Method for inspecting tire building process and inspection system therefor

Abstract

The present application relates to a method (200) for inspecting a tyre building process comprising sequentially depositing on a drum (2) an ordered number of semi-finished product elements of N semi-finished product elements, the method comprising:-pre-determining (102) an ordered number of classes of N drum state classes, where a first class corresponds to a bare drum state, and a second class corresponds to a second drum state; and the i-th category corresponds to a drum state comprising an (i-1)-th semi-finished product element deposited at a radially outermost location, where i ranges from 2 to N; -said method comprising: prior to depositing the i-th semi-finished product element-acquiring (103) an image of the current drum state; -processing (104) the image to associate the current drum state with a current class of an ordered plurality of classes of the N drum state classes; -authorizing the deposition of said i-th semi-finished product element based on a comparison between said current category and a desired category, said desired category being an i-th category of said ordered plurality of categories.

Description

Technical Field

[0001] The present invention relates to a method for inspecting a tire building process, a corresponding inspection system, and a corresponding method and device for building a tire. Background Art

[0002] In the context of the industrial production of tires, processes for building green (i.e., unvulcanized) tires are known, in which a plurality of semi-finished elements are successively deposited on a building drum rotatable about an axis. Usually, these depositions are performed automatically by machines.

[0003] WO2012001562A1 describes a method for inspecting the deposition of semi-finished elements for the production of tires.

[0004] DE102019211023A1 describes a method for measuring joints where material layers open or overlap during the production of green tires.

[0005] Definitions

[0006] The terms "radial" and "axial", and the expressions "radially in / out" and "axially in / out" are used with reference to the radial direction and the axial direction of a tire or a building drum (hereinafter more simply referred to as "drum"), the tire being a green tire / green tire / molded tire and a vulcanized tire, i.e., the radial direction and the axial direction are the directions perpendicular to the rotation axis of the above-mentioned tire / drum and the directions parallel to the rotation axis of the above-mentioned tire / drum, respectively.

[0007] The terms "circumferential" and "circumferentially" are instead used with reference to the annular extension of the tire or the drum.

[0008] For "drum state" or similar expressions, it is intended to refer to an assembly including the drum itself and all the elements that may be deposited on the drum.

[0009] "Naked drum state" refers to a drum state consisting only of the drum itself without any elements deposited on the drum.

[0010] "Drum state category" refers to the set of all possible drum states that are homogeneous with respect to the presence of semi-finished elements.

[0011] "Semi-finished component" means any component that is incorporated into the green tire during the building steps on the drum and that serves as a precursor for all or part of a component of the finished tire. One or more (in one embodiment, all) of such semi-finished components may be wound around the entire circumferential extent of the drum. One or more (in one embodiment, all) of the semi-finished components may be radially superposed on one another, e.g., each component being deposited on top of a previously deposited component. One or more of the semi-finished components may comprise an elastomeric compound that is generally unvulcanized or consist entirely of an elastomeric compound that is generally unvulcanized.

[0012] "Component of a tire" means any part or portion thereof that is adapted to perform a function in a tire, e.g., such parts being, for example, a liner, a sub-liner, a compound, one or more carcass plies, an underbelt insert, belt plies (crossing each other and belt plies at zero degrees), a tread base layer, a tread, a bead core, a bead filler, a textile reinforcement insert (only metal or elastomeric material), an abrasion-resistant insert, a sidewall insert.

[0013] A "two-dimensional image" or "2D image" of a surface means a digital image in which the information associated with each pixel of the digital image represents the reflectivity / diffusivity and / or color of the surface, such as an image detected by a conventional digital camera (e.g., a CCD). In other words, a 2D image represents the visual appearance of the surface.

[0014] A "matrix image" means a digital image in which the pixels form a rectangular matrix of comparable lengths in two dimensions (e.g., the two dimensions differ by less than one order of magnitude, such as in a 4x3 or 3x2 format). Summary of the Invention

[0015] As part of a tire building process, the applicant has observed a need to correctly deposit semi-finished components and / or deposit semi-finished components in the correct order.

[0016] According to the applicant, methods of checking the deposition of semi-finished products based on directly or indirectly detecting the thickness and / or height profile of a radially outer layer of the drum state (such as those described in WO2012001562A1 and DE102019211023A1) may be unreliable in some cases (such as in the case of very thin and / or semi-finished components with complex patterns, such as in the case of bicycle tires), and / or result in high costs, e.g., due to the need for a protection system for protecting the personnel involved due to the use of laser radiation and / or an execution time that is not compatible with current industrial requirements.

