JP2008114567A - Method and apparatus for manufacturing pneumatic tire and pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To strongly suppress the situation that cracks are generated on the outer surface of the side tread which is formed by winding a rubber strip. <P>SOLUTION: In the case the side tread is formed by winding many times the rubber strip in the state wherein the strip is overlapped while being shifted to the width direction, many V grooves are formed in the outer surface of the side tread. On the outer surface of the side tread, a sheet-like member 56, which is fairly lowered in viscosity than at the time of ordinary temperature by being heated, is supplied from the screw type heating machine 50 and bonded by pressure. The sheet-like member 56 easily infiltrates into the whole area of the V grooves to completely bury them, and this strongly suppresses the generation of the cracks in the side tread. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

    The present invention relates to a method and an apparatus for manufacturing a pneumatic tire having a side tread formed by winding a rubber strip, and a pneumatic tire.

As a conventional method for manufacturing a pneumatic tire, for example, a method described in Patent Document 1 below is known.
JP 2004-50985 A

  This is made by forming a side tread by winding the rubber strip on the outer side of the substantially toroidal carcass layer while overlapping the rubber strip in the width direction, and then narrowing the outer surface of the side tread. A belt-like room-like sheet-like member is attached to cover the V-groove formed by the adjacent rubber strip from the outside, and then the green tire having the side tread is vulcanized. The sheet-like member covering the side tread reduces the strain external force generated in the side tread when the tire rolls, thereby suppressing cracks caused by stress concentration on the side tread, particularly the bottom of the V groove. .

    However, in such a conventional method for manufacturing a pneumatic tire, although a sheet-like member is attached to the outer surface of the side tread, the rubber constituting the sheet-like member may flow even by vulcanization. It was difficult to fill up to the bottom of the V-groove, and space often remained near the bottom of the V-groove. As a result, when the tire is loaded and rolled with the space remaining at the bottom of the V-groove in this way, stress concentration due to the bending of the side wall is repeatedly generated at the bottom of the V-groove, and the side tread There was a problem that the generated cracks could not be sufficiently suppressed.

  An object of the present invention is to provide a pneumatic tire manufacturing method and apparatus and a pneumatic tire capable of strongly suppressing the occurrence of cracks on the outer surface of the side tread.

    The first purpose is to form a side tread by winding the rubber strip on the outside of the carcass layer in a state of being overlapped while shifting in the width direction, and on the outer surface of the side tread. A step of supplying and pressure-bonding a sheet-like member made of hot unvulcanized rubber to fill a V groove formed by an adjacent rubber strip, and a step of vulcanizing the green tire having the side tread. It can be achieved by the manufacturing method of the pneumatic tire,

  Secondly, side tread forming means for forming a side tread by winding the rubber strip on the outside of the carcass layer while being overlapped while shifting in the width direction, and the outer surface of the side tread was heated. Supply pressure bonding means for supplying and pressure-bonding a sheet-like member made of unvulcanized rubber to fill a V-groove formed by an adjacent rubber strip, and vulcanization means for vulcanizing the green tire having the side tread This can be achieved by a pneumatic tire manufacturing apparatus.

  In this invention, a sheet-like member made of unvulcanized rubber that has been heated is supplied to the outer surface of the side tread formed by winding the rubber strip many times in a stacked state while shifting in the width direction. Since the sheet-like member is pressure-bonded, the low-viscosity rubber constituting the sheet-like member easily flows into the entire V-groove, so that the V-groove is made of the sheet-like member rubber to the groove bottom. As it is completely buried and disappears, the outer surface of the part is smoothed. As a result, even when such a tire is loaded and rolled, stress concentration due to the bending of the side wall portion does not occur repeatedly in the side tread (V groove), thereby causing cracks on the outer surface of the side tread. It is possible to strongly suppress the occurrence of.

  Here, between a position M separated from the bead heel by 50% of the tire cross-section height H radially outward and a position N separated by 75% of the tire cross-section height H radially outward, there is a load rolling. Since large bending (surface distortion) occurs, cracks are likely to occur. However, if the sheet-like member is supplied and pressure-bonded as described in claim 2, the generation of the cracks can be effectively suppressed.

  According to the third aspect of the present invention, the V-groove can be completely disappeared, and a useless increase in tire weight can be prevented. Furthermore, if comprised as described in Claim 4, it can be made to flow easily to the groove bottom part of a V-groove by pressure bonding, hold | maintaining a sheet-like member in a desired shape.

