Tire tread regrooving process

Abstract

The invention relates to a method for regrooving the tread of a tire, the tire having a tread residue, the method comprising: - displaying a representation (10) of a regrooving pattern; - modifying the positioning of the representation (10) of the regrooving pattern relative to the tread residue, reducing an overlap (16) between the representation (10) of the regrooving pattern and the tread residue; and then - regrooving the tire by creating grooves at positions affected by the positioning of the representation (10) of the regrooving pattern. The invention also relates to a regrooving machine configured to implement such a method. Figure for the abstract: Figure 3

Description

Title of the invention: Method for regrooving a tire tread technical field

[0001] The invention belongs to the field of tires, and more specifically relates to a method of regrooving a tire tread, and the corresponding regrooving machine. Technological background

[0002] A tire has a tread pattern consisting of a pattern of raised features in the rubber, such as grooves and peaks, which gives the tire desired properties, such as water evacuation or road grip. Tire use causes abrasion of the tread rubber, which gradually leads to erosion of the tread pattern. The peaks become less high and the grooves less deep. The tire properties conferred by the tread pattern are progressively altered until they are no longer satisfactory. To allow monitoring of the acceptable level of tire deterioration, wear indicators are present in depressions such as grooves, generally taking the form of localized raised areas at the bottom of the tread.The condition of the tire tread is considered unsatisfactory when the distance between the top of the tread and the wear indicator becomes too small.

[0003] A tire with excessively worn tread can no longer be used to power a vehicle. As a cost-saving measure, and in order to reuse the same tire, the practice of regrooving the tread pattern has been implemented. Indeed, even though part of the tread corresponding to the crests of the tread pattern has disappeared, the tread still retains sufficient thickness to create grooves that recreate a tread pattern, allowing the tire to regain properties suitable for reuse. Regrooving a tire is therefore an operation that consists of removing rubber from the existing tread block to restore tread depth, according to a given pattern that may replicate the previous pattern or differ from it.

[0004] This re-grooving operation is usually carried out manually, using a re-grooving tool operated by an operator, as described for example in patent document EP 2 025 501 AL. The re-grooving tool includes a support with a gripping part by which the operator holds the tool in his hand. The support carries a U-shaped blade, heated by an electric current, protruding from a bearing surface on the support. The operator presses the grooving tool against the tire tread, driving the blade into the tread rubber until the bearing surface is in contact with the tread. By moving the tool with the bearing surface against the tread, the operator cuts a groove or channel into the tread rubber. The depth of the resulting grooves corresponds to the blade's protrusion beyond the bearing surface. A tread pattern is thus recreated on the tread.

[0005] Such manual regrooving is a tedious and physically demanding task. A regrooving machine has already been proposed for regrooving a profile with at least one groove in a tire tread, comprising a tire housing for holding a tire on a drive axle, which is coaxial with an axis of rotation of the tire, drive means for rotating a tire received by the tire housing around the axis of rotation during a cutting operation, a cutting device which includes a cutting head with a blade and a support device for pressing the cutting head during a cutting operation on the tread of the tire received by the tire housing, so that a blade is in the groove of the tread.

[0006] In order to obtain the expected performance of the regrooved tire, the grooves produced during regrooving must follow the arrangement dictated by the regrooving pattern. Manual regrooving only allows for very simple patterns, which do not allow for optimal performance of the regrooved tire. The use of a regrooving machine makes it possible to use more complex regrooving patterns, which thus allow for better performance of the regrooved tire.

[0007] The grooves are all the more effective when they are located in the right places on the tread, and when the regrooving pattern they must follow is correctly positioned relative to the tire's tread. However, tire positioning is not always precise, and the tire's shape can vary, particularly because wear results in a reduction in rubber thickness. It is therefore not always easy to regroove the grooves in the right place. Furthermore, a tire to be regrooved normally has some tread residue, resulting from the more or less pronounced wear of the original tread pattern. It can be advantageous to align the regrooving grooves with remaining depressions of the tread residue.If the recutting grooves do not take into account the sculpture residue, the recut sculpture may then include unwanted superfluous reliefs in relation to the desired recutting pattern. Presentation of the invention

[0008] The invention aims to provide a regrooving method for regrooving a tread pattern on a tire with grooves whose positions correspond best to the expected regrooving pattern, allowing alignment between the tread pattern residue and the regrooving pattern.

