Method for inspecting adhesion between layers of construction panels and corresponding device

Abstract

The present invention relates to an apparatus (40) for inspecting the joints between at least two layers (900, 901, 902) of material in a construction panel (9) formed by cutting on a production line a flow of layers (900, 901, 902) of material that have been stacked and joined together to produce an edge-faced construction panel, characterized in that the inspection apparatus (40) comprises means for detecting a joint failure between two of said layers (901, 902), said detection means comprising at least means (13) for capturing an image (130) of the edge surface of said construction panel (9) and means (7) for analyzing said image (130) thus captured.

Description

[Technical Field]

[0001] The present invention relates to the construction industry, and in particular to the manufacture of construction panels based on plaster or other materials such as cement. The present invention more particularly relates to a method for inspecting a joint between a layer of material, such as gypsum, and an outer layer of material that grips this layer of material, these different layers making up such a construction panel; Associated inspection equipment; a method for manufacturing such a panel; Regarding. [Background technology]

[0002] In particular, gypsum-based construction panels are manufactured on a production line by spreading an inner layer of gypsum mixed with water onto 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 multiple construction panels. The outer layer adheres to the inner layer by entanglement of gypsum crystals around the paper or fiberglass of the outer layer. This entanglement is facilitated by hydration of the materials, which can lead to the formation of crystals and voids between these crystals. Lack of adhesion between these layers can result in delamination of the outer layer, which is particularly disadvantageous when the panel is dried or packaged.

[0003] Currently, to inspect the quality of the bond between the inner layer of gypsum and the outer layer of paper in a construction panel, an operator creates a cross on the surface of a sampled panel on the production line and attempts to peel the paper from this surface, or peels the paper directly from the edge of the panel. If the operator can peel all of the paper without leaving a thickness of paper stuck to the gypsum, the bond between the inner layer of gypsum and the outer layer of paper in the construction panel is insufficient. Otherwise, the quality of the bond is deemed sufficient. Such manual inspections are time-consuming and not reproducible, especially since peeling force and speed vary depending on the operator.

[0004] Furthermore, this type of inspection is often performed on wet construction panels before they dry, i.e., before the bonds between the gypsum and paper crystals have fully formed. One reason for this is to avoid clogging the dryer with peeling paper as the panels dry. Such prior art inspections are performed randomly on several construction panels at different points on the production line. The frequency of inspections is a function of the variability of the materials used and the stability of the production process on that line. Therefore, the bonds between the materials of different panels being inspected are not at the same stage of formation at the time of these inspections. The time it takes an operator to inspect a panel can affect the quality of the manually assessed joints. Similar inspections are also performed during the production of fiberglass-coated gypsum panels.

[0005] These prior art inspections therefore make it impossible to quantify the quality of the joints between different materials in a construction panel, much less to provide a reliable quantification that is performed identically for all construction panels in a production line.

[0006] The object of the present invention is to at least partially remedy the drawbacks of the prior art by providing a method for inspecting joints between layers of construction panels, an associated device, and a method for manufacturing construction panels incorporating such an inspection method, which allows reliable quantification of the quality of the joints between layers of construction panels. Summary of the Invention

[0007] To this end, the present invention provides a method for inspecting the joint between at least two layers of material of a construction panel formed by cutting on a production line a flow of layers of material that have been laminated and joined together to produce an edge-faced construction panel, the method comprising: The inspection method includes detecting bond failures between two layers of the material; The detecting step capturing an image of an edge surface of the construction panel; the sub-step of analyzing the image thus captured; The present invention proposes an inspection method characterized by comprising:

[0008] According to the present invention, inspection for good adhesion between a gypsum or cement layer in a construction panel and an outer layer of the construction panel made of paper or fiberglass material is carried out on panels in a production line as well, without manually tearing the outer layer of the construction panel. Image capture is used to detect spontaneous delamination of these material layers due to insufficient formation of the bond between them. Preferably, the detection step is carried out at the same point for all construction panels to be inspected in a production line. More preferably, each panel in a production line is inspected by the inspection method according to the present invention.

[0009] It should be noted that the construction panel may comprise layers of materials other than gypsum and paper or fiberglass-based materials. The present invention is applicable to any type of construction panel whose manufacture may cause problems with delamination of the layers of material. For example, the construction material may comprise an inner layer of cement coated with an outer layer of paper or fiberglass.

[0010] According to an advantageous feature of the method for inspecting joints according to the invention, the substep of capturing an image is preceded by a substep of sending a gas, for example air or water vapor, to the edge surface of the construction panel, the sending of water vapor preventing the panel from overheating during a subsequent drying step.

[0011] This gas injection substep allows for the quantification of the quality of the bond, as it promotes delamination of layers of material if they do not have a sufficiently strong bond to prevent delamination. It should be noted that this delamination occurs naturally between layers of different materials, not between two sub-thick layers of paper, as can occur when manually tearing paper from construction panels in the prior art.

[0012] According to another advantageous feature of the method for inspecting joints according to the invention, in the substep of delivering gas, the gas is delivered at a predetermined pressure of 1 to 6 bar. This relative pressure (i.e., added to atmospheric pressure) can, for example, be kept constant throughout the detection step or modulated depending on the arrival of a construction panel in front of a camera performing an image capture substep. For example, this pressure can be varied according to a pressure gradient. Advantageously, a position sensor for the construction panel on the production line can be used to interrupt the delivery of pressurized gas between two detection steps.

[0013] According to an advantageous feature of the method for inspecting a bond according to the invention, the analysis substep provides a value representative of the level of delamination between the two layers of material over at least a portion of the edge surface, the analysis substep being followed by a substep of comparison of the value representative of the level of delamination with a predetermined delamination threshold, this representative value being, for example, the maximum degree of delamination between the two layers of material visible in the captured image or the average degree of delamination between these two layers calculated following analysis of the captured image.