Embodiment 1 of the present invention will be described below with reference to the drawings.
In FIG. 1, reference numeral 11 denotes a pneumatic radial tire mounted on a passenger car, a truck, a bus, and the like. The pneumatic tire 11 has a pair of bead portions 13, and bead cores 12 are embedded in the bead portions 13. ing. The pneumatic tire 11 includes a sidewall portion 14 extending substantially radially outward from the bead portion 13 and a substantially cylindrical tread portion 15 that connects the radially outer ends of both sidewall portions 14. And further.

  Reference numeral 18 denotes a carcass layer that extends between the bead cores 12 in a toroidal manner and reinforces the side wall portions 14 and the tread portions 15. It is. The carcass layer 18 is composed of at least one carcass ply 19 here, and this carcass ply 19 intersects the tire equator S at a cord angle of substantially 90 degrees, that is, substantially radial. A plurality of non-stretchable reinforcing cords extending in the direction (meridian direction), for example, steel cords, are covered with a coating rubber.

  A belt layer 20 is disposed outside the carcass layer 18 in the radial direction. The belt layer 20 is formed by laminating at least two (here, two) belt plies 21 in the radial direction. The ply 21 is formed by coating a plurality of non-stretchable parallel reinforcing cords made of, for example, steel or aromatic polyamide with a coating rubber. The reinforcing cords constituting the belt ply 21 are inclined at a cord angle of about 15 to 50 degrees with respect to the tire equator S, and the inclination direction of at least two belt plies 21 is opposite.

  Reference numeral 22 denotes a top tread made of rubber disposed on the radially outer side of the carcass layer 18 and the belt layer 20, and a plurality of main grooves 23 extending in the circumferential direction are formed on the outer surface of the top tread 22. However, lateral grooves that intersect with the main grooves 23 may be further formed on the outer surface. 26 is a side tread made of rubber disposed on both outer sides in the axial direction of the carcass layer 18, and the radially outer ends of these side treads 26 overlap the top tread 22, while the radially inner end thereof is a bead core. It overlaps with the filler 27 attached to 12.

  In this embodiment, the radially outer end of the side tread 26 is covered from the outside by the axially both outer ends of the top tread 22 and the belt layer 20, but the radially outer end of the side tread 26 The outer ends of the top tread 22 in the axial direction may be covered from the outside, and the outer ends in the radial direction of the side tread 26 are covered with the axially outer end of the belt layer 20 and the axially outer end of the top tread 22. You may end between.

  28 is a thin and thin rubber coating layer made of the same material as the rubber constituting the side tread 26. This rubber coating layer 28 is formed on the outer surface of the side tread 26 (outside in the axial direction) as described later. The outer surface is covered from the outside in the axial direction by being supplied and pressure-bonded to the side surface. Further, 32 is an inner liner disposed inside the carcass layer 18, and 33 is a rubber chafer disposed around the bead core 12.

Next, a method for manufacturing the pneumatic tire 11 as described above will be described.
First, a rotatable cylindrical first molding drum (not shown) that can be enlarged / reduced in diameter is rotated in an expanded state, and an inner side is formed outside the rotating first molding drum by a so-called constant width strip method. The liner 32 is formed. Here, the constant width strip method refers to a constant width strip formed by rubber coating a small number of aligned reinforcing cords, or a constant width strip composed only of rubber in a predetermined length one after another. After cutting to form a constant-width strip, the strip is repeatedly supplied on the forming drum while being shifted in the circumferential direction by the approximate width of the strip in a state parallel to the axis or inclined with respect to the axis. In this method, a large number of pieces are joined in the width direction to form a cylindrical tire component.

  Next, a pair of inner chafers 36 straddling both axial ends of the inner liner 32 are formed by sticking a belt-like rubber sheet on the outer side of the inner liner 32. Thereafter, a cylindrical carcass layer 18 (carcass ply 19) is formed on the first forming drum, specifically, on the outer side of the inner liner 32 and the inner chafer 36 by the constant width strip method.

  The inner liner 32 and the carcass layer 18 are formed by forming a sheet having a length corresponding to one round of the first molding drum on the transfer drum different from the first molding drum by the constant width strip method. You may make it shape | mold by transferring to a 1st shaping | molding drum from a transfer drum. Next, the first molding drum with the carcass layer 18 and the like mounted on the outside is moved and inserted into a conveying device (not shown) holding the pair of bead cores 12 with fillers 27 by suction.

