it can be seen that the paper layer 900 has not detached from the gypsum layer 901, indicating good adhesion between these two layers 900 and 901.

[0087] The next sub-step is the analysis 430 of the image 130 obtained during the previous capture sub-step 420. This image analysis uses contour detection to identify the different layers of the building board 9, as well as the detachment 921 between the paper layer 902 and the gypsum layer 901. In this analysis sub-step 430, this contour detection is followed by the measurement of the maximum detachment visible on the image 130 between the layers 901 and 902 of the materials of the building board 9. This measurement represents the detachment level between the material layers 901 and 902 of the building board 9. In this analysis sub-step 430, further contour measurements between the material layers 900 and 901 give a zero value for the maximum detachment between these material layers 900 and 901.

[0088] Given that in this example of an embodiment of the present invention, only the second paper layer 902 is detached from the gypsum layer 901, the steps and sub-steps of these methods related to this detachment 921 will only be described in detail in the following description of the inspection method and the manufacturing method. These steps and sub-steps can be converted to the case where the gypsum layer 901 and the first paper layer 900 are also detached from each other, or the case where both the first paper layer 900 and the second paper layer 902 are detached from the gypsum layer 901.

[0089] In an alternative embodiment of the present invention, this analysis sub-step 430 provides an average value of the detachment between the paper layer 902 and the gypsum layer 901 on at least a part of the edge surface of the building board 9. This average value also represents the detachment level between the material layers 901 and 902 of the building board 9. In another embodiment, the analysis sub-step 430 provides a value of the detachment area between the material layers 901 and 902 of the building board 9, and this area value can also be considered as a value representing the detachment level between the material layers 901 and 902 of the building board 9.

[0090] The next sub-step is the comparison 440 between the measured value Dmes of the maximum detachment and a predetermined detachment threshold S1. This specified detachment threshold S1 is set, for example, to 2 mm (millimeters). Preferably, this predetermined detachment threshold S1 is between 1 mm and 4 mm. Alternatively, the detachment threshold S1 is, for example, 1 mm, 3 mm or 4 mm.

[0091] In an alternative embodiment of the present invention using the average value of the detachment between the paper layer 902 and the gypsum layer 901, the comparison sub-step 440 compares this average value with a predetermined detachment threshold S1 set, for example, to 1 mm.

[0092] The next sub-step is the diagnosis 450, which determines whether there is an adhesion defect or no adhesion defect between the material layers whose detachment is measured in the analysis sub-step 430. In this diagnosis sub-step 450, if at step 440, the value representing the maximum detachment level (thus the measured value Dmes of the maximum detachment or the average detachment value in the corresponding embodiment) is greater than the predetermined detachment threshold S1 (Figure 1 at the output of step 440 in branch Y), the diagnostic sub-step 450 determines that there is an adhesion failure between the gypsum layer 901 and the paper layer 902, otherwise ( Figure 1 at the output of step 440 in branch N), the diagnostic sub-step 450 determines that there is no adhesion failure between the gypsum layer 901 and the paper layer 902. In the latter case, the next step is the drying step 500. The diagnosis generated by the diagnostic sub-step 450 is displayed on the screen of the inspection device according to the invention.

[0093] In this embodiment of the invention, when the diagnostic sub-step 450 determines that there is an adhesion defect between the gypsum layer 901 and the paper layer 902, after the detection step 400 is the step 550, which compares the value representing the maximum detachment level with an upper threshold S2, where the upper threshold S2 corresponds to the maximum detachment value acceptable for the building panel 9 to pass through the dryer. This high threshold S2 can be equal to the predetermined detachment threshold S1 (in which case step 550 is not necessary and after the diagnostic sub-step 450 is the step 600 of ejecting the building panel 9 from the production line 3 as soon as an adhesion failure is detected), but preferably is strictly greater than the predetermined detachment threshold S1. In this embodiment of the invention, this high threshold S2 is set to 6 mm. Alternatively, it can be set at 3 mm, 4 mm or 5 mm, while always remaining higher than the predetermined detachment threshold S1, and in these variants, the detachment threshold is, for example, 1 mm, 3 mm or 4 mm respectively.