[0017] Therefore, the applicant solves the problem of checking the correct deposition of semi-finished components in an automatic, reliable, fast manner and / or at low cost.

[0018] The applicant has found that using predefined drum state categories allows the above problems to be solved, where the current drum state is classified into one of these drum state categories by processing an image acquired before depositing the semi-finished element, and where the current category is compared with the previous category corresponding to the category of depositing the semi-finished element.

[0019] In one aspect, the present invention relates to an inspection method for inspecting a tire building process, the tire building process comprising: sequentially depositing an ordered plurality of N semi-finished elements on a drum.

[0020] The method preferably comprises:

[0021] - Predetermining an ordered plurality of categories among N drum state categories, where the first category corresponds to the bare drum state, and the i-th category (where i ranges from 2 to N) corresponds to the drum state including the (i - 1)-th semi-finished element deposited in the radially outermost position.

[0022] The method preferably comprises: before depositing the i-th semi-finished element,

[0023] - Acquiring at least one image of the current drum state;

[0024] - Processing the at least one image to associate the current drum state with the current category among the ordered plurality of categories of N drum state categories;

[0025] - Authorizing the deposition of the i-th semi-finished element based on a comparison between the current category and a desired category, the desired category being the i-th category among the ordered plurality of categories.

[0026] In one aspect, the present invention relates to a process for building a tire, the process comprising: sequentially depositing an ordered plurality of N semi-finished elements on a drum, where it is contemplated to inspect the process by the inspection method.

[0027] In one aspect, the present invention relates to an inspection system for inspecting a machine for building a tire, the machine being configured to sequentially deposit an ordered plurality of N semi-finished elements on a drum.

[0028] Preferably, the inspection system comprises:

[0029] - An image acquisition system; and

[0030] - A command and control unit, the command and control unit being programmed and configured to, before depositing the i-th semi-finished element:

[0031] - Obtaining at least one image of the current drum state from the image acquisition device;

[0032] - Process the at least one image to associate the current drum state with a current category among an ordered plurality of categories of N drum state categories, wherein the first category corresponds to a bare drum state, and the i-th category (where i ranges from 2 to N) corresponds to a drum state including the (i-1)-th semi-finished element deposited in the radially outermost position;

[0033] - Authorize the deposition of the i-th semi-finished element based on a comparison between the current category and a desired category, which is the i-th category among the ordered plurality of categories.

[0034] In one aspect, the present invention relates to a device for building a tire, the device comprising:

[0035] - A machine for building a tire, configured to sequentially deposit an ordered plurality of the N semi-finished elements on a drum, and

[0036] - The inspection system.

[0037] The applicant believes that the above features, in particular the (digital) image processing of the drum state, preferably the (digital) image processing of at least a part of the radially outermost surface of the drum state obtained before depositing the i-th semi-finished element, to associate the current drum state with a current category among an ordered plurality of predetermined N drum state categories, and authorize the deposition of the i-th semi-finished element based on a comparison between the current category and a desired category, such that the i-th semi-finished element is deposited only if the (i-1)-th semi-finished element has been correctly deposited on the drum state. This desired category is the i-th category among the ordered plurality of categories, i.e., the previous category corresponding to the category of the drum state with the last deposited i-th semi-finished element.

[0038] The applicant believes that compared with known deposition inspection logics based on measuring (e.g., directly or indirectly measuring by means of a physical probe, laser triangulation or laser ranging) the elevation profile and / or thickness of the radially outer surface of the drum state, the operating logic based on predetermined drum state categories allows obtaining a high reliability and correctness of the evaluation. In fact, according to the applicant, methods based on thickness or elevation profile may require calibration based on the diameter of the drum, or may be distorted due to local anomalies (e.g., at joints, overlaps, etc.) or very thin thicknesses, or, for example, in the case where a component does not overlap with a previously built component (e.g., for a belt) along the entire circumferential extension, may still require measurements at many points along the circumferential extension, and finally, other anomalies of the above methods may be caused by axially variable thickness.

[0039] The applicant has also verified that the classification of the drum state by image processing within the current category and the comparison of the current category with the expected category are fast (also because only one image suffices), and / or require low computational resources, complexity, and cost of the method and system.

[0040] According to the applicant, due to the low invasiveness in terms of hardware and operation, the method and system of the present invention are also suitable for implementation in existing construction machines. More specifically, this low invasiveness is also the result of the preferred use of radiation for obtaining optical images in the visible field, which does not require any additional protection for the responsible personnel.