[0014] Preferably, if the construction panel comprises more than two material layers and thus at least two interfaces between two layers, the analysis substep provides a value indicative of the delamination level for each interface between two of the material layers of the construction panel or for both interfaces between the material layers, and each indicative value is compared with the delamination threshold value predetermined in the comparison substep.

[0015] More preferably, the comparison substep is followed by a diagnosis substep of immediately concluding that there is a bond failure if at least one reading provided by the analysis substep is greater than the peel threshold, or that there is no bond failure otherwise, this diagnosis being displayed, for example, on a screen, allowing an operator to eject the panel from the production line in case of a failure and / or to quickly adjust production line parameters.

[0016] The present invention also relates to a manufacturing method for manufacturing on a production line a construction panel comprising at least two layers of material, the method comprising: stacking the layers of material to create a flow of the stacked layers of material; forming bonds between the layers of material thus laminated; and cutting the flows of said integrally laminated and joined layers of material to form a construction panel; The present invention also relates to a manufacturing method, characterized by carrying out the inspection method according to the present invention.

[0017] In one embodiment of the invention, the layers of material that are laminated are a layer of gypsum and a layer of paper.

[0018] The forming step, like the lamination step, begins early, since the gypsum mixed with water can begin to bond with the paper when it is placed on the paper layer. This forming step, which takes advantage of the hydration of the materials, can include adding additives during the premixing of the gypsum and water. The cutting step can also be performed during this bond forming step.

[0019] Preferably, the step of forming the joint is followed by a step of drying the layer of material, and the detection step is carried out between the cutting step and the drying step, in this way panels with defects can be detected before proceeding to the drying step.

[0020] According to an advantageous feature of the method for manufacturing construction panels according to the invention, the detection step is followed by a step of ejecting the construction panel from the production line if at least one value indicative of the level of delamination provided by the analysis substep is greater than an upper threshold value. This higher threshold value corresponds, for example, to the dimensions of the inlet of the dryer used in the drying step. In this way, if the delamination is too great, the construction panel will not be sent directly to the dryer, as it would risk clogging it.

[0021] According to another advantageous feature of the method for manufacturing construction panels according to the invention, following the detection step, a step of adjusting at least one parameter of the production line is carried out depending on at least one value indicative of the level of delamination provided by the analysis step or depending on the conclusion of the diagnosis step. This parameter may be, for example, the amount of water used relative to the amount of dry gypsum in the step of mixing the amount of dry gypsum with the amount of water to form the gypsum layer prior to the step of stacking the material layers, if the material layer comprises a gypsum layer and a paper layer. This water / dry gypsum ratio is adjusted to promote the formation of a bond between the gypsum layer and the paper layer. If the diagnosis is that there is no bond failure, for example, the amount of water used relative to the amount of dry gypsum in this adjustment step may be reduced. Here, the amount of water relative to the amount of dry gypsum relates to the entire gypsum layer or to only one or more interface sublayers of the gypsum layer at the interface between the gypsum layer and one or more outer material layers of the gypsum layer. In this case, the mixing step may comprise a different mixture, for example, an initial mixture of water and wet gypsum with other dry ingredients, configured to form the inner, main gypsum layer, which is later modified to create the interface sub-layer. The term "mixture" is used broadly herein and may be understood as "preparation of the mixture."

[0022] According to an advantageous feature of the method for manufacturing construction panels according to the invention, the stacked layers of material comprise layers of gypsum, the manufacturing method comprising, at a point on the production line, a number of detection steps for different construction panels arriving successively at said point, and an analysis step providing a value indicative of a zero level of delamination for each interface between two of the stacked layers of material, followed by an adjustment step, prior to the step of stacking the layers of material, consisting of reducing the amount of water used relative to the amount of dry gypsum to form a mixture designed to form an interface sublayer of the gypsum layer or layers of the gypsum layer relative to the other of the stacked layers of material, the adjustment step being repeated after each subsequent analysis step until the subsequent analysis step provides a value indicative of a non-zero level of delamination but below the predetermined threshold. This water reduction step therefore affects the entire gypsum layer or only the interface sublayer or sublayers of the gypsum layer at the interface between the gypsum layer and one or more outer layers of material.

[0023] In one embodiment of the invention, the laminated layers of material comprise layers of gypsum; At least one of the parameters is: the ratio of the amount of an accelerator of the chemical reaction between the water and the gypsum of the gypsum layer on the one hand to the amount of a retarder of the chemical reaction between the water and the gypsum of the gypsum layer on the other hand; the amount of blowing agent injected into the mixture; the amount of superplasticizer injected into the mixture; the amount of water used relative to the amount of dry gypsum to form the mixture; a target density of the gypsum layer of the construction panel; and a target weight of the construction panel; selected from a list containing The amounts of accelerator and retarder are injected into a mixture configured to form the gypsum layer in a mixing step prior to the layering step.

[0024] In this adjustment step, multiple parameters can be adjusted simultaneously. Of course, the above list is not exhaustive. The target density is adjusted, for example, by changing the amount of foaming agent injected in the mixing step or the amount of water used relative to the amount of dry gypsum in the mixing step. This can affect the entire gypsum layer or just one or more interfacial sublayers of the gypsum layer at the interface between the gypsum layer and one or more outer layers of material.

[0025] For example, the laminated layers of material include at least one gypsum layer and a layer laminated to the gypsum layer, the gypsum layer including a sub-layer interfacing with the layer laminated to the gypsum layer; At least one of the parameters is: the ratio of the amount of an accelerator of the chemical reaction between the water and the gypsum of the interface sub-layer on the one hand to the amount of a retarder of the chemical reaction between the water and the gypsum of the interface sub-layer on the other hand; the amount of blowing agent injected into the mixture; the amount of superplasticizer injected into the mixture; the amount of water used relative to the amount of dry gypsum to form the mixture; a target density of the interface sub-layer of the construction panel; and a target weight of the interface sub-layer; selected from a list containing The amounts of accelerator and retarder are injected into a mixture configured to form the interface sub-layer prior to the laminating step.