  As a result, the bead cores 12 with the fillers 27 are respectively set at predetermined positions outside the both ends of the carcass layer 18 in the axial direction. Next, the cylindrical carcass layer 18 and the like are gripped from the outside by the transport device, while the diameter of the first molding drum is reduced, and the carcass layer 18 and the like are transferred from the first molding drum to the transport device. Next, the transfer device holding the carcass layer 18 and the like is moved. This movement stops when the carcass layer 18 and the like reach a position surrounding the second forming drum 37 having a reduced diameter from the periphery.

  Here, as shown in FIG. 2, the second forming drum 37 is arranged in the circumferential direction and is similarly arranged in the circumferential direction and can be expanded and contracted, together with a pair of core bodies 40 made of a plurality of rigid body segments arranged in the circumferential direction. A pair of beadlock bodies 41 composed of a plurality of rigid segments, a plurality of folding rods 42 arranged on both outer sides in the axial direction of the beadlock body 41 and arranged side by side in the circumferential direction, and an outer side in the radial direction of the core body 40 And a center bladder 43 that bulges and deforms radially outward by being filled with internal pressure, and shows the core body 40 on one side in the axial direction and the other side in the axial direction, the bead lock body 41, and the folding rod 42. Each is supported by a pair of sliders not shown.

  When the transport device moves to the position described above, the bead lock body 41 is expanded in diameter to grip the bead core 12 from the radially inner side. Next, after the carcass layer 18 and the like are transferred from the transfer device to the second forming drum 37, the transfer device is moved to return to the initial position. Next, the center bladder 43 is filled with internal pressure to bulge the center bladder 43, while the pair of sliders are moved inward in the axial direction to expand the diameter of the pair of core bodies 40 and the bead lock body. 41. The bead cores 12 are brought close to each other, and the carcass layer 18 and the like located between the bead cores 12 are bulged and deformed outward in the radial direction so as to have a substantially toroidal cross section.

  At this time, the axially outer end of the folding rod 42 is pushed inward in the axial direction by a pressing mechanism (not shown), thereby swinging the folding rod 42 so as to expand about the axially outer end. As a result, the carcass layer 18 positioned on both outer sides in the axial direction from the bead core 12 is folded around the bead core 12 with the filler 27 while being pressed against the core body 40 whose diameter is expanded by the inner end in the axial direction of the folding rod 42.

  Next, while rotating the second forming drum 37, side treads 26 are formed on both outer sides in the axial direction of the substantially toroidal carcass layer 18 by a so-called ribbon lamination method. Here, the ribbon laminating method refers to a method in which a rubber strip continuously extruded from an extruder or the like, or wound once on a reel after extrusion is supplied to a cylindrical or toroidal forming drum or the like and spiraled. Is a method of forming a tire constituent member having a predetermined cross-sectional shape.

  In this embodiment, the side tread 26 is supplied to a rotating second molding drum 37 with a thin and thin rubber strip 46 extruded from a well-known extruder (not shown), and a carcass layer is formed by a stitching roller. Molded by winding a number of times while pressing on 18 At this time, the rubber strip 46 is spirally wound while shifting in the width direction toward the radially inner side or radially outward (shifting in the radial direction of the tire in the middle of molding). It is set as the state which overlapped by the predetermined overlap amount. The aforementioned extruder and stitching roll constitute a side tread forming means for forming the side tread 26 outside the carcass layer 18 as a whole.

  In the present invention, a cylindrical side tread may be formed on the outer side of the carcass layer on the first forming drum by a ribbon lamination method, and then the carcass layer and the side tread may be deformed into a substantially toroidal shape. In addition, a substantially saddle-shaped side tread is formed on the surface of the rotating disk using a ribbon lamination method, and the formed side tread is pasted on both outer sides in the axial direction of the carcass layer bulging and deformed in a substantially toroidal shape. Further, a rigid core may be used in place of the forming drum, and a side tread may be formed by ribbon lamination on the outside of the carcass layer formed on the rigid core.

