Method for Marking a Tire, in Particular by Color Printing

Abstract

A tire tread (1) having a tread pattern depth Hm, with at least two longitudinally oriented grooves (31, 41, 42), at least one of them being a complex groove (31), that in the new state, is alternately external cavities (311) that open onto the tread surface and internal cavities (312) that are hidden within the thickness of the tread. The external cavities (311) have a mean longitudinal length Lm, a depth at least equal to 0.9 Hm, and are separated by internal cavities having a mean longitudinal length Li, Li being at least equal to 0.5*Lm and at most equal to 2*Lm. At least one rib (21) in the longitudinal direction and delimited by a complex groove with transverse sipes (5) made at a mean spacing Pm. The spacing Pm of the transverse sipes is at most equal to the mean longitudinal length Lm of the external cavities (311).

Claims

1. A method for marking a tire of the type comprising a tread and two sidewalls delimiting said tread, the method comprising: inflating the tire mounted on a rim, and in the inflated state of the tire, making, on at least one of the sidewalls of said tire, at least one marking which is at least partially colored, wherein during the inflation, the tire is inflated to a pressure greater than the nominal inflation pressure of said tire.

2. The method according to claim 1, wherein the tire is inflated to a pressure of between 105% and 300% of the nominal inflation pressure of said tire.

3. The method according to claim 1, wherein the tire is inflated to a pressure of between 120% and 180% of the nominal inflation pressure of said tire.

4. The method according to claim 1, wherein the inflating of the tire is carried out on the final rim of the tire.

5. The method according to claim 1, wherein the inflating of the tire is carried out on a rim made up of two half-rims.

6. The method according to claim 1, wherein said marking is made by color printing with the aid of at least one print head, in particular by inkjet color printing.

7. The method according to claim 1, wherein the tire is driven in rotation during the step of making said marking via the bore in the hub of the rim.

8. The method according to claim 7, wherein the tire is driven in rotation at a constant speed.

9. The method according to claim 1, wherein the tire is in a horizontal position or in a vertical position during the step of making said marking.

10. The method according to claim 1, further comprising deflating the tire to the nominal inflation pressure after the of making of said marking.

Description

[0049] The present invention will be understood better from reading the detailed description of an embodiment considered by way of entirely non-limiting example and illustrated by the appended figures, in which:

[0050] FIG. 1 is a partial side view of a tire that comprises a marking made on a sidewall of the tire according to one exemplary embodiment of the invention, and

[0051] FIG. 2 is a flow chart of a method for marking the tire according to one exemplary implementation of the invention.

[0052] FIG. 1 schematically shows a tire 10 comprising a tread 12 and lateral sidewalls 14 surrounding the tread on either side, only one being visible in the figure. The tread 12 comprises a tread surface intended to come into contact with a road surface during running The tire 10 is mounted on a rim 16, which is preferably the final or definitive rim intended to be mounted on the vehicle. The rim 16 comprises a hub 16a, an outer ring 16b and a plurality of spokes 16c connecting the hub to the ring.

[0053] The sidewall 14 comprises a colored marking 18. In FIG. 1, the marking 18 has been shown in grey. In the exemplary embodiment illustrated, the marking 18 forms, on the sidewall 14 of the tire, an overall annular surface in the form of a continuous ring centred on the axis of rotation of the tire. Alternatively, it is possible to provide other shapes and/or other dispositions with respect to the axis of rotation of the tire. The marking 18 may for example be discontinuous in the circumferential direction. In this case, the marking 18 may be made up of a plurality of colored zones that are spaced apart from one another on the sidewall in the circumferential direction and/or in the radial direction. The colored zones may have identical external shapes or different shapes. The colored zones may for example have square, hexagonal, rectangular or parallelogram shapes.

[0054] The marking 18 may advantageously be made on the sidewall 14 after the tire has been vulcanized, by color printing with the aid of one or more print heads, as will be described in more detail below. In a variant, it is possible to make the colored marking 18 in some other way, for example by depositing paint or varnish, or by cold or hot transfer.