[0026] In one embodiment of the present invention, the method for manufacturing construction panels according to the present invention comprises a number of detection steps at a point on the production line for different construction panels arriving successively at said point, each detection step being followed by a step of adjusting at least one said parameter, the adjustment step using an adjuster that receives as input the difference between the current set value of at least one said parameter of the production line and an estimated value of at least one said parameter based on at least one value indicative of the level of delamination from the detection step. In other words, in this embodiment of the present invention, the adjustment steps are carried out according to an adjustment loop, which of course uses a model that estimates values ​​for the parameters corresponding to a predetermined level of delamination. If multiple parameters are changed in these adjustment steps, the model includes as many variables as there are parameters.

[0027] Finally, the present invention provides an apparatus for inspecting the bond between at least two layers of material of a construction panel formed by cutting on a production line a flow of layers of material that have been laminated and joined together to produce an edge-faced construction panel, said inspection apparatus comprising means for detecting bond defects between two of said layers of material, The detection means means for capturing an image of the edge surface of said construction panel; means for analyzing the images thus captured; The present invention relates to an apparatus characterized by comprising at least:

[0028] Advantageously, the inspection device also comprises at least one nozzle for delivering gas at a predetermined pressure onto said edge surface of said construction panel.

[0029] Advantageously, the inspection device comprises means for detecting the position of a construction panel on the production line and means for directing gas depending on the position detected by the detection means, said gas directing means being, for example, one or more nozzles as described above.

[0030] Finally, in the inspection device according to the invention, the main direction of the gas spray by the nozzle is preferably directed facing the edge surface of the construction panel and / or parallel to the longitudinal direction of movement of the construction panel.

[0031] The inspection method according to the present invention has the same advantages as the inspection method according to the present invention and the manufacturing method according to the present invention.

[0032] Other characteristics and advantages of the invention will become apparent from the following description on the one hand and from a number of examples given without limitation with reference to the accompanying schematic drawings, in which: [Brief explanation of the drawings]

[0033] [Figure 1] FIG. 1 shows steps in a method for manufacturing a construction panel according to the invention in one embodiment of the invention. [Figure 2] FIG. 2 shows a production line for construction panels according to the invention in this embodiment of the invention. [Figure 3] FIG. 3 shows an apparatus for inspecting a joint between two material layers of a construction panel according to the present invention in this embodiment of the invention, prior to the detection step performed by the inspection apparatus. [Figure 4] FIG. 4 illustrates the inspection apparatus of FIG. 3 during a detection step performed by the inspection apparatus, in accordance with an embodiment of the present invention. [Figure 5] FIG. 5 shows images acquired by the inspection apparatus of FIGS. 3 and 4 during the detection steps performed by the inspection apparatus in this embodiment of the invention. [Figure 6] FIG. 6 shows an embodiment of a step for adjusting the parameters of the manufacturing method according to the invention in another context of an embodiment of the invention. [Figure 7] FIG. 7 shows another embodiment of steps for adjusting the parameters of the manufacturing method according to the invention in the context of another embodiment of the invention. DETAILED DESCRIPTION OF THE INVENTION

[0034] Manufacturing method 1 for producing construction panels according to the present invention, according to one embodiment of the present invention, will be described with reference to Figures 1 and 2. More specifically, in this embodiment of the present invention, manufacturing method 1 allows for the production of gypsum panels covered with a paper layer, and is carried out by production line 3 shown in Figure 2. The construction panels are thin rectangular boards. The boards comprise an inner layer of gypsum 901 (shown in Figure 5) and outer layers of paper 900, 902 on the surface of the board. Each outer layer of paper 900, 902 actually comprises multiple paper thicknesses, for example, two or three paper thicknesses.

[0035] 1 and 2, the first step in the manufacturing method of the present invention is to calcine the mineral gypsum, thereby forming gypsum, at step 80. This first step is followed by mixing the resulting gypsum with water and other compounds, as described in more detail below, at step 90. This mixing step 90 produces a wet gypsum mixture. A portion of this mixture can be removed to modify its properties, for example, with certain additives, and configured to form a gypsum sub-layer, as described below.

[0036] The next step in the manufacturing method according to the invention is step 100, in which layers of material 900, 901, 902 are stacked on the production line 3. For this, the moist gypsum mixture obtained in the mixing step 90 is spread on a first paper layer 900, its edges are folded to contain the mixture, and then it is covered with a second paper layer 902. As the materials advance on the production line 3, the thickness of the stacked layers can be modified by compressing the whole with an extruder formed by a pair of rollers.

[0037] If the mixing step 90 includes a mixture sampling step configured to form an interface sub-layer in the gypsum layer 901 with the paper layers 901, 902, the interface sub-layer having a different composition or density from the rest of the gypsum layer 901, the production line 3 includes one or more specialized rollers. These specialized rollers are used to spread a sample of the mixture, having a different composition or density from the rest of the mixture, onto the paper layers 900, 902 to form a moist gypsum interface sub-layer on each of the paper layers 900, 902. Then, in the layering step 100, the remaining portion of the mixture is spread onto the first paper layer 900, which is covered by one of the previously formed interface sub-layers. The spread remaining portion of the mixture forms an inner portion of the gypsum layer 901. The inner portion is covered by the second paper layer 902, with the other previously formed interface sub-layer disposed between the inner portion and the second paper layer 902.

[0038] In this layering step 100, a first paper layer 900, a gypsum layer 901, and a second paper layer are layered in the following order: This layering continues throughout manufacturing method 1. Thus, the layering of material layers 900, 901, 902 at the output of step 100 creates a flow of long material layers 900, 901, and 902.