[0041] The present invention may have one or more of the following preferred features.

[0042] In one embodiment, the acquisition, processing, and authorization are performed before each i-th element among the ordered plurality of N elements is deposited. In this way, the entire deposition process of depositing element by element is automatically inspected (independently of any downtime of the machine), for example, in order to automatically manage situations such as: semi-finished elements have not been automatically attached to the drum, and have slipped to the ground or have not been correctly positioned on the deposition feed table.

[0043] In one embodiment, the acquisition, processing, and authorization are performed under the condition of restarting from a machine downtime (i.e., any interruption of the normal automatic deposition cycle of semi-finished elements), and more preferably each time of restarting. In other words, if such a deposition must occur after a machine downtime, the inspection method is performed before depositing the i-th element. In fact, the applicant has verified that: deposition defects of elements are often associated with a machine downtime that occurs immediately before a defective deposition. For example, in the case where the operator continues to manually remove the last deposited semi-finished element or manually apply a semi-finished element after stopping the machine, the present invention ensures that the machine deposits the correct semi-finished elements in the expected order at the next restart.

[0044] Preferably, if the current category is equal to the expected category, authorization is provided to deposit the i-th semi-finished element. When the current state (i.e., the actual drum state at the time of comparison) conforms to the expected state (i.e., the drum state associated with the point in the deposition process of the machine, also referred to as the "machine state"), the process is allowed to continue.

[0045] Preferably, if the current category is different from the expected category, it is contemplated not to authorize the deposition of the i-th semi-finished element (e.g., by interrupting the construction process). More preferably, it is contemplated to generate an alarm signal.

[0046] Preferably, the pre - determination includes: for each category, obtaining a corresponding set of images of the drum state belonging to the category (for example, the number of sets is greater than or equal to one thousand), and associating the corresponding set of images with the category. This pre - determination makes use of the fact that the obtained images are related to the situation of the normal construction process, so these images are easy to find quickly.

[0047] Preferably, the processing includes processing the visual appearance of the radial outer surface of the current drum state, such as the visual appearance of a bare drum or the visual appearance of a semi - finished component in the radially outermost position. More preferably, the processing includes processing the visual appearance of the surface structure or "texture" of the radial outer surface of the current drum state. The applicant has observed that classifying by processing the structure or the visual appearance of the textured surface of the visible surface of the drum state is fast and reliable and / or requires low computing resources. In addition, this processing does not cause specific problems with positioning the camera and / or specific problems with geometric synchronization of the drum.

[0048] Preferably, a comparison of the at least one image with each set of images is provided, and the current category is more preferably associated based on a comparison between the visual appearance of the radial outer surface of the current drum state or the corresponding visual appearance of the surface structure of the radial outer surface in the at least one image and the corresponding visual appearance of the radial outer surface or the corresponding surface structure of the radial outer surface in each set of images.

[0049] Preferably, the current category is the category corresponding to the set of images having an overall visual appearance with a corresponding surface structure most similar to the visual appearance of the surface structure of the radial outer surface of the current drum state in the at least one image. In other words, the processing can mimic the function of the human brain, which classifies the presented component (bare drum or radially outermost component) by comparing the appearance of the surface structure with stored data of different possible surface structures.

[0050] Preferably, the at least one image and / or each of the images is a two - dimensional or 2D image.

[0051] Preferably, the at least one image and / or each of the images is a matrix image.

[0052] Preferably, the at least one image and / or each of the images is acquired at least in the visible spectrum.

[0053] In one embodiment, the semi - finished component is selected from the group consisting of: lower belt insert, first belt layer, second belt layer, zero - degree belt layer, tread base layer, tread, sidewall or a part thereof.

[0054] In one embodiment, the semi-finished elements are selected from the group consisting of: a lining layer, an under-lining layer, a composite material, a first ply, a second ply, a sidewall insert, a sidewall or a part thereof, a lower belt insert, an abrasion insert, a circumferential reinforcement element.

[0055] Preferably, each semi-finished element is a strip of material, for example, the length of the strip of material is equal to or (slightly) greater than the circumferential extension of the drum state before depositing the semi-finished element, or each semi-finished element is obtained by helically winding a continuous elongated element over the entire drum state.

[0056] Preferably, the inspection system includes an illumination system configured to at least partially illuminate the drum state. Description of the Drawings

[0057] - Figure 1 A tire building apparatus including an inspection system according to the present invention is schematically and partially shown in a front view;

[0058] - Figure 2 A flowchart of an inspection method according to the present invention is schematically shown. Detailed Description of the Invention

[0059] The features and advantages of the present invention will be further clarified by the following detailed description of some embodiments presented by way of non-limiting examples of the present invention with reference to the accompanying drawings.

