Title of Invention: MOLDING ELEMENT FOR IMPROVED PREPARATION

EFFICIENCY

FIELD OF INVENTION

(0001) The present invention relates to a molding element of a tire, in particular to a molding element for a mold used for manufacturing a tire having an intended rotational direction and/or a tire axial orientation.

BACKGROUND

(0002) For manufacturing a tire, a mold for the tire comprises several separate molding elements which, by being assembled together, define a molding space of toroidal overall shape.

(0003) In order to avoid tire appearance defects of the runout type, the radial offset between the various molding elements to be necessarily reduced, once these elements have been brought together. In order to avoid these radial offsets, care is taken to ensure perfect control over the thickness of the molding elements. In order to achieve that, it is known practice to check the thickness of the molding elements using a three-dimensional measurement apparatus.

(0004) The three-dimensional measurement apparatus comprises a fixed support bed and a sensing probe. The checking operation is performed as follows: the molding element is placed on the support bed then the moving sensing probe is used to sense various measurement zones on the molding element. By sensing suitable measurement zones, it is possible to determine the thickness of the molding element at a plurality of points. By comparing each of these measured actual thickness values with corresponding reference thickness value, it is possible to determine whether or not the molding element is compliant. (0005) In order to determine the thickness of the molding element, it is necessary to probe the molding surface on the molding element, namely that surface of the molding element that is to form the tread surface of the tread of the tire. Now, this molding surface is not completely smooth because it is encumbered with the surface treatment applied on the tread. The presence of the surface treatment therefore makes it more difficult for the three-dimensional measurement apparatus to determine the thickness of the molding element with accuracy. Thus, molding element including smooth molding surface was desirable.

(0006) WO2011/15131 1A1 discloses a molding element including measurement zone with smooth surface to address the above problem. In operation, a plurality of such molding elements is assembled to form a mold for vulcanizing and molding.

(0007) However, with such molding elements, it is not easy for operator to recognize whether the molding elements are correctly assembled or not from the appearance of the molding elements. Therefore, with respect to such molding, the efficiency in assembling operation was not high.

(0008) On the other hand, with respect to tire having an intended rotational direction and/or an intended inside-outside orientation, it is required to clearly indicate such direction and/or orientation on the tread.

(0009) It is thus an object of the present invention to provide a molding element for a mold used for manufacturing a tire, which element can improve the efficiency of the assembling operation into a mold.

(0010) Definitions: (0011) A "groove" is a space between two rubber faces/sidewalls which do not contact between themselves under usual rolling condition connected by another rubber face/bottom. A groove has a width and a depth.

(0012) An "incision" is a cut made on the contact face (tread surface) with a knife-like blade, and sometimes called as 'sipe' . The width (or thickness) of such incision on the contact face is relatively thin (that is to say less than 2.0 mm) compared to a groove. Two opposed rubber faces of such incision distant in width (or thickness) direction may contact each other, at least partially and at least during passage of ground contact.

(0013) A "radial direction" is a direction perpendicular to an axis of rotation of a tire. This direction is the direction of the thickness of a tread.

(0014) A "transverse direction" is a direction parallel to an axis of rotation of a tire.

(0015) A "circumferential direction" is a direction tangent to any circle centered on an axis of rotation of a tire. This direction is perpendicular to both the radial direction and the transverse direction.

(0016) A "surface treatment" is a processing made on contact face subjected for improving tire's performance at new (initial) state, as for example forming a plurality of fine grooves (or fine ribs) on the contact face as expressed in document JPH07- 186633A, or forming a micro roughness made onto a mold for manufacturing a tire by, for example machining, electrolytic corrosion processing, etching, shot blasting etc. and such roughness being transferred to the contact face of the tire as expressed in document JPH07-2571 1 1 A.

SUMMARY OF THE INVENTION (0017) To meet this need, present invention provide a molding element for a mold used for manufacturing a tire having an intended rotational direction and/or a tire axial orientation, the molding element having an inner molding surface for a tread including a treated mold surface with predetermined unevenness so as to form a contact face of the tire as a treated tread surface which improves performance of the tire during break-in period, the molding element comprising at least one measurement zone being devoid of the predetermined unevenness and placed in the treated mold surface, the measurement zone indicates at least one of the intended rotational direction and a tire axial orientation.

(0018) According to this arrangement, when assembling these molding elements into a mold, an operator can easily confirm whether the molding elements are correctly assembled by checking a direction indicated by the measurement zone. Thus, efficiency in assembling the mold from plural molding elements having the measurement zone will be enhanced.

(0019) A surface in the measurement zone is a smooth surface which being devoid of the unevenness and has different surface texture from rest of the molding surface. It is easy for the operator to visibly know a direction indicated by the measurement zone.