[0039] The placement of the wet gypsum mixture between the paper layers 900 and 902 assists in the formation of a bond between the paper layers 900, 902 and the gypsum layer 901. Thus, the laminating step 100 is part of the step 200 of forming a bond between the layers of material 900, 901, 902. This step 200 of forming a bond is facilitated by the hydration of the gypsum and paper layers by the water from the mixing step 90. This hydration promotes the formation of gypsum crystals at the interface between the gypsum layer 901 and the paper layers 900, 902. As these solidify, they surround the fibers of the first of the paper layers 900, 902, thereby forming a bond between the paper layers 900, 902 and the gypsum layer 901. This bond ensures good adhesion between the paper layers 900, 902 and the gypsum layer 901. During the mixing step 90 prior to the layering step 100, additives or accelerators may be added to the water in the gypsum mix to promote or accelerate, respectively, this bond formation. This bond formation step 200 therefore comprises the formation of entangled gypsum crystals around the paper fibers. This formation step is completed before the construction panels 9 enter the drying step 500, in which hot air is blown onto the construction panels 9. This drying step 500 removes excess water that was added during the mixing step 90 to improve the fluidity of the wet gypsum mix.

[0040] The lamination step 100 is followed by a step 300 of cutting the flow of material layers 900, 901, 902 moving along the production line on rotating rollers 8 into rectangular construction panels 9 (shown in Figures 3 and 4). By way of example, these construction panels 9 are approximately 2.5 meters in length.

[0041] In this embodiment of the invention, the cutting step 300 is performed after the laying step 100, once the gypsum has fully hardened, and before the drying step 500.

[0042] According to the invention, the manufacturing method 1 also comprises a step 400 of detecting poor bonds between the layers of material 900, 901, 902, for example a poor bond between the gypsum layer 901 and the first paper layer 900 and / or a poor bond between the gypsum layer 901 and the second paper layer 902. This detection step is carried out at the edge faces of the construction panel 9, i.e. after the cutting step 300.

[0043] In this embodiment of the invention, the detection step 400 is carried out between the cutting step 300 and the drying step 500, i.e. in the joint formation step 200. This is in fact a "wet" detection. This "wet" detection step 400 is advantageously carried out as close as possible to the cutting device used in the cutting step 300. The purpose is, on the one hand, to make it easier to characterize the relationship between the gypsum layer 901 and the paper layers 900, 902 due to the weak adhesion between them, and, on the other hand, to allow a fast ejection of the defective board in case of a defect and a fast activation of a feedback loop allowing adjustment of the manufacturing method 1 according to the invention, as will be explained below.

[0044] In an alternative embodiment of the invention, the detection step 400 is performed after the drying step 500, in this case a "dry" detection. Of course, the two detection steps may also be combined.

[0045] Preferably, this detection step 400 is performed for all construction panels 9 moving on the production line 3 during the execution of the production method 1 according to the invention. Alternatively, the detection step 400 is performed only for a sample of the construction panels 9, for example for one construction panel 9 out of every ten construction panels 9 running on the production line 3.

[0046] The detection step 400 is a major step in the method 4 for inspecting the joint between two layers of material in a construction panel 9 and is performed in hardware and software by the inspection device 40 shown in Figures 2 and 3.

[0047] The inspection device 40 comprises at least one camera 13, which is mounted on a beam and interfaces with the computer 7 via a wireless link 14, for example a Wi-Fi connection using the IEEE 802.11 standard. Preferably, multiple cameras are used to monitor the entire edge surface of the construction panel 9. Preferably, the inspection device 40 also comprises a lighting system capable of illuminating the edge surface of the panel 9, so that when the paper layer 900 or 902 peels off from the gypsum layer 901, a shadow is formed between the paper layer 901 or 902 and the gypsum layer 901, facilitating contour detection, which is performed in the image analysis substep described below.

[0048] The inspection device 40 also comprises at least one nozzle 11 for sending gas, in this example compressed air 12, to the construction panels 9 arriving on the production line 3. In this production line 3, the construction panels are moved in a longitudinal direction L in a direction of movement 10 by rollers 8. In a cutting step 300, the construction panels 9 are cut in the direction of their width along a transverse direction T perpendicular to the longitudinal direction L and the vertical direction V.

[0049] The nozzle or nozzles 11 are preferably arranged between rollers 8 of the same section of the production line 3 in the transverse direction T, and are preferably arranged so that their air jets have a direction substantially parallel to the longitudinal direction, i.e., a direction parallel to the longitudinal direction L within a few degrees (e.g., within 10 degrees). In this way, the air jets are directed substantially perpendicular to the edge surface of the construction panel 9 produced in the cutting step 300. The nozzles 11 are arranged vertically below the camera 13 and are arranged longitudinally near the longitudinal position of the camera 13.

[0050] In this embodiment of the invention, a single nozzle 11 is preferably used, positioned vertically below the vertical position of the construction panel 9, with its air outlet forming an angle of, for example, 5° to 15° with respect to the longitudinal direction L. This allows testing both 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. This main embodiment is preferred for reasons of cost and simplicity, since only one nozzle is used and the nozzle position 11 does not need to be adjusted depending on the thickness of the construction panel 9. However, alternative embodiments are possible in which the angle is, for example, 5° to 20°, 5° to 30°, or 5° to 45°. Alternatively, the nozzle 11 may be used to test only the adhesion between the gypsum layer 901 and a single paper layer 900 or 902.

[0051] In another embodiment, a nozzle 11 is used, which is positioned vertically above the construction panel 9, with the air outlet from this nozzle forming an angle of 5° to 15°, 5° to 20°, 5° to 30°, or 5° to 45° with respect to the longitudinal direction L. The vertical position of the nozzle 11 is adjusted depending on the thickness of the construction 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, it is also conceivable to combine these variants. In this case, two nozzles are used, one positioned vertically below the vertical position of the construction panel 9 and the other positioned vertically above the vertical position of the construction panel 9.