[0060] Figure 1 The apparatus for building a tire is generally designated by the numeral 100.

[0061] The apparatus 100 includes a machine 99 for building a tire. The machine 99 includes a drum 2 rotatable about a rotational axis X (perpendicular to the Figure 1 plane) and configured to sequentially deposit an ordered plurality of semi-finished elements out of N semi-finished elements, where N is greater than or equal to 2 (and typically less than ten). Depending on the type of process used, the drum 2 may have a substantially annular or substantially cylindrical shape.

[0062] The machine 99 for building a tire and its associated operations are not further described and are illustrated as a machine of a known type, for example.

[0063] The apparatus 100 further includes an inspection system 1 for inspecting the building machine 99.

[0064] Preferably, the inspection system 1 includes an image acquisition device 10 configured to acquire an image of the current drum state 80. Exemplarily, each acquired image represents a part of the radially outermost surface of the current drum state 80 (e.g., having an angular span greater than 30° at the center, e.g., an angular span of about 90°). In this figure, the drum state 80 composed of the drum 2 and the first semi-finished element 3 directly deposited on the bare drum 2 last is exemplarily shown. Exemplarily, the image acquisition device 10 includes a tele or video 2D matrix digital camera (e.g., a camera of a known type), i.e., generally adapted to capture two-dimensional matrix digital images in visible light.

[0065] Preferably, the inspection system 1 includes an illumination system 11 configured to at least partially illuminate the drum state (e.g., two white light LED lamps arranged on opposite sides of the image acquisition device 10).

[0066] Preferably, the inspection system 1 includes a command and control unit 30 operatively connected to the image acquisition device 10 and more preferably operatively connected to the building machine 99. Preferably, the command and control unit 30 is configured and programmed to command and inspect the entire operating function of the machine 99 in a manner known per se, for example.

[0067] In Figure 1 it, the command and control unit 30 is schematically depicted as a single unit. However, the command and control unit 30 can be implemented using any suitable architecture of hardware and / or software modules. For example, the command and control unit 30 can be implemented by a plurality of hardware and software modules that are logically and / or physically different and separate from each other and operate with each other. For example, the command and control unit 30, particularly the part thereof that performs the functions of acquiring and processing images, can be integrated, in whole or in part, logically and physically into the image acquisition device 10.

[0068] The inspection system 1 and the device 100 are adapted to respectively implement an inspection method and a corresponding process for building the tire of the present invention in use.

[0069] Figure 2 A flowchart of an inspection method 200 according to the present invention is schematically shown.

[0070] For the purposes of a mere example, the second step of a two-step building process will be considered. In the first step (not shown as it is known per se), the radially innermost structure of the tyre, i.e. the carcass sleeve, is built on a drum, the carcass sleeve comprising, for example, a liner, a sub-liner (alternatively a so-called composite which generally comprises a liner, a sub-liner and an abrasion insert), one or more carcass plies, beads associated with their filler inserts, possibly a sidewall or a part thereof, and any other components (such as an underinsert, an abrasion insert, a sidewall insert and any other circumferential reinforcing elements). In the second step, the radially outermost structure of the tyre, i.e. the so-called crown sleeve, is built on a corresponding drum, the crown sleeve comprising, for example, a first belt layer, a second belt layer, a zero-degree belt layer, a tread base layer, a tread and possibly an underinsert, a sidewall or a part thereof. The two structures are then joined using the drum of the first step or another forming drum in a forming station, not shown as it is known per se. However, the invention can be applied to any building process, including a process for manufacturing the components of a tyre on the same drum.

[0071] In the example considered, the building process of the second step provides for an ordered plurality of semi-finished elements to be deposited sequentially on the drum. The ordered sequence of the semi-finished elements is as follows: a first belt layer, a second belt layer, a zero-degree belt layer, a tread. Exemplarily, the first two semi-finished elements are constituted by strips of a respective elastomeric material reinforced with textile, metallic or hybrid cords, which are parallel to each other and have, for example, a length equal to or (slightly) greater than the length of the circumferential stretch of the drum state before deposition. The zero-degree belt layer is made, exemplarily, by helically winding a continuous elongate element over the entire drum state, each turn being adjacent, for example, to the subsequent turn. The tread can be constituted, for example, by a strip of elastomeric material having a length equal to or (slightly) greater than the length of the circumferential stretch of the drum state before deposition. Each semi-finished element covers the entire circumferential stretch of the previous drum state.