(0020) Preferably, the measurement zone includes a portion enable to encompass a circle with a diameter of at least 3 mm.

(0021) According to this arrangement, it is easy to visibly confirm the measurement zone. In addition, a molding element can easily receive measurement means to check a thickness of the molding element.

(0022) Preferably, an area of the measurement zone is at most equal to 5% of whole area of the molding surface. (0023) According to this arrangement, since enough area of the treated tread surface can be obtained on the tread to be molded, the tire performance in break-in period can be maintained.

(0024) This area of the measurement zone relative to whole area of the molding surface is preferably at most equal to 3%, and more preferably between 0.01% and 2%.

(0025) Preferably the treated mold surface has a plurality of fine ribs to mold fine grooves on the tread of the tire to be molded. Preferably, the fine rib has a height of between 0.005 and 1mm, a width of between 0.01 and 0.3mm, and a pitch between the fine ribs of between 0.1 and 2mm.

(0026) Preferably, the treated mold surface has a roughness (Ra) of between 0.005 and 0.02mm.

(0027) Preferably, the molding element comprises two edges delimiting the molding surface in a circumferential direction of the tire, each of the edges is adapted to engage to an edge of another molding element and a distance between a center of the measurement zone and one of the said edges is at most equal to 15 mm.

(0028) Most of the appearance defects of the runout type are the result of a radial offset between the edges on the adjacent molding elements. According to this arrangement, since the measurement zone is located near the edge of the molding element, it is possible to check the compliance of the thickness of the molding element in this edge area. If this distance is greater than 15mm, accuracy of compliance of the thickness of the molding element will be decreased.

(0029) Preferably, at least a part of edge of the measurement zone is provided with a bordering. (0030) According to this arrangement, better visibility of the measurement zone can be obtained by emphasizing contours of the measurement zone. Such bordering can be made, for example by fine grooves, fine ribs, a protrusion, a plurality of strands (as expressed in document WO2007045425A1). The bordering can be in a form of one continuous line or combination of several lines, dashed line, dotted line, double line, or combination of these lines.

(0031) Preferably, the bordering is made by a blade.

(0032) According to this arrangement, by modifying a height of the blade, the measurement zone is able to provide feature on the tire for providing information, for example timing for tire rotation.

BRIEF DESCRIPTION OF THE DRAWINGS

(0033) Other characteristics and advantages of the invention arise from the description made hereafter in reference to the annexed drawings which show, as nonrestrictive examples, of the embodiments of the object of the invention.

(0034) In these drawings:

(0035) Fig.1 shows a schematic view of a molding element according to a first embodiment of this invention;

(0036) Fig.2 shows an enlargement of a portion indicated as II in Fig. l;

(0037) Fig.3 shows variants of a measurement zone shown in in Fig.1 ;

(0038) Fig.4 shows a schematic view of a molding element according to a second embodiment of this invention;

(0039) Fig.5 shows measurement zone according to a third embodiment of this invention;

DETAILED DESCRIPTION OF THE INVENTION (0040) Preferred embodiment of the present invention will be described below with reference to the drawings.

(0041) A molding element according to a first embodiment of the present invention will be described referring to Figs.1 and 2. Fig. l shows a schematic view of a molding element, and Fig.2 shows an enlargement of a portion indicated as II in Fig 1.

(0042) A plurality of molding elements 1 is assembled into a mold which is used for curing/vulcanizing of a tire. The molding element 1 has an inner molding surface for molding a tread of a tire.

(0043) The inner molding surface includes a molding surface (treated mold surface) 2 being provided with a plurality of ribs 3 for forming a plurality of grooves on a tread of a tire molded using the molding element 1. One of ribs extends in a tire circumferential direction and the others extend generally in a tire axial direction.

(0044) A molding surface 2 of the molding element 1 includes a plurality of fine ribs 6. These fine ribs 6 form fine grooves on the tread to be molded. The tread with such fine grooves has a treated tread surface for improving initial performance of tire during break-in period.

(0045) The sizes of such fine rib 6 are for example 0.005-1.5mm in depth (radial direction), 0.01-1.0mm in thickness and 0.1-2.0mm in pitch (distance between two adjacent fine ribs).

(0046) The tread molded by the molding element 1 has an intended direction of rotation, such intended rotation direction is indicated on a sidewall of the tire by, for example an arrow-like marking combined with a letters "ROTATION" (not shown). (0047) The molding surface 2 is provided with a plurality of measurement zones 4 being devoid of the surface treatment. The measurement zones 4 have predetermined unevenness and the fine ribs 6 are not provided in the measurement zones 4. The measurement zone 4 has an arrow-like shape for indicating an intended rotation direction of the tire.