[0094] If the step 550 of comparing the value representing the maximum detachment level with the upper threshold S2 determines that the representative value is greater than the upper threshold S2, then (branch N at the output of step 550) the next step is the step 600 of ejecting the building panel 9 from the production line 3. In this way, the defective building panel 9 does not pass through the drying step 500 and there is a risk of blockage due to the narrowness of the dryer nozzle used during this drying step 500.

[0095] On the other hand, if the step 550 of comparing the value representing the maximum detachment level with the upper threshold S2 determines that the representative value is less than the upper threshold S2, then (branch Y at the output of step 550) the next step is the drying step 500.

[0096] In addition, in this embodiment of the present invention, after the detection step 400, there may be a step 700 of adjusting the parameters of the production line 3. This adjustment step is conditional on the value representing the detachment level obtained during the analysis sub-step 430 or at the end of the diagnosis sub-step 450. For example, once an adhesion failure is diagnosed in the diagnosis sub-step 450, the adjustment step 700 is enabled. In particular, in order to keep the value representing the detachment level below a predetermined threshold S1, or below another threshold lower than this predetermined threshold S1, which then corresponds to the target detachment threshold, one or more of the following parameters are changed during this adjustment step 700, which are listed here in order of priority:

[0097] - An amount of accelerator added during the mixing step 90 for forming gypsum crystals in the gypsum layer 901. This accelerator accelerates the formation of hydrated calcium sulfate from the calcium sulfate hemihydrate and water present in the gypsum during the mixing step 90. The accelerator is, for example, a heat-resistant accelerator (HRA), such as small gypsum crystals;

[0098] - An amount of retarder for forming gypsum crystals in the gypsum layer 901 added during the mixing step 90. Such a retarder, well-known to those skilled in the art, allows delaying the formation of hydrated calcium sulfate during the mixing step 90, and on the one hand is used to prevent the formation of lumps in the mixing device used during this mixing step 90, which would require stopping the production line, and on the other hand makes the mixture obtained from this step less viscous so that it cannot be spread on the layer of paper 900;

[0099] - The amount of foaming agent injected during the mixing step 90, which forms stable or unstable foam; as this amount increases, the adhesion between the paper and the gypsum potentially decreases. Preferably, a foaming agent that produces unstable foam or a mixture of unstable and stable foam is used;

[0100] - The target density of the gypsum layer 901 of the building panel 9. The greater the density, the better the adhesion between the paper layer 900 or 902 and the gypsum layer 901. For example, the density of the gypsum layer is increased or decreased by increasing or correspondingly decreasing the amount of water used per unit amount of dry gypsum during the mixing step 90. However, increasing this amount of water means increasing the energy used during the drying step 500 of the building panel. Therefore, preferably, instead of the density of the gypsum layer, it is the density of the gypsum sublayer at the interface between the gypsum layer 901 and the paper layers 900 and 902, as mentioned above in connection with the mixing 90 step and the stacking 100 step, which is changed by varying the amount of water per unit amount of dry gypsum in these gypsum sublayers. Another way to change the density of the gypsum layer 901 of the building panel 9 is to inject more or less air into the gypsum layer using a foaming agent as described above. Preferably, when the latter solution is chosen, only the density of the gypsum sublayer at the interface between the gypsum layer 901 and the paper layers 900 and 902 is changed, which means that the overall density of the building panel 9 is not significantly changed;

[0101] - The amount of water used per unit amount of dry gypsum during the mixing step 90; in fact, below the critical value of this water / dry gypsum ratio, the adhesion between the paper layer 900 or 902 and the gypsum layer 901 is not satisfactory. On the other hand, too high a water / dry gypsum ratio deteriorates the strength of the paper and thus reduces the interface between the paper layer 900 or 902 and the gypsum layer 901. Preferably, only when the production line 3 includes the above-mentioned specific rollers, this amount of water is used as a parameter in the adjustment step 700 in order to change only the amount of water used in the mixture portion sampled during the mixing step 90 and to form a gypsum sublayer at the interface between the gypsum layer 901 and the paper layers 900 and 902;

[0102] - Injecting a certain amount of an additive during the mixing step 90, which promotes the adhesion between the paper layer 900 or 902 and the gypsum layer 901. This amount of additive can relate only to the interface sublayer between the gypsum layer 901 and the paper layers 900, 902;