[0072] Preliminarily, it is envisaged to pre-determine an ordered plurality of 102 categories of drum states, where the first category corresponds to the bare drum state and the i-th category (where i ranges from 2 to 4) corresponds to the drum state comprising the (i - 1)-th semi-finished element deposited in the radially outermost position (i.e. the last deposited). In other words, the second category, i = 2, corresponds to the drum state comprising the last deposited first semi-finished element (i.e. the first belt layer), the third category, i = 3, corresponds to the drum state comprising the last deposited second semi-finished element (i.e. the second belt layer), and the fourth category, i = 4, corresponds to the drum state comprising the last deposited third semi-finished element (i.e. the zero-degree belt layer).

[0073] For each category, the pre-determination 102 includes, for example, initially acquiring a corresponding set of images of the drum state belonging to the category (for example, the number of sets is greater than or equal to one thousand), and associating the corresponding set of images with the category. Preferably, the images thus acquired relate to the normal operating conditions of the process. In this way, four homogeneous sets of images are stored, where each set of images represents parts of the outer surface of the same corresponding drum state. The surface parts are acquired independently of the corresponding angular positions. For example, the first set of images includes 2D images of approximately three thousand bare drum parts, the second set of images includes 2D images of approximately three thousand with only the first belt layer deposited on the drum, and so on.

[0074] Exemplarily, it is assumed that the first semi-finished element (i = 1), i.e., the first belt layer, has to be deposited. In this case, the current state of the drum (i.e., the actual state) under normal operating conditions is the bare drum state belonging to the first predetermined category (i = 1).

[0075] Before depositing the first carcass belt layer, it is envisaged to acquire 103 at least one image of the current drum state from the image acquisition device 10.

[0076] In one embodiment, a single image of the current drum state is sufficient to implement the inspection method. Such an image can also advantageously be acquired independently of the angular position of the drum and without particular problems of camera positioning accuracy. In other embodiments, for example, in the case where the previously deposited semi-finished elements do not cover the entire circumferential extent of the drum, multiple images may be acquired with the drum in different angular positions, for example, four images at 90° to each other, and each acquired image is subjected to the same processing in order to introduce redundancy in the classification and / or inspect the entire surface of the drum state.

[0077] Therefore, it is envisaged to process 104 the acquired images to associate them with the current category among the ordered plurality of categories of the above four drum states. This current category represents the actual state of the drum.

[0078] Preferably, this processing takes into account the visual appearance (rather than the elevation profile) of the surface structure of the radially outer surface part of the acquired current drum state. Preferably, a comparison is made between this visual appearance and the visual appearance of the corresponding surface structure of the radially outer surface of the drum state in each set of images. Preferably, the associated current category is the category corresponding to the set of images having the corresponding surface structure that is most similar in appearance to the surface structure visible in the acquired image. For this purpose, suitable image recognition algorithms (for example, image recognition algorithms of known types) can be used, which allow, for example, training a neural network ("machine learning") with the above sets of images.

[0079] Thus, it is contemplated to compare the current category with the desired category 105, that is, the current category is the first category among the ordered plurality of categories of the above-mentioned predetermined categories. This desired category corresponds to the machine state, that is, the drum state related to the point where the machine is in the deposition process (in this case, the machine is at the point of the deposition process that requires the bare drum state).

[0080] Preferably, assuming that the current category is equal to the desired category, it is contemplated to authorize 106 the deposition of the first semi-finished element. In the case where the actual drum state conforms to the drum state required by the point where the machine is in the deposition process, the processing is allowed to continue.

[0081] Preferably, assuming that the current category is different from the desired category, it is contemplated not to authorize the deposition of the first semi-finished element (for example, by interrupting the build process), and more preferably, it is contemplated to generate an alarm signal. In this case, the operator can act on the machine interface to change the machine state to conform to the current state (this change can also be automatically introduced by the inspection system), and / or can manually intervene in the drum state to make it conform to the machine state.

[0082] The operations from step 103 to 107 can be repeated with reference to the deposition of any other semi-finished element.

[0083] These operations can be performed before depositing each i-th semi-finished element, or only in the case of each restart from a machine shutdown.