[0052] For example, in Figure 3, the construction panel 9 contains moisture and has just passed through the cutting step 300. Air 12, which is delivered through a nozzle 11, reaches below the surface of the construction panel 9. In Figure 4, meanwhile, the nozzle 11 blows air 12 towards the edge surface of the construction panel 9, which is moving in the direction of travel 10. Preferably, this air 12 is delivered at a pressure slightly higher than atmospheric pressure, for example 2 bar. This relative air pressure 12 (i.e. added to atmospheric pressure) at the outlet of the nozzle 11 is predetermined and is between 1 and 6 bar.

[0053] The air 12 leaving the nozzle 11 is continuously delivered at the same pressure as when passing through the construction panel 9, for example.

[0054] Alternatively, if the inspection method is configured to correlate a pressure threshold with the separation 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 changes according to an increasing pressure gradient. This pressure threshold allows the level of adhesion between this paper layer 900 or 902 and the gypsum layer 901 to be quantified. This configuration is activated, for example, by an operator. The inspection device is equipped with a human-machine interface, in particular a screen that makes it possible to visualize the separation 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 measurements and diagnostics resulting from the detection step 400, as described below. These measurements and diagnostics are displayed for each construction panel 9 inspected by the inspection method according to the invention. Preferably, one diagnosis and one measurement are displayed for the bond between the first paper layer 900 and the gypsum layer 901, and another diagnosis and another measurement are displayed for the bond between the second paper layer 902 and the gypsum layer 901.

[0055] It is also preferred that the nozzle 11 delivers air 12 only when the edge surface of the construction 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.

[0056] Returning to FIG. 1, the detection step 400 comprises a first substep 410 of directing air 12 through a nozzle 11 onto the edge surface of the construction panel 9 facing the nozzle 11 .

[0057] The next substep is step 420 of capturing an image of the edge surface of the construction panel 9 by the camera 13. If the joint between the paper layer 900 and the gypsum layer 901 or the joint between the paper layer 902 and the gypsum layer 901 is insufficient to obtain good adhesion between the paper and the gypsum, the air 12 blown onto the edge surface of the construction panel 9 may cause one of the paper layers 900 or 902 to peel off from the gypsum layer 901.

[0058] Thus, capture substep 420 provides image 130, shown in Figure 5, in which delamination 921 between gypsum layer 901 and paper layer 902 potentially indicates poor adhesion between paper layer 902 and gypsum layer 901. Image 130 is displayed on the screen of inspection device 40. It can be seen that in this example application of the inspection method according to the invention, paper layer 900 has not delaminated from gypsum layer 901, indicating good adhesion between these two layers 900 and 901.

[0059] The next sub-step is an analysis step 430 of the image 130 obtained in the previous acquisition sub-step 420. This image analysis makes use of contour detection to identify the different layers of the construction panel 9 and the delaminations 921 between the paper layer 902 and the gypsum layer 901. In the analysis sub-step 430, contour detection is followed by a measurement step Dmes of the maximum delamination visible on the image 130 between the material layers 901 and 902 of the construction panel 9. This measurement indicates the level of delamination between the material layers 901 and 902 of the construction panel 9. In this analysis sub-step 430, a further contour measurement between the material layers 900 and 901 gives a zero value for the maximum delamination between these material layers 900 and 901.

[0060] In this example of the present embodiment of the present invention, it is assumed that only the second paper layer 902 peels from the gypsum layer 901, and the following description of the inspection method and manufacturing method will describe in detail the steps and sub-steps of these methods with respect to this peeling portion 921. These steps and sub-steps can also be transferred to examples where the gypsum layer 901 and the first paper layer 900 peel from each other, or where both the first paper layer 900 and the second paper layer 902 peel from the gypsum layer 901.

[0061] In an alternative embodiment of the invention, this analysis sub-step 430 provides an average value of the delamination between the paper layer 902 and the gypsum layer 901 over at least a portion of the edge surface of the construction panel 9. This average value is also indicative of the level of delamination between the material layers 901 and 902 of the construction panel 9. In another embodiment, the analysis sub-step 430 provides an area value of the delamination between the material layers 901 and 902 of the construction panel 9. This area value may also be taken as a value indicative of the level of delamination between the material layers 901 and 902 of the construction panel 9.

[0062] The next substep is step 440 of comparing the maximum peel measurement Dmes with a predetermined peel threshold S1. This predetermined peel threshold S1 is set to, for example, 2 mm (millimeters). Preferably, this predetermined peel threshold S1 is between 1 mm and 4 mm. Alternatively, the peel threshold S1 is, for example, 1 mm, 3 mm, or 4 mm.

[0063] In an alternative embodiment of the invention that utilizes the average value of the peel between the paper layer 902 and the gypsum layer 901, the comparison substep 440 compares this average value with a predetermined peel threshold S1, set at, for example, 1 mm.

[0064] The next substep is a diagnostic step 450, which concludes whether or not there is a bond failure between the layers of material measured in the analysis substep 430. In this diagnostic substep 450, if the value indicating the maximum level of the delamination in step 440 (hence the maximum delamination measurement Dmes or the average delamination value in the corresponding embodiment) is greater than a predetermined delamination threshold S1 (branch Y in the output of step 440 in FIG. 1), the diagnostic substep 450 concludes that there is a bond failure between the gypsum layer 901 and the paper layer 902. Alternatively (branch N in the output of step 440 in FIG. 1), the diagnostic substep 450 concludes that there is no bond 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 obtained in the diagnostic substep 450 is displayed on the screen of the inspection device according to the invention.