[0103] - The duration of the bonding portion forming step 200, which can be changed by adjusting the speed of the production line 3;

[0104] - The target weight of the building panel 9, in particular achieved by changing the flow rate of the air injected into the gypsum mixture during the mixing step 90; the greater the amount of air injected, the worse the adhesion between the paper layer 900 or 902 and the gypsum layer 901. Preferably, only when the production line 3 includes the above-mentioned specific rollers, this target weight is used as a parameter during the adjustment step 700 in order to change only the amount of air injected into the gypsum sublayer at the interface between the gypsum layer 901 and the paper layers 900 and 902;

[0105] - A certain amount of a fluidizing agent is injected into the mixture. The liquefying agent is an additive that can be added to the mixture formed in mixing step 90 to make the mixture more fluid and thus easier to spread over paper layers 900, 902 without adding more water to the wet gypsum mixture.

[0106] It should be noted that the mixture of gypsum and water produced in step 90 also advantageously includes starch, which is an additive that promotes adhesion between paper layer 900 or 902 and gypsum layer 901, but only during drying. During drying step 500, the starch contained in the mixture migrates to the interface between the gypsum layer and the paper layer and gels. In embodiments where the detection step 400 occurs after the drying step 500, the amount of starch in the mixture at step 90 can thus be adjusted in this step 700.

[0107] Furthermore, since the correct balance between the amounts of accelerator and retarder improves the adhesion of gypsum layer 901 to paper layers 900, 902 without adversely affecting the fluidity of the wet gypsum mixture prepared in step 90, the parameters of the amounts of accelerator and retarder can alternatively be replaced by a parameter that is the ratio between the amounts of accelerator and retarder used in mixing step 90.

[0108] In this embodiment of the invention, when the value representative of the detachment level obtained during analysis sub-step 430 is greater than a predetermined detachment threshold S1 or a target detachment threshold, a plurality of adjustment steps 700 are implemented after a plurality of detection steps are continuously performed on different building boards 9. These adjustment steps 700 are repeated until the value representative of the detachment level obtained during the last analysis sub-step 430 becomes less than or equal to the predetermined detachment threshold S1 or the target detachment threshold. These adjustment steps 700 use Figure 6 the regulator 15 shown in to change the setpoint value Pcons of one of the above parameters used to improve the adhesion between layers of materials 901 and 902, such as the amount of water per unit amount of dry mortar during mixing step 90. The regulator is, for example, of the proportional, integral, derivative type (also known as PID). This amount of water per unit amount of dry gypsum corresponds to the amount of water used to form gypsum layer 901 or a gypsum sub-layer at the interface between gypsum layer 901 and paper layers 900, 902.

[0109] During adjustment step 700, the PID regulator receives as input the difference between the current setpoint value Pcons of the parameter on production line 3 and the estimated value Pest of the parameter, where the estimated value Pest is based on the value representative of the detachment level from detection step 400 prior to adjustment step 700. This estimation Pest of the value of the parameter (here the amount of water per amount of dry gypsum) uses model 16, which gives the amount of water per amount of dry gypsum used during mixing step 90 as a function of the value representative of the detachment level. The model is, for example, determined empirically.

[0110] In this embodiment of the present invention, when the value representative of the detachment level obtained during analysis sub-step 430 is zero, i.e., the layers of materials 901 and 902 do not detach from each other on the edge surface of the sheet 9 inspected during inspection step 400, one or more adjustment steps 700 are performed to reduce the amount of water per unit amount of dry gypsum used during mixing step 90.

[0111] In this case, as Figure 7 shown, the adjustment step 700 is repeated until the value representative of the detachment level obtained in the last analysis sub-step 430 becomes non-zero but less than or equal to a predetermined detachment threshold S1 or a target detachment threshold.

[0112] More precisely, after the analysis sub-step 430 of manufacturing method 1, in the first comparison sub-step 441, it is checked whether the value representative of the detachment level obtained in the analysis sub-step 430 is zero.

[0113] If this is the case ( Figure 7 branch Y in), then the amount of water per unit amount of dry mortar used in mixing step 90 is reduced, and the first comparison sub-step 441 is repeated in the subsequent analysis sub-step 430.