[0009] To this end, the invention proposes a method for regrooving the tread of a tire, the tire having a tread residue, the method comprising:

[0010] - a display of a representation of a re-grooving pattern;

[0011] - a modification of the positioning of the representation of the re-grooving pattern compared to the sculpture residue, reducing a misalignment between the representation of the re-carving motif and the sculpture residue; then

[0012] - a regrooving of the tire by making grooves at affected positions by positioning the representation of the re-excavation pattern.

[0013] The method according to the invention is advantageously and optionally complemented by the following various features taken alone or according to any of their various technically possible combinations: - Modifying the positioning of the re-grooving pattern representation includes moving the re-grooving pattern representation and / or deforming the re-grooving pattern representation.

[0014] - The representation of the re-grooving pattern is an image in which elements geometric shapes correspond to the grooves to be cut.

[0015] - The representation of the re-grooving pattern is displayed on a screen simultaneously with a visualization of a tire tread.

[0016] - The representation of the regrooving pattern is projected onto the tread of the pneumatic.

[0017] - The carving residue includes re-excavation pits, the re-excavation pattern includes re-excavation well markings, and the modification of the positioning of the re-excavation pattern representation includes a reduction of an overlap offset between the re-excavation wells of the sculpture residue, and the corresponding markings of the re-excavation pattern representation.

[0018] - The modification of the positioning of the representation of the re-grooving pattern includes a movement of the tire.

[0019] The invention also proposes a regrooving machine comprising a rotating shaft carrying the tire, a regrooving blade configured to cut grooves in a tread surface of the tire, display means of a representation of a regrooving pattern, means of modifying the positioning of the representation of the regrooving pattern relative to a tread residue on the tire's rolling surface, and means of regrooving control taking into account the positioning of the representation of the regrooving pattern, the regrooving machine being configured to implement the process as previously described.

[0020] The regrooving machine according to the invention is advantageously and optionally supplemented by the following various features taken alone or according to any of their various technically possible combinations:

[0021] - Means of displaying a representation of a re-grooving pattern include a camera configured to acquire a visualization of the tire tread, and a screen configured to simultaneously display the representation of the regrooving pattern with the visualization of the tire tread.

[0022] - Means of displaying a representation of a re-grooving pattern include a projector configured to project the representation of the regrooving pattern onto the tire tread. Presentation of the figures

[0023] Other features, objectives and advantages of the invention will become apparent from the detailed description below, which is purely illustrative and not limiting, and which should be read in conjunction with the accompanying drawings, given by way of non-limiting examples and on which:

[0024] - Fig. 1 schematically shows an example of a regrooving machine, according to a possible embodiment of the invention;

[0025] - Figure 2 schematically shows an example of a visualization of a strip of tire bearing, according to one possible embodiment of the invention;

[0026] - [Fig.3] schematically shows a representation of the re-grooving pattern showing a misalignment with the sculpture residue;

[0027] - [Fig.4] schematically shows the representation of the re-grooving pattern superimposed with the sculpture residue.

[0028] Throughout the figures, similar elements bear identical references. Detailed description

[0029] In the accompanying figures, the various geometric orientations are defined in an XYZ coordinate system, defined by a longitudinal or circumferential direction X, tangent to the circumference of the tire along its direction of travel, a transverse or axial direction Y, parallel to the axis of rotation of the tire, and a radial direction Z, perpendicular to the axis of rotation of the tire. The term "plane" is understood to mean A radial plane is a plane containing the axis of rotation of the tire and extending along a radial direction Z and a transverse direction Y. A radial half-plane is a plane delimited by the axis of rotation of the tire and extending along the transverse direction Y and a radial direction Z from the axis of rotation of the tire.

[0030] The method uses a regrooving machine, as illustrated in [Fig. 1]. Such a regrooving machine 100 comprises a rotating shaft 102 carrying the tire 1 along its axis of rotation extending in the transverse direction Y, and a tool holder 104 capable of accommodating and moving a measuring instrument and / or a regrooving blade facing the tread 2 of the tire 1. The tool holder 104 is preferably aligned with the rotating shaft 102 in a radial direction Z, and is movable in the radial direction Z towards the rotating shaft 102, and is preferably movable in the transverse direction Y in order to move the instrument or the blade across the width of the tire 1. The rotating shaft 102 carrying the tire 1 is preferably movable at least in the vertical radial direction Z, and is configured to drive the tire 1 in rotation.