Claims

1. An inspection method (200) for inspecting a tire building process, the tire building process including sequentially depositing an ordered plurality of semi-finished elements among N semi-finished elements on a drum (2), the inspection method including: - Predetermining (102) an ordered plurality of categories among N drum state categories, wherein the first category corresponds to a bare drum state, and the i-th category corresponds to a drum state including the (i - 1)-th semi-finished element deposited at the radially outermost position, where i ranges from 2 to N; Wherein, the inspection method includes: before depositing the i-th semi-finished element, - Acquiring (103) at least one image of the current drum state; - Processing (104) the at least one image to associate the current drum state with the current category among the ordered plurality of categories of the N drum state categories; - Authorizing the deposition of the i-th semi-finished element based on a comparison between the current category and a desired category, the desired category being the i-th category among the ordered plurality of categories.

2. The inspection method according to claim 1, wherein Before each i-th element of the ordered plurality of semi-finished elements among the N semi-finished elements is deposited, the acquiring (103), processing (104), and authorizing are performed.

3. The inspection method according to any one of the preceding claims, wherein, Under the condition of restarting from a machine shutdown, the acquiring (103), processing (104), and authorizing are performed.

4. The inspection method according to any one of the preceding claims, wherein, Assuming the current category is equal to the desired category, it is contemplated to authorize (106) the deposition of the i-th semi-finished element.

5. The inspection method according to any one of the preceding claims, wherein, Assuming the current category is different from the desired category, it is contemplated not to authorize (107) the deposition of the i-th semi-finished element.

6. The inspection method according to any one of the preceding claims, wherein, The predetermining (102) includes: for each category, acquiring a corresponding set of images of the drum state belonging to the category and associating the corresponding set of images with the category.

7. The inspection method according to any one of the preceding claims, wherein, The processing (104) includes: processing the visual appearance of the radially outer surface of the current drum state.

8. The inspection method according to claim 6, comprising: Comparing (105) the at least one image with each set of images, and the current category is associated based on a comparison between the visual appearance of the radially outer surface of the current drum state in the at least one image and the corresponding visual appearance of the radially outer surface of the drum state in each set of images.

9. The inspection method according to claim 8, wherein, The current category is the category corresponding to the set of images having the overall visual appearance with the corresponding surface structure most similar to the visual appearance of the surface structure of the radially outer surface of the current drum state in the at least one image.

10. The inspection method according to any one of the preceding claims, wherein, The at least one image is a two-dimensional matrix image, and the at least one image is acquired at least in the visible spectrum.

11. The inspection method according to any one of the preceding claims, wherein, Each semi-finished element is a strip of material having a length equal to or slightly greater than the circumferential unfolding of the drum state before depositing the semi-finished element, or each semi-finished element is obtained by helically winding a continuous elongate element on the drum state.

12. The inspection method according to any one of the preceding claims, wherein, The semi-finished element is selected from the group consisting of: an underbelt insert, a first belt layer, a second belt layer, a zero-degree belt layer, a tread base layer, a tread, a sidewall or a part thereof.

13. The inspection method according to any one of the preceding claims, wherein, The semi-finished element is selected from the group consisting of: a liner, an underliner, a composite, a first ply, a second ply, a sidewall insert, a sidewall, an underbelt insert, an abrasion-resistant insert, a circumferential reinforcing element.

14. A process for constructing a tire, the process comprising: Deposit a sequence of semi-finished elements out of N semi-finished elements on the drum, wherein it is envisaged to check the process by means of the checking method according to any of the preceding claims.

15. An inspection system (1) for an inspection of a tyre building machine (99), the tyre building machine (99) being configured to deposit a sequence of semi-finished elements out of N semi-finished elements on a drum (2), the inspection system comprising: - image acquisition means (10), and - command and control unit (30), the command and control unit being programmed and configured to perform the following operations before depositing the i-th semi-finished element: - acquire (103) at least one image of the current drum state from the image acquisition means (10), - process (104) the at least one image to associate the current drum state with the current category out of a sequence of N categories of drum states, wherein the first category corresponds to the bare drum state and the i-th category corresponds to the drum state comprising the (i-1)-th semi-finished element deposited in the radially outermost position, where i ranges from 2 to N; - authorise the deposition of the i-th semi-finished element based on a comparison between the current category and the desired category, the desired category being the i-th category out of the sequence of categories.

16. The inspection system according to claim 15, the inspection system comprising illumination means configured to at least partially illuminate the drum state.

17. A device (100) for building a tyre, the device (100) comprising: - a tyre building machine (99), the tyre building machine being configured to deposit a sequence of semi-finished elements out of N semi-finished elements on a drum, and - the inspection system (1) according to claim 15.

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