(0048) The measurement zone 4 is positioned at a location close to one of two edges 9, 10 of the molding element 1 delimiting the molding surface 2 in the circumferential direction. These edges are adapted to come into contact with an edge of adjacent molding element to form a whole mold. A distance between a center of the measurement zone 4 and one of the edges 9, 10 is at most equal to 15mm (equal to or less than 15mm).

(0049) The measurement zone 4 is provided with both sides of the rib 3 extending in the circumferential direction. All the measurement zones 4 on the molding surface 2 are indicating the same tire circumferential direction (intended rotational direction).

(0050) A total area of the measurement zones 4 on the molding element 1 is at most equal to 5%, preferably at most equal to 3%, and more preferably at most equal to 2% and at least equal to 0.01% of whole area of the molding surface 2.

(0051) The measurement zone 4 contains a portion enable to encompass a circle 4c with diameter of 3mm, and has a bordering 5 in a form of continuous line by fine ribs or a blade.

(0052) In this embodiment, the measurement zone 4 has a shape that indicates the tire circumferential direction and that is devoid of the fine ribs 6. The measurement zone 4 has different surface texture from the molding surface 2 having the fine ribs 6. Treated tread surface including fine grooves formed by the fine ribs 6 improves performance of the tire during the break-in period. (0053) The operator can easily confirm whether the molding elements 1 have been correctly assembled with each other and/or whether the molding element 1 has been correctly assembled with a molding element for sidewall when the molding elements are assembled into a mold, because the operator easily recognize the shape of measurement zone 4 due to the difference in reflection between the measurement zone 4 and rest of the inner molding surface (that is, treated surface). Thus, preparation efficiency of the mold comprising the molding element having the measurement zone will increase.

(0054) The difference in reflection between the measurement zone 4 and rest of the molding surface 2 is further emphasized, as the measurement zone 4 contains a portion enable to encompass the circle with diameter of 3mm, which provides better visibility of the measurement zone 4.

(0055) With this arrangement, a mounting element for molding a tire having the measurement zone 4 is able to maintain an area to receive a measurement means to check a thickness of the molding element. This effect is still further emphasized as the measurement zone 4 is provided with the bordering 5.

(0056) The total area of the measurement zone 4 on the molding element 1 is maintained being at most equal to 5%, preferably at most equal to 3% and more preferably at most equal to 2% and at most equal to 0.01% of whole area of the molding surface 2. Therefore, it is avoidable to impair the performance of the tire during break-in period.

(0057) The form and orientation of the fine ribs 6 is not limited to straight line extending in the tire axial direction. The fine ribs 6 can extend in the tire circumferential direction or an oblique direction in wavy, zig-zag and/or an arc manner. Combination of several types of the fine grooves can also be applicable. (0058) As the measurement zone 4 is provided closer to two edges 9, 10 delimiting the molding surface 2 in the circumferential direction, each of the edges 9, 10 is adapted to come into contact with an edge of another molding element. A center of the measurement zone 4 is distant from one of the edges 9, 10 preferably by at most equal to 15mm for increasing accuracy of compliance of the thickness of the molding element 4.

(0059) A variation of the first embodiment of the present invention will be described referring to Fig.3. Fig.3 shows variants 4A-4C of the measurement zones 4 shown in Fig.2.

(0060) As shown in Fig.3(A), the measurement zone 4A can be applied along the circumferential rib 3 A onto the molding surface 2A. The molding surface 2 A provided with a roughness (Ra) of between 0.005mm and 0.02mm.

(0061) The roughness (Ra) can be obtained, for example by a special surface treatment operation to the molding surface 2, such as sandblasting.

(0062) The roughness (Ra) of the measurement zone 4A is, for example, between 0.002mm and 0.003mm which corresponds to an initial surface finish of the molding element without surface treatment. The roughness (Ra) of the measurement zone 4A is the surface finish of the molding element when such element is separated from a plaster mold form.

(0063) As shown in Fig.3(B), the measurement zone 4B provided in a molding surface 2B can have a simple triangle shape connected to the rib 3B. The measurement zone 4B has a bordering 5B therearound. A tip end of the triangle shape is substantially directed to the intended rotational direction of the present tire. By combining the triangular shaped measurement zone 4B with the circumferential rib 3B, the measurement zone 4B can indicate one direction similar to an arrow. (0064) As shown in Fig.3(C), a measurement zone 4C with a bordering 5C is provided along a circumferential rib 3C and has a double sided allow shape. The measurement zone 4C is formed on a molding surface with the roughness (Ra). However, any other shape indicating an orientation can be used for a measurement zone in the present invention.

(0065) A shape of the measurement zone is not limited to the allow having single sided allow-head. A shape having double sided allow-head can also provide the same advantage described above. Any shape indicating an orientation is applicable as the shape of the measurement zone.