[0031] To perform the regrooving, the regrooving machine 100 carries a regrooving blade 106 whose position relative to the tire axis is determined by the height mapping. The tire 1 is rotated around the rotating axis 102 that carries it, and the regrooving blade 106, for example U-shaped, is positioned so that its end cuts the rubber on the surface of the tread 2. A groove is then formed. If the regrooving blade 106 is held fixed, the groove is circumferential around the tire 1. The regrooving blade 106 can also be moved during regrooving, particularly in the transverse direction Y, in order to create a groove with a transverse component.To move from one groove to another, it is sufficient to raise the regrooving blade 106 in the radial direction Z, then to change the relative position between the tire 1 and the regrooving blade 106, for example by transverse translation of the tool holder 104 carrying the regrooving blade 106, by rotation of the regrooving blade 106, and / or rotation of the tire 1, to make a new groove on the surface of the tread 2.

[0032] The regrooving machine 100 also includes means 108 for displaying a representation of a regrooving pattern. The display means 108 for a representation of a regrooving pattern may include a camera configured to acquire a visualization of the tread 2 of the tire 1, typically a camera acquiring a video stream. The display means 108 may also include a screen configured to simultaneously display the representation of the regrooving pattern with the visualization of the tread 2 of the tire 1. The display means 108 for a representation of a regrooving pattern may include a projector configured to project the representation of the regrooving pattern directly onto the tread 2 of the tire 1.

[0033] Figure 2 shows an example of a tread 2 of a tire 1 whose tread pattern has been worn by the tire's rolling action. The use of a tire 1 results in progressive wear and material loss in the areas in contact with the rolling surface, typically the road. Due to the tread pattern, it is the crests 10 of the tread, i.e., the areas between the grooves 8, that wear down and progressively lose height. Conversely, the tread bases, i.e., the bottoms of the grooves 8, are not normally in contact with the rolling surface and therefore wear much less. The distance between the crests 10 and the bottoms of the grooves 8 is thus reduced, and the grooves 8 become shallower. It frequently happens that wear is not uniform on the tire, and therefore that areas of the tread 2 show a more pronounced reduction in the depth of the grooves 8 compared to other areas.

[0034] The method aims to recut the tread pattern of the tire 1 to create grooves that allow the tread to reach depths of the grooves 8 suitable for giving the tire 1 properties that enable its reuse. The recutting pattern is chosen according to the tire 1, in particular according to its type. The recutting pattern defines at least the grooves to be made in the tread. The recutting pattern may also define the paths of the recutting blade 106, including when the recutting blade 106 does not cut into the rubber of the tire 1.

[0035] The tire 1 is mounted on the regrooving machine 100 in the regrooving position, on the rotating axis 102. A representation 10 of a regrooving pattern is then displayed. The representation 10 of the regrooving pattern is an image in which geometric elements correspond to the grooves to be cut to create the regrooving pattern on the tread 2. The representation 10 of a regrooving pattern is displayed in a configuration that allows simultaneous visualization of the tread residue in the same location.

[0036] Figure 3 shows an example of the display of representation 10 of the regrooving pattern. Preferably, representation 10 of the regrooving pattern comprises a set of lines, here representing the grooves to be cut and thus the paths of the regrooving blade 106. The regrooving pattern comprises a repetition of an elementary pattern in the circumferential direction X. In this example, the regrooving pattern defines the paths of the regrooving blade, including when the regrooving blade 106 is not cutting into the tire rubber. Thus, the regrooving pattern may have transverse ends 12 outside the band of bearing, which may correspond to the path of the regrooving blade 106 when it moves relative to the tread 2 without gouging. The regrooving pattern may also include positioning markings that do not correspond to the grooves to be cut or the paths of the regrooving blade 106, but rather serve to correctly position the representation 10 of the regrooving pattern. Typically, a positioning marking is a visual indication related to a location on the tire 1, which allows for estimating an overlap offset. For example, the tread residue may include regrooving wells, and the regrooving pattern may include regrooving well markings. In an overlap without offset, the regrooving well markings cover the regrooving wells.The gap between the rebore well markings and the rebore wells indicates the overlap offset. Other positioning markings may be used, provided that these positioning markings allow for the estimation of an overlap offset.