[0114] On the other hand, if the value representative of the detachment level obtained during analysis sub-step 430 is non-zero ( Figure 7 branch N in), then the second comparison sub-step 442 checks whether the value representative of the detachment level obtained during analysis sub-step 430 is less than or equal to a predetermined detachment threshold S1 or a target threshold. If this is the case ( Figure 7 branch Y in), then the adjustment step 700 is not repeated, at least until the subsequent inspection step 400 diagnoses an adhesion failure between the material layers 900, 901 and 902, or provides a value representative of zero-level detachment. If this is not the case ( Figure 7 branch N in), then the adjustment circuit in Figure 6 is used to increase the amount of water per unit amount of dry gypsum used in mixing step 90.

[0115] Of course, the present invention is not limited to the examples just described, and many adjustments can be made to these examples without departing from the scope of the present invention.

Claims

1. A method (4) for checking the adhesion between at least two material layers (900, 901, 902) of a building panel (9), the building panel (9) being formed by cutting a stream of material layers (900, 901, 902) on a production line so as to manufacture a building panel provided with edge surfaces, the material layers (900, 901, 902) being stacked and adhered together, the checking method (4) comprising a step (400) of detecting an adhesion defect between the two material layers (900, 901, 902), characterized in that the detecting step (400) comprises the following sub-steps: - capturing (420) an image (130) of the edge surface of the building panel (9), and - analyzing (430) the thus-captured image (130).

2. The method (4) for checking adhesion according to claim 1, characterized in that, Before the sub-step of capturing (420) the image (130) is a sub-step of sending (410) a gas (12) onto the edge surface of the building panel (9).

3. The method (4) for checking adhesion according to claim 2, characterized in that, During the sub-step (410) of sending the gas (12), the gas (12) is sent at a predetermined pressure between 1 bar and 6 bar.

4. A method (4) for checking adhesion according to any one of the preceding claims, characterized in that, The analyzing sub-step (430) provides a value representative of a detachment level (Dmes) between the two material layers (900, 901, 902) on at least a portion of the edge surface, followed by a comparison sub-step (440) of comparing the value representative of the detachment level (Dmes) with a predetermined detachment threshold (S1).

5. The method for checking (4) bonding according to claim 4, wherein, The building panel (9) comprises more than two material layers (900, 901, 902), and wherein the analyzing sub-step (430) provides a value representative of a detachment level (Dmes) for each interface between two of the material layers (900, 901, 902) of the material layers of the building panel (9), each representative value being compared with the detachment threshold (S1) predetermined in the comparison sub-step (440).

6. The method (4) for checking adhesion according to claim 4 or 5, characterized in that, After the comparison sub-step (440) is a diagnostic sub-step (450), which determines that there is an adhesion failure once at least one representative value (Dmes) provided by the analyzing sub-step (430) is greater than the detachment threshold (S1), or determines that there is no adhesion failure if this is not the case.

7. A manufacturing method (1) for manufacturing a building panel (9) on a production line, the building panel (9) comprising at least two material layers (900, 901, 902), the manufacturing method (1) comprising the following steps: - stacking (100) the material layers (900, 901, 902) to produce a stream of stacked material layers; - forming an adhesion portion (200) between the thus-stacked material layers (900, 901, 902), and - cutting (300) the stream of stacked and adhered-together material layers to form a building panel (9), characterized in that the manufacturing method (1) implements the checking method (4) according to any one of claims 1 to 6.

8. A method for manufacturing (1) a building panel (9) according to claim 7, wherein, The step of forming the bonding portion (200) is followed by a step of drying (500) the material layers (900, 901, 902), and the detecting step (400) occurs between the cutting step (300) and the drying step (500).

9. The method for manufacturing (1) building panels (9) according to claim 7 or 8, wherein, The stacked material layers (900, 901, 902) are a gypsum layer and a paper layer.

10. The method (1) for manufacturing a building panel (9) according to any one of claims 7 to 9 in combination with claim 4 or 5, wherein, When at least one value representative of the detachment level (Dmes) provided by the analysis sub-step (430) is greater than the upper threshold (S2), the detecting step (400) is followed by a step of ejecting the building panel (9) from the production line (600).