  Next, after forming the belt layer 20 (belt ply 21) on the radially outer side of the carcass layer 18 and the side tread 26 (here, the radially outer end of the side tread 26) by the above-described constant width strip method. The outer chafer 45 is formed on the outer side in the axial direction of the filler 27 by the ribbon laminating method, and the rubber chafer 33 is constituted by the inner chafer 36 described above, and the radially outer portion of the side tread 26 and the belt A top tread 22 is formed on the radially outer side of the layer 20 by the ribbon laminating method to obtain a green tire 47.

  Here, as described above, when the side tread 26 is formed by winding the rubber strip 46 while shifting in the width direction, the outer surface of the side tread 26 is substantially circumferentially formed by the adjacent rubber strips 46 overlapping each other. However, since the rubber strip 46 is wound many times as described above, a large number of V grooves 60 are also formed (see FIG. 5). If such a V-groove 60 remains in the pneumatic tire 11, stress concentration due to the bending of the sidewall portion 14 is repeated at the groove bottom portion 61 of the V-groove 60 when the tire 11 is loaded and rolled. As a result, cracks are likely to occur on the outer surface of the side tread 26 (groove bottom 61 of the V-groove 60).

  For this reason, in this embodiment, a sheet-like member 56 made of unvulcanized rubber that has been heated by a heating machine is supplied and pressure-bonded to the outer surface of the side tread 26. Here, the rubber constituting the sheet-like member 56 supplied to the outer surface of the side tread 26 is heated to a high temperature and the viscosity is considerably lower than that at normal temperature. As a result, it can easily flow into the entire region of the V-groove 60 and can be filled.

  As a result, the V-groove 60 is completely filled up with the rubber of the sheet-like member 56 up to the groove bottom 61 and disappears, and the outer surface of the portion is smoothed (see FIG. 6). As a result, even if the pneumatic tire 11 in which the V-groove 60 has disappeared is loaded and rolled, stress concentration due to the bending of the sidewall portion 14 does not occur repeatedly in the side tread 26 (V-groove 60). As a result, the occurrence of cracks on the outer surface of the side tread 26 can be strongly suppressed.

  Here, as the above-mentioned heating machine, for example, the one shown in FIGS. 3 and 4 can be used. In the figure, reference numeral 50 denotes a screw-type heating machine as supply pressure bonding means arranged on both outer sides in the axial direction of the green tire 47 (second molding drum 37). This heating machine 50 is not shown in the drawing. The green tire 47 can be approached and separated by the separating means. The heating machine 50 has a substantially cylindrical cylinder barrel 51, and a screw 52 that receives a driving force from a driving motor (not shown) and rotates is accommodated in the cylinder barrel 51.

  At the rear end of the cylinder barrel 51, a hopper 53 for guiding the unvulcanized rubber G in the form of a sheet or pellets is provided in the cylinder barrel 51, and the normal temperature supplied to the cylinder barrel 51 through the hopper 53 is reduced. The unvulcanized rubber G flows toward the tip while being heated by the rotation of the screw 52. At this time, the unvulcanized rubber G generates heat due to its own flow deformation, frictional resistance with the cylinder barrel 51 and the screw 52, and the temperature rises and the viscosity falls.

  Further, a head 54 is fixed to the tip of the cylinder barrel 51, and when the heating machine 50 approaches the green tire 47, the side of the green tire 47 (side tread 26) is fixed to the tip of the head 54. A die 55 that is slightly away from the outer surface of the die 55 is fixed. Then, the head 54 of the heating machine 50 is brought close to contact with the outer surface of the side tread 26 of the rotating green tire 47 by the contact / separation means, and then heated by the rotation of the screw 52 from the die 55. While the unvulcanized rubber G that has been put is pressed against the outer surface of the side tread 26, the sheet-like member 56 is extruded by one round length.

  At this time, the sheet-like member 56 is pressed against the outer surface of the side tread 26 by extrusion pressure and flows into the V-groove 60 to form the rubber coating layer 28 described above. In the present invention, a gear pump type heating machine or a heating roll is used as the supply pressure bonding means, or a radiant heat source for heating the sheet-like member by radiant heat and a pressure roller for pressure-bonding the heated sheet-like member are used. You may do it.

  Here, in the normal pneumatic tire 11, a position M that is separated from the bead heel 29 by 50% of the tire cross-section height H radially outward and a position N that is 75% of the tire cross-section height H separated radially outward. Since a large bend (surface strain) occurs in the region R between and due to load rolling, cracks are likely to occur in the groove bottom 61 of the V groove 60 located in the region R. For this reason, in order to effectively suppress the occurrence of such cracks, it is preferable to supply and pressure-bond the sheet-like member 56 (rubber coating layer 28) to at least the region R. Here, the width of the sheet-like member 56 is slightly larger than the length of the region R in the meridian direction.