[0037] The display as illustrated in [Fig. 3] can be performed on a display screen viewed by the operator. In this case, a camera forming part of the display means 108 acquires a visualization such as an image or a video stream of the tread 2 of the tire 1. The screen simultaneously displays the representation 10 of the regrooving pattern with the visualization of the tread 2 of the tire 1, preferably in superimposed layers. Typically, the representation 10 of the regrooving pattern has gaps in the fill, so that it is possible to distinguish the visualization of the tread 2 through the representation 10 of the regrooving pattern, which is placed over the visualization of the tread 2.It is also possible to foresee that the upper layer in representation 10 of the regrooving pattern and the visualization of the tread 2 of the tire 1 may have a transparency allowing the lower layer to be seen.

[0038] Alternatively, the display as illustrated in [Fig. 3] can result from projecting the representation 10 of the regrooving pattern directly onto the tread 2. In this case, a projector forming part of the display means 108 projects the representation 10 of the regrooving pattern. There is then a superimposition between the representation 10 of the regrooving pattern and the visualization of the tread 2 of the tire 1 which serves as a support.

[0039] Due to the typically very dark character of a tread 2, the representation 10 of the regrooving pattern preferably presents very light or bright shades.

[0040] In the example of [Fig.3], a misalignment 16 is observed between the representation 10 of the re-grooving pattern and the sculpting residue of the band of tread 2. This overlapping offset 16 is all the more noticeable when the spatial organization of the representation 10 of the regrooving pattern presents similarities with the original tread pattern, which are also found in the tread remnant. Thus, the overlapping offset 16 can be observed between all corresponding characteristic points (or minutiae) of the representation 10 of the regrooving pattern and the tread remnant of the tread 2, such as, for example, the end of a groove in the remnant and the end of a line in the representation 10, or even an angle formed by a groove and a line in the representation 10. Advantageously, a positioning marking related to a location on the tire 1 makes it easy to observe the overlapping offset 16.

[0041] The overlap offset 16 does not need to be precisely estimated or evaluated; it is sufficient to note that it exists and that it is of a sufficient magnitude to be observed. The overlap offset 16 may not be homogeneous, for example, when the representation 10 of the recarving pattern is distorted relative to the carving residue, or vice versa.

[0042] The positioning of the representation 10 of the regrooving pattern relative to the carving residue is then modified, thereby reducing the overlap 16 between the representation 10 of the regrooving pattern and the carving residue. Typically, the operator modifies a positioning parameter, resulting in a change in the positioning of the representation 10 of the regrooving pattern relative to the carving residue. This could be achieved by moving or rotating the tire 1, or by moving only the representation 10 of the regrooving pattern or the visualization of the carving residue. Alternatively, a display parameter affecting the display of the representation 10 of the regrooving pattern or the visualization of the carving residue could be modified, such as a magnification or zoom value, or a distortion.

[0043] For example, when the operator observes an overlap offset 16, the operator can use a human-machine interface, such as a touchscreen or a button, to modify the positioning of the representation 10 of the recutting pattern relative to the carving residue. Preferably, the display of the representation 10 of a recutting pattern is updated during or after the positioning modification, allowing the operator to make a further positioning adjustment to reduce the overlap offset 16 even further.

[0044] Preferably, the positioning of the representation 10 of the recutting pattern is modified until the overlapping offset 16 is no longer observed, that is, until the representation 10 of the recutting pattern is sufficiently superimposed with the sculpted residue. For example, the operator acts on the interface man-machine, observes the change in positioning of the representation 10 of the regrooving pattern resulting from the display thereof, and stops its action on the man-machine interface when it considers that the superposition is satisfactory, for example when the lines of the representation 10 of the regrooving pattern are superimposed on the hollows of the residue or when the regrooving pit markings appearing in the representation 10 of the regrooving pattern cover the regrooving pits of the tread 2.

[0045] The example in [Fig.4] shows an example of satisfactory superposition between the representation 10 of the re-carving pattern and the carving residue: if the superposition offset 16 is not totally zero everywhere, it can be considered that it is sufficiently small to ensure that some grooves will re-carve the hollows of the carving residue.