[0065] In this embodiment of the invention, if the diagnostic substep 450 concludes that there is a bond failure between the gypsum layer 901 and the paper layer 902, the detection step 400 is followed by a step 550 of comparing the value representing the maximum level of delamination with an upper threshold value S2. The upper threshold value S2 corresponds to the maximum delamination value that is acceptable for the construction panel 9 to pass through the dryer. This upper threshold value S2 may be equal to the predetermined delamination threshold value S1 (in this case, step 550 is not necessary and, as soon as a bond failure is detected, the diagnostic substep 450 is followed by a step 600 of removing the construction panel 9 from the production line 3), but is preferably strictly greater than the predetermined delamination threshold value S1. In this embodiment of the invention, this upper threshold value S2 is set to 6 mm. Alternatively, it may be set to 3 mm, 4 mm, or 5 mm, but in these variants it will always be greater than the predetermined delamination threshold value S1, which is, for example, 1 mm, 3 mm, or 4 mm, respectively.

[0066] If step S550, which compares the value indicative of the maximum level of delamination with the upper threshold S2, determines that the value indicative of this maximum level is greater than the upper threshold S2 (branch N at the output of step 550), the next step is step 600, which ejects the construction panel 9 from the production line 3. In this way, construction panels 9 with defects do not proceed to the drying step 500. Due to the narrow opening of the dryer used in this drying step 500, construction panels 9 with defects risk becoming clogged.

[0067] On the other hand, if step 550, which compares the value representing the maximum peel level with the upper threshold S2, determines that the value representing this maximum level is less than the upper threshold S2 (branch Y at the output of step 550), the next step is drying step 500.

[0068] Also, in this embodiment of the invention, the detection step 400 can be followed by a step 700 of adjusting parameters of the production line 3. This adjustment step is conditional on the value indicative of the peel level obtained in the analysis substep 430 or on the conclusion of the diagnosis substep 450. The adjustment step 700 is, for example, activated as soon as a bond failure is diagnosed in the diagnosis substep 450. In particular, one or more of the following parameters are modified in this adjustment step 700 in order to maintain the value indicative of the peel level below a predetermined threshold S1 or below another threshold S1 smaller than the predetermined threshold and corresponding to a target peel threshold: The amount of accelerator for gypsum crystal formation in the gypsum layer 901 added in the mixing step 90. Such accelerator accelerates the formation of hydrated calcium sulfate from the gypsum and calcium sulfate hemihydrate present in the water in the mixing step 90. The accelerator is, for example, a heat-resistant accelerator (HRA) such as small gypsum crystals. The amount of gypsum crystal formation retarder added in the gypsum layer 901 during mixing step 90. Such retarders, which are well known to those skilled in the art, slow down the formation of hydrated calcium sulfate during mixing step 90. Such retarders are used, on the one hand, to prevent lumps from forming in the mixing equipment used during this mixing step, which would require the production line to be stopped, and, on the other hand, to prevent the mixture obtained during this step from being too viscous to be spread on the paper layer 900. The amount of foaming agent injected in the mixing step 90. This foaming agent can form a stable or unstable foam. As this amount increases, the adhesion between the paper and the gypsum potentially decreases. Preferably, a foaming agent that produces an unstable foam or a mixture of unstable and stable foam is used. The target density of the gypsum layer 901 of the construction panel 9. The higher 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 can be increased or decreased by increasing or decreasing the amount of water used relative to the amount of dried gypsum in the mixing step 90, respectively. However, increasing this amount of water means that more energy is used in the drying step 500 of the construction panel. Therefore, preferably, rather than the density of the gypsum layer, the density of the gypsum sub-layers at the interfaces of the gypsum layer 901 to the paper layers 900 and 902, as described above in connection with the mixing step 90 and the layering step 100, is changed by changing the amount of water in these gypsum sub-layers relative to the amount of dried gypsum in these sub-layers. Another way to change the density of the gypsum layer 901 of the construction panel 9 is to inject some air into this gypsum layer using the foaming agent described above. Preferably, if the latter solution is chosen, only the density of the gypsum sub-layers at the interfaces of the gypsum layer 901 to the paper layers 900 and 902 is changed, i.e. the density of the construction panel 9 as a whole is not significantly changed. The amount of water used in the mixing step 90 relative to the amount of dry gypsum. Indeed, if this water / dry gypsum ratio falls below a critical value, the adhesion between the paper layer 900 or 902 and the gypsum layer 901 will be insufficient. On the other hand, if the water / dry gypsum ratio is too high, the strength of the paper will decrease and therefore the interface between the paper layer 900 or 902 and the gypsum layer 901 will deteriorate. Preferably, this amount of water is used as a parameter in the adjusting step 700 only if the production line 3 is equipped with the specific rollers mentioned above. The purpose is to change only the amount of water sampled in the mixing step 90 and used in the part of the mixture that will form the gypsum sub-layer at the interface of the gypsum layer 901 to the paper layers 900 and 902. The amount of additive injected in the mixing step 90 to promote bonding between the paper layer 900 or 902 and the gypsum layer 901. This amount of additive may only relate to the interface sub-layer between the gypsum layer 901 and the paper layers 900, 902. The duration of the bond formation step 200. This can be varied by adjusting the speed of the production line 3. The target weight of the construction panel 9, which is achieved in particular by changing the flow rate of air injected into the gypsum mixture in the mixing step 90. The more air is injected, the worse the adhesion between the paper male 900 or 902 and the gypsum layer 901. Preferably, this target weight is used as a parameter in the adjusting step 700 only if the production line 3 is equipped with the specific rollers mentioned above. The purpose is to change only the amount of air injected into the gypsum sub-layer at the interface of the gypsum layer 901 to the paper layers 900 and 902. The amount of superplasticizer injected into the mixture. This liquefier is an additive that can be added to the mixture formed in the mixing step 90 to make the mixture more fluid and easier to spread on the paper layers 900, 902 without adding more water to the wet gypsum mixture.