[0055] The marking 18 has at least one color that is different from the generally black color of the rubbery material of the tire. The marking 18 may have several colors.

[0056] As indicated above, in order to make the marking 18, it is possible to provide inkjet color printing on the sidewall 14 of the tire. In this case, use may be made of a marking machine (not shown) comprising inkjet print heads, a support means for the tire and a means for driving said support means in rotation. The support means may be provided to allow the tire to be held in a vertical position or in a horizontal position during the printing step.

[0057] The marking machine also comprises a control unit for controlling the operation of the print heads, which may for example be in the form of a printed circuit board. The marking machine also comprises a device for drying and hardening the coat(s) of ink deposited on the sidewall, for example an ultraviolet lamp or infrared lamp, or a means for blowing hot air. For more details relating to this type of marking machine, reference may be made for example to the patent EP-B1-2 639 053.

[0058] The marking of the sidewall 14 of the tire may be obtained using the marking method in FIG. 2.

[0059] In a first step, referenced 20, the tire equipped with its rim is inflated to an inflation pressure greater than the nominal inflation pressure recommended for said tire. The tire is for example inflated to a pressure of between 105% and 300% of the nominal inflation pressure of said tire. Preferably, the inflation pressure is between 120% and 180% of the nominal inflation pressure of the tire.

[0060] Next, in a second step, referenced 22, the inflated tire equipped with its rim is mounted on the marking machine. During this step, the print heads and the drying and hardening device are moved to face the sidewall to be marked.

[0061] Next, during a third step, referenced 24, the tire is driven in rotation at a constant speed via the drive means of the marking machine.

[0062] In a fourth step, referenced 26, the print heads are positioned relative to the sidewall of the tire in a determined position. This step of positioning the print heads is controlled by the control unit.

[0063] In order to position the print heads, it is for example possible to determine the position of a reference mark provided on the sidewall of the tire. By way of indication, this reference mark may for example be provided in a protruding or recessed manner on the sidewall of the tire and be in the form of a texture that is integral with said sidewall and contrasts therewith. In this case, the marking machine comprises a system for measuring the lightness, for example a spectrocolorimeter, for determining the position of this reference mark on the sidewall of the tire depending on lightness measurements that are taken on the sidewall. To this end, the lightness measurements are transmitted by the measurement system to the control unit, which comprises all the hardware and software for determining the position of the reference mark on the sidewall on the basis of these measurements. The control unit steers the positioning of the print heads relative to the sidewall of the tire.

[0064] Then, in a fifth step, referenced 28, the color printing by the print heads is commanded in order to obtain the predetermined marking on the sidewall of the tire. The step of making the marking is therefore carried out in the inflated state of the tire at the inflation pressure value applied in step 20, which is greater than the nominal inflation pressure value of said tire.

[0065] Next, in a sixth step, referenced 30, the starting of the drying and hardening device is commanded in order to obtain the drying and the hardening of the ink deposited on the sidewall. The steering of the print heads and the operation of the drying and hardening device are controlled by the control unit. During the fifth and sixth steps, the tire is still being driven in rotation at a constant speed.

[0066] Finally, in a seventh step, referenced 32, the rotation of the tire is stopped and the tire equipped with its rim is removed from the marking machine.

[0067] After removal from the marking machine and after completion of the phase of drying and hardening of the marking, it may be possible to deflate the tire so as to return it to the nominal inflation pressure.

[0068] In the above-described marking method, the marking is made on the tire by color printing. As indicated above, it remains possible to provide other ways of obtaining the marking on the sidewall of the tire.

[0069] By virtue of the method according to the invention, in which the marking(s) is/are made in the inflated state of the tire at an inflation pressure greater than the nominal inflation pressure thereof, the quality of the marking(s) upon delivery of the tire to the consumer is improved and the appearance of surface cracks on these markings during the use thereof is reduced.