[0046] It is also possible to automate the observation of the offset 16 of superposition and / or the modification of the positioning of the representation 10 of the re-excavation pattern in relation to the sculpture residue, for example by using shape recognition algorithms.

[0047] Once the superposition is deemed satisfactory, positioning parameters are determined, such as coordinates in the XYZ coordinate system, and / or a rotation of the tire 1 typically expressed in degrees, which allow a correspondence between the position of the tire on the regrooving machine 100 and the positioning of the regrooving pattern. The tire 1 is then regrooved by cutting grooves at positions determined by the positioning of the representation 10 of the regrooving pattern.

[0048] As mentioned above, the regrooving machine 100 carries a regrooving blade 106 whose position relative to the tread 2 of the tire 1 is dictated by the regrooving pattern. Typically, in order to present the entire tread 2 to the regrooving blade 106, the tire 1 is rotated around the rotating axis 102 that carries it, and the regrooving blade 106, for example U-shaped, is positioned so that its end cuts the rubber on the surface of the tread 2 following the regrooving pattern. The regrooving blade 106 can also be moved during regrooving, in particular in the transverse direction Y, in order to create a groove having a transverse component.

[0049] Once all the grooves of the regrooving pattern have been cut into the tire 1, the tire 1 can be removed from the regrooving machine, and can be mounted on a vehicle axle.

[0050] The invention is not limited to the embodiments and variants described and shown in the accompanying figures. Modifications remain possible, in particular from the point of view of the constitution of the various technical characteristics or by substitution of technical equivalents, without going out of the field of protection of the invention.

Claims

Demands

1. Method for regrooving a tread pattern of a tire (1), the tire (1) having a tread residue, the method comprising: - displaying a representation (10) of a regrooving pattern; - modifying the positioning of the representation (10) of the regrooving pattern relative to the tread residue, reducing an offset (16) of overlap between the representation (10) of the regrooving pattern and the tread residue; then - regrooving the tire (1) by making grooves at positions affected by the positioning of the representation (10) of the regrooving pattern.

2. A method according to claim 1, wherein the modification of the positioning of the representation (10) of the re-grooving pattern includes a displacement of the representation (10) of the re-grooving pattern and / or a deformation of the representation (10) of the re-grooving pattern.

3. A method according to claim 1 or 2, wherein the representation (10) of the re-grooving pattern is an image in which geometric elements correspond to the grooves to be cut.

4. A method according to any one of claims 1 to 3, wherein the representation (10) of the regrooving pattern is displayed on a screen simultaneously with a visualization of a tread (2) of the tire (1).

5. A method according to any one of claims 1 to 4, wherein the representation (10) of the regrooving pattern is projected onto the tread (2) of the tire (1).

6. A method according to any one of claims 1 to 5, wherein the carving residue comprises re-boring wells, the re-boring pattern comprises re-boring well markings, and the modification of the positioning of the representation (10) of the re-boring pattern comprises a reduction of an overlap offset (16) between the re-boring wells of the carving residue, and the corresponding markings of the representation (10) of the re-boring pattern.

7. A method according to any one of claims 1 to 6, wherein the modification of the positioning of the representation (10) of the regrooving pattern includes a displacement of the tire (1).

8. Regrooving machine (100) comprising a rotating shaft (102) carrying the tire (1), a regrooving blade (106) configured to make grooves in a tread surface of the tire (1), means for displaying (108) a representation (10) of a regrooving pattern, means for modifying the positioning of the representation (10) of the regrooving pattern relative to a tread residue on the tread surface of the tire (1), and means for controlling regrooving taking into account the positioning of the representation (10) of the regrooving pattern, the regrooving machine (100) being configured to implement the method according to any one of claims 1 to 7.

9. Regrooving machine (100) according to claim 8, wherein the means for displaying (108) a representation (10) of a regrooving pattern comprise a camera configured to acquire a visualization of the tread (2) of the tire (1), and a screen configured to simultaneously display the representation (10) of the regrooving pattern with the visualization of the tread (2) of the tire (1).

10. Regrooving machine (100) according to claim 8, wherein the means for displaying (108) a representation (10) of a regrooving pattern include a projector configured to project the representation (10) of the regrooving pattern onto the tread (2) of the tire (1).

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