[0069] It should be noted that the gypsum and water mixture produced in step 90 advantageously also contains starch, an additive that promotes the bond between paper layer 900 or 902 and gypsum layer 901, albeit only during drying. The starch contained in the mixture migrates to the interface between the gypsum and paper layers and gels during drying step 500. Therefore, in embodiments in which detection step 400 is performed after drying step 500, the amount of starch in the mixture in step 90 can be adjusted during this step 700.

[0070] Additionally, since it is the correct balance between the amount of accelerator and the amount of retarder that improves the adhesion between the gypsum layer 901 and the paper layers 900, 902 without adversely affecting the fluidity of the wet gypsum mixture prepared in step 90, the parameters of the amount of accelerator and the amount of retarder are alternatively used in place of a parameter that is the ratio of the amount of accelerator to the amount of retarder used in mixing step 90.

[0071] In this embodiment of the invention, if the value indicating the level of delamination obtained in the analysis substep 430 is greater than the predetermined delamination threshold S1 or the target delamination threshold, several adjustment steps 700 are performed after the same number of detection steps performed successively on different construction panels 9. These adjustment steps 700 are repeated until the value indicating the level of delamination obtained in the last analysis substep 430 is equal to or less than the predetermined delamination threshold S1 or the target delamination threshold. These adjustment steps 700 change the set value Pcons of one of the above-mentioned parameters for improving the adhesion between the material layer 901 and the material layer 902, for example, the amount of water relative to the amount of dry gypsum in the mixing step 90, using an adjuster shown in FIG. 6. This adjuster is, for example, of the proportional-integral-derivative type (also called PID). This amount of water relative to the amount of dry gypsum corresponds to the amount used to form the gypsum layer 901 or the gypsum sub-layer at the interface between the gypsum layer 901 and the paper layers 900, 902.

[0072] In the adjusting step 700, the adjuster PID receives as input the difference between the current set value Pcons for the parameter of the production line 3 and an estimated value Pest for the parameter based on a value indicative of the level of stripping from the detection step 400 preceding the adjusting step 700. This estimated value Pest of the parameter, here the amount of water relative to the amount of dry gypsum, is calculated using a model that gives the amount of water relative to the amount of dry gypsum used in the mixing step 90 as a function of the value indicative of the level of stripping. This model can be obtained, for example, empirically.

[0073] In this embodiment of the invention, if the value indicating the level of delamination obtained in the analysis substep 430 is zero, i.e. if the layer of material 901 and the layer of material 902 inspected in the detection step 400 are not delaminated from each other at the edge surface of the panel 9, one or more adjustment steps 700 are performed to reduce the amount of water relative to the amount of dry gypsum used in the mixing step 90.

[0074] In this case, as shown in FIG. 7, the adjusting step 700 is repeated until the value representing the delamination level obtained in the last analyzing substep 430 is non-zero but less than or equal to the predetermined delamination threshold S1 or the target delamination threshold.

[0075] More precisely, after the analysis substep 430 of manufacturing method 1, in a first comparison substep 441 it is checked whether the value representative of the level of delamination obtained in the analysis substep 430 is zero.

[0076] In the former case (branch Y in FIG. 7), the amount of water relative to the dry gypsum used in the mixing step 90 is reduced, and this first comparison substep 441 is then repeated in the next analysis substep 430.

[0077] On the other hand, if the value indicative of the level of delamination obtained in the last analysis substep 430 is non-zero (branch N in FIG. 7), a second comparison substep 442 checks whether the value indicative of the level of delamination obtained in the last analysis substep 430 is less than or equal to a predetermined delamination threshold S1 or a target delamination threshold. In the former case (branch Y in FIG. 7), the adjustment step 700 is not repeated at least until the subsequent detection step 400 diagnoses a poor bond between the layer of material 900 and the layers of material 901 and 902, or until a value indicative of a zero level of delamination is provided. In the latter case (branch N in FIG. 7), the amount of water relative to the dry gypsum used in the mixing step 90 is increased using the adjustment loop of FIG. 6.

[0078] Naturally, the invention is not limited to the embodiments described above, and modifications can be made to these embodiments without departing from the scope of the invention.

Claims

1. 1. A method (4) for inspecting a joint between at least two layers of material (900, 901, 902) of a construction panel (9) formed by cutting on a production line a flow of layers of material (900, 901, 902) that have been laminated and joined together to produce an edge-faced construction panel, comprising: The inspection method (4) comprises a step (400) of detecting a bond failure between two layers (900, 901, 902) of the material, The detecting step (400) a substep (420) of capturing an image (130) of an edge surface of said construction panel (9); a substep (430) of analyzing the image (130) thus captured; An inspection method (4) comprising:

2. 2. The method (4) for inspecting a joint according to claim 1, characterized in that the substep (420) of capturing an image (130) is preceded by a substep (410) of directing a gas (12) onto the edge surface of the construction panel (9).

3. 3. The method (4) for inspecting a joint according to claim 2, characterized in that in the substep (410) of sending the gas (12), the gas (12) is sent at a predetermined pressure of 1 to 6 bar.

4. 4. A method (4) for inspecting a bond according to any one of claims 1 to 3, characterized in that the analysis substep (430) provides a value (Dmes) indicative of the level of delamination between the two layers of material (900, 901, 902) over at least a portion of the edge surface, the analysis substep (430) being followed by a substep (440) of comparing the value (Dmes) indicative of the level of delamination with a predetermined delamination threshold (S1).

5. 5. A method (4) for inspecting joints as claimed in claim 4, wherein the construction panel (9) comprises more than two material layers (900, 901, 902), and the analysis substep (430) provides a value (Dmes) indicative of the level of delamination for each interface between two of the material layers (900, 901, 902) of the construction panel (9), and each indicative value is compared with the predetermined delamination threshold (S1) in the comparison substep (440).