11. A method for manufacturing (1) building panels (9) according to any one of claims 7 to 10 in combination with claim 4, 5 or 6, wherein, The detecting step (400) is followed by a step of adjusting (700) at least one parameter of the production line based on at least one value representative of the detachment level (Dmes) provided by the analysis sub-step (430) or based on the conclusion of the diagnostic sub-step (450).

12. The method for manufacturing (1) building boards (9) according to claim 11, wherein, The stacked material layers (900, 901, 902) include a gypsum layer (901), and wherein the at least one parameter is selected from the list comprising the following:[[]] - On the one hand, the ratio between the amount of an accelerator for the chemical reaction between water and the gypsum of the gypsum layer (901) and on the other hand, the amount of a retarder for the chemical reaction between water and the gypsum of the gypsum layer (901), during the mixing step (90) before the stacking step (100), injecting the amounts of the accelerator and the retarder into the mixture configured to form the gypsum layer (901), - A certain amount of a foaming agent injected into the mixture, - A certain amount of a fluidizing agent injected into the mixture, - The amount of water used per unit amount of dry gypsum for forming the mixture, - The target density of the gypsum layer (901) of the building panel (9), and - The target weight of the building panel (9).

13. The method for manufacturing (1) a building panel (9) according to claim 11, wherein, The stacked material layers (900, 901, 902) include at least one gypsum layer (901) and layers (900, 902) stacked on the gypsum layer (901), the gypsum layer (901) includes a sub-layer at the interface with the layers (900, 902) stacked on the gypsum layer (901), and wherein the at least one parameter is selected from the list comprising the following:[[]] - On the one hand, the ratio between the amount of an accelerator for the chemical reaction between water and the gypsum of the interface sub-layer and on the other hand, the amount of a retarder for the chemical reaction between water and the gypsum of the interface sub-layer, before the stacking step (100), injecting the amounts of the accelerator and the retarder into the mixture configured to form the interface sub-layer, - A certain amount of a foaming agent injected into the mixture, - The amount of water used per unit amount of dry gypsum for forming the mixture, - The target density of the interface sub-layer of the building panel (9), and - The target weight of the interface sub-layer.

14. The method for manufacturing (1) building panels (9) according to claim 11, which depends on claim 5, wherein, The stacked material layers (900, 901, 902) include a gypsum layer (901), the manufacturing method (1) includes a plurality of inspection steps (400) performed on different building boards (9) continuously arriving at a point on a production line, and wherein the analysis sub-step (430) provides values representing a zero detachment level (Dmes) for each interface between two stacked material layers (900, 901, 902), followed by an adjustment step (700), the adjustment step (700) including: before the step of stacking (100) the material layers, reducing the amount of water used per unit amount of dry gypsum to form a mixture configured to form the gypsum layer (901) or an interface sub-layer between the gypsum layer (901) and another stacked material layer (900, 902), repeating the adjustment step (700) after each subsequent analysis sub-step (430) until the subsequent analysis sub-step (430) provides a value representing a non-zero detachment level (Dmes) but less than the predetermined detachment threshold (S1).

15. An apparatus (40) for checking the adhesion between two material layers (901, 902) of a building panel (9), said building panel (9) being formed by cutting a stream of material layers (900, 901, 902) on a production line so as to manufacture a building panel provided with edge surfaces, said material layers (900, 901, 902) being stacked and adhered together, said checking apparatus (40) comprising means for detecting adhesion defects between said two material layers (901, 902), and characterized in that, The inspection device at least includes: - a device (13) for capturing an image (130) of the edge surface of the building board (9), and - a device (7) for analyzing the image (130) thus captured.

16. The device (40) for checking adhesion according to claim 15, characterized in that, The device (40) further includes at least one nozzle (11) for sending a gas (12) to the edge surface of the building board (9) at a predetermined pressure.

17. The device (40) for checking adhesion according to claim 16, including a device for detecting the position of the building board (9) on a production line, and a device for sending the gas (12) according to the position detected by the inspection device.

18. An inspection device (40) for inspecting the adhesion along the direction 15 or 16, wherein, The main direction of jetting the gas (12) through the nozzle (11) is oriented to face the edge surface of the building board (9) and / or parallel to the longitudinal movement direction of the building board (9).

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