(0066) The bordering 5C provides better visibility of the measurement zone by emphasizing contours of the measurement zone so as to improve the efficiency in mounting operation.

(0067) The bordering 5B and 5C in Fig.3(B) and 3(C) is formed by one fine rib or blade. The bordering may also be made, for example by fine ribs, a protrusion, groove, a plurality of strands as expressed in document WO2007045425A1. The bordering can be formed so as to be seen as one continuous line or combination of several lines, dashed line, dotted line, double line or combination of these lines.

(0068) A molding element according to a second embodiment of the present invention will be described referring to Fig.4. Fig.4 shows a schematic view of a molding element 21 of the second embodiment of this invention.

(0069) The molding element 21 according to this embodiment comprises a plurality of ribs 23 for forming a plurality of grooves on a tread of a tire molded using the molding element 21. One of ribs extends in the circumferential direction and the others extend in the tire axial direction. Those ribs extending in the tire axial direction are placed in an asymmetrical manner to boundary of the rib 23 extending in the tire circumferential direction.

(0070) A molding surface 22 of the molding element 21 being provided with a roughness (Ra) of between 0.005mm and 0.02mm as a surface treatment for improving initial performance of tire molded by the molding element 21. The roughness (Ra) is according to standard ISO 4287: 1997 and JIS B 0601.

(0071) This molding element 21 has a specified inside-outside orientation in the tire axial direction. Such orientation is indicated on a sidewall of the tire by, for example letters "OUTSIDE" (not shown).

(0072) A plurality of measurement zones 24a, 24b is formed on the molding surface 22. The measurement zones 24a, 24b are formed by being devoid of the treated mold surface (roughness). In the second embodiment, measurement zone have different shapes, that is triangle shape 24a and an arrow-like shape 24b. Both of them are directing to the tire outside orientation.

(0073) A total area of the measurement zones 24a, 24b on a molding surface 22 is at most equal to 5%, preferably at most equal to 3% and more preferably at most equal to 2% and at least equal to 0.01% of whole area of the molding surface 22.

(0074) Each measurement zone 24a, 24b has a size which contains a portion enable to encompass a circle 24c with a diameter of at least 3 mm.

(0075) A molding element according to a third embodiment of the present invention will be described referring to Fig.5.

(0076) Fig.5 is an enlarged view of the measurement zone of the third embodiment similar to Fig.3. (0077) A plural pairs of measurement zones 34a, 34b shown in Fig.5 (A) is provided along the circumferential rib 33 on a molding surface 32 (only one pair is shown in Fig.5 (A)). The measurement zones 34a, 34b are formed by being devoid of the roughness (Ra).

(0078) One measurement zone 34a in Fig.5(A) has an arrow-like shape with single-sided arrow head without bordering and indicates the tire axial orientation of tire to be molded. Another measurement zone 34b has an arrow-like shape with a double-sided arrow head and including the bordering 35 of a continuous line and indicates the tire rotational direction of tire to be molded.

(0079) A plural pairs of measurement zones 44a, 44b shown in Fig.5 (B) is provided along a circumferential rib 43 on a molding surface 42 (only one pair is shown in Fig.5 (B)). The measurement zones 44a, 44b are formed by being devoid of the fine ribs on a molding surface 42.

(0080) One measurement zone 44a indicates a tire axial orientation (left-right direction in Fig.5) and the another measurement zone 44b indicates a tire rotational direction (up-down direction in Fig.5)

(0081) The pair of the measurement zones 44a, 44b in Fig.5(B) have an arrow-like shape with single-sided arrow head provided with bordering 45 of dotted lines

(0082) In this embodiment, the measurement zones 44a, 44b can be applied also to a tread for a tire having both intended rotation direction and inside-outside orientation specified, providing increased mounting operation efficiency as described above.

(0083) Although two different arrows are used for indicating the rotational and axial directions in the embodiment shown in Fig.5(A), the same arrows can be used for indicating the rotational and axial directions as shown in Fig.5(B). Further, the pair can be a combination of a measurement zone with bordering and a measurement zone without bordering

(0084) In this embodiment, the measurement zone can be applied also to a molding element for molding a tread for a tire having both the intended rotation direction and inside-outside orientation specified, providing increased preparation efficiency as described above.

(0085) The pair of the measurement zones can be a combination of the same shape, as shown in Fig.5(B), combining with the same bordering, both without bordering, combination of two different bordering or combination of with bordering and without bordering.

(0086) The molding element of the present invention can be used not only for molding a pneumatic tire but also for molding a tread portion of non-pneumatic tire such as a solid tire or a tire with flexible spokes (such as a non-pneumatic tire known under the trade name "TWEEL" (registered trade mark)).

(0087) The invention is not limited to the examples described and represented and various modifications can be made there without leaving its framework.