6. 6. A method (4) for inspecting a bond according to claim 4 or 5, characterized in that the comparison substep (440) is followed by a diagnosis substep (450) in which it is concluded that there is a bond failure as soon as at least one indication value (Dmes) provided by the analysis substep (430) is greater than the peel threshold (S1), or that there is no bond failure otherwise.

7. A manufacturing method (1) for manufacturing on a production line a construction panel (9) comprising at least two layers of material (900, 901, 902), comprising: a step (100) of stacking the layers of material (900, 901, 902) to create a flow of the stacked layers of material; forming (200) joints between the layers (900, 901, 902) of material thus stacked; and cutting (300) the flows of said integrally laminated and joined layers of material to form construction panels (9), A manufacturing method (1), characterized in that it carries out the inspection method (4) according to any one of claims 1 to 6.

8. 8. A method (1) for manufacturing a construction panel (9) according to claim 7, wherein the step (200) of forming joints is followed by a step (500) of drying the layers of material (900, 901, 902), and wherein the detection step (400) is carried out between the cutting step (300) and the drying step (500).

9. 9. A method (1) for manufacturing a construction panel (9) according to claim 7 or 8, wherein the layers of material (900, 901, 902) that are laminated are layers of gypsum and paper.

10. A method (1) for manufacturing construction panels (9) according to any one of claims 7 to 9 in combination with claim 4 or 5, wherein if at least one value (Dmes) indicative of the level of delamination provided by the analysis substep (430) is greater than an upper threshold value (S2), the detection step (400) is followed by a step (600) of ejecting the construction panel (9) from the production line.

11. A method (1) for manufacturing construction panels (9) according to any one of claims 7 to 10 in combination with claim 4, 5 or 6, wherein following the detection step (400), a step (700) of adjusting at least one parameter of the production line is carried out depending on at least one value (Dmes) indicative of the level of delamination provided by the analysis substep (430) or depending on the conclusion of the diagnosis substep (450).

12. The laminated layers of material (900, 901, 902) comprise a layer of gypsum (901); At least one of the parameters is: the ratio between the amount of an accelerator of the chemical reaction between the water and the gypsum of the gypsum layer (901) on the one hand and the amount of a retarder of the chemical reaction between the water and the gypsum of the gypsum layer (901) on the other hand; the amount of blowing agent injected into the mixture; the amount of superplasticizer injected into the mixture; the amount of water used relative to the amount of dry gypsum to form the mixture; the target density of the gypsum layer (901) of the construction panel (9), and the target weight of said construction panel (9), selected from a list containing 12. The method (1) for manufacturing a construction panel (9) according to claim 11, wherein the amounts of accelerator and retarder are injected into a mixture configured to form the gypsum layer (901) in a mixing step (90) prior to the layering step (100).

13. The laminated layers of material (900, 901, 902) comprise at least one gypsum layer (901) and layers (900, 902) laminated to the gypsum layer (901), the gypsum layer (901) comprising sub-layers that interface with the layers (900, 902) laminated to the gypsum layer (901); At least one of the parameters is: the ratio of the amount of an accelerator of the chemical reaction between the water and the gypsum of the interface sub-layer on the one hand to the amount of a retarder of the chemical reaction between the water and the gypsum of the interface sub-layer on the other hand; the amount of blowing agent injected into the mixture; the amount of superplasticizer injected into the mixture; the amount of water used relative to the amount of dry gypsum to form the mixture; a target density of the interface sub-layer of the construction panel (9), and a target weight of the interface sub-layer; selected from a list containing 12. A method (1) for manufacturing a construction panel (9) according to claim 11, wherein said amounts of accelerator and retarder are injected into a mixture configured to form said interface sub-layer prior to said laminating step (100).

14. The layer of material (900, 901, 902) that is laminated comprises a layer of gypsum (901), and the manufacturing method (1) comprises, at a point on the production line, a plurality of detection steps (400) for different construction panels (9) that arrive successively at said point, followed by an analysis substep (430) that provides a value (Dmes) that represents a zero delamination level for each interface between two of the layers of material (900, 901, 902), and further comprising: a step of laminating the layers of material (100) for the layer of gypsum (901) or the layer of material (902) that is laminated; 12. A method (1) for manufacturing a construction panel (9) according to claim 11 when dependent on claim 5, wherein an adjusting step (700) is performed consisting of reducing the amount of water used relative to the amount of dry gypsum to form a mixture configured to form an interface sub-layer of the gypsum layer (901) relative to the other of the layers (900, 902), said adjusting step (700) being repeated after each subsequent analysis sub-step (430) until the subsequent analysis sub-step (403) provides a value indicative of a non-zero delamination level but below the predetermined threshold (S1).

15. 1. An apparatus (40) for inspecting a bond between at least two layers of material (900, 901, 902) of a construction panel (9) formed by cutting on a production line a flow of layers of material (900, 901, 902) that have been laminated and joined together to produce an edge-faced construction panel, said inspection apparatus (40) comprising means for detecting a bond failure between two of said layers of material (901, 902), The detection means means (13) for capturing an image (130) of the edge surface of said construction panel (9); means (7) for analyzing the image (130) thus captured; An apparatus (40) comprising at least:

16. 16. The device (40) for inspecting joints according to claim 15, further comprising at least one nozzle (11) for delivering a gas (12) at a predetermined pressure to the edge surface of the construction panel (9).

17. 17. The apparatus (40) for inspecting joints according to claim 16, comprising: means for detecting the position of a construction panel (9) on the production line; and means for sending gas (12) in response to the position detected by the detection means.

18. An inspection device (40) for inspecting joints along a direction 15 or 16, in which the main direction of the gas jet by the nozzle (11) is directed facing the edge surface of the construction panel (9) and / or is directed parallel to the longitudinal direction of movement of the construction panel (9).

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