  In particular, in the pneumatic tire 11 having an aspect ratio of 0.7 or less, a large surface distortion is generated on the outer surface of the region R. Therefore, the sheet-like member 56 is supplied and pressure-bonded to such a low-flat ratio pneumatic tire. It is preferable. Further, as described above, the cross-sectional shape of the sheet-like member 56 that is crimped to the side surface of the green tire 47 may be a shape that becomes thinner from the center in the width direction toward both outer ends in the width direction. If there is a step, no step is generated at both radially outer ends of the rubber coating layer 28.

  If the sheet-like member 56 is supplied and pressure-bonded to the entire outer surface of the side tread 26, all the V-grooves 60 formed on the outer surface of the side tread 26 disappear, and the generation of the cracks is more strongly suppressed. More preferably, in this case, the width of the sheet-like member 56 is substantially equal to the peripheral length of the peripheral surface of the side tread 26 in the meridian direction.

  In the present invention, the sheet-like member 56 may be supplied and pressure-bonded to the outer surfaces of the top tread 22 and the outer chafer 45 formed by the ribbon lamination method and covered with the rubber coating layer. When the tire constituent member formed by the ribbon laminating method is exposed on the outer surface of 47, a sheet-like member may be supplied to the exposed surface and covered with a rubber coating layer. At this time, it is preferable to use rubber of the same material for the rubber constituting the tire constituent member formed by the ribbon laminating method and the rubber constituting the rubber coating layer pressed against the outer surface of the tire constituent member.

  The above-described supply pressure bonding of the sheet-like member 56 is performed at any time as long as the side tread 26, the top tread 22, and the outer chafer 45 are formed by the ribbon laminating method and until vulcanization described later. May be. Further, when the sheet-like member 56 is supplied and pressed, if the entire region cannot be covered at once, the rubber coating layer is divided into a plurality of regions in the meridian direction, and the sheet-like member is supplied and pressed to each region. You may do it.

  Here, if the gauge of the sheet-like member 56 extruded from the heating machine 50 is less than 0.5 mm, the gauge of the sheet-like member 56 may be thinner than the depth of the V-groove 60. 56 cannot fill up to the groove bottom 61 of the V-groove 60, and a space may remain in the vicinity of the groove bottom 61. On the other hand, if the gauge exceeds 1.5 mm, the V-groove 60 formed by the sheet-like member 56 is Since the filling effect is saturated, the weight of the tire is unnecessarily increased. However, if the gauge of the sheet-like member 56 is within the above range, the V-groove 60 can be completely eliminated. It is preferable because it is possible to prevent an unnecessary increase in weight of the tire.

  The Mooney viscosity of the heated rubber constituting the sheet-like member 56 is preferably in the range of 40 to 70. The reason is that when the Mooney viscosity is less than 40, it becomes difficult for the sheet-like member 56 to maintain its shape, whereas when the Mooney viscosity exceeds 70, the sheet shape on the outer surface of the side tread 26 is When the member 56 is crimped, it becomes difficult for the sheet-like member 56 to flow to the groove bottom 61 of the V-groove 60, and there is a possibility that a space may remain in the vicinity of the groove bottom 61. This is because the sheet-like member 56 can be easily made to flow to the groove bottom 61 of the V-groove 60 by the pressure bonding while maintaining the desired shape. Here, Mooney viscosity is a value of ML1 + 4 (100 degrees C), and is a viscosity of rubber measured in accordance with JIS K6300.

  Next, after the green tire 47 having the side tread 26 whose outer surface is covered with the rubber coating layer 28 as described above is taken out from the second molding drum 37, a known tire vulcanization mold (not shown) is included. Carry into the vulcanization means and vulcanize to make a vulcanized tire. At this time, the side tread 26 and the sheet-like member 56 are vulcanized and integrated.

    In the above-described embodiment, after the side tread 26 is formed, the belt layer 20 and the top tread 22 are formed. However, in the present invention, after the belt layer is formed, the side tread and the top tread are formed. These may be formed in the order, or in the order of the top tread and the side tread, or may be formed simultaneously.

  In the present invention, the belt tread band is formed in advance by a cylindrical drum different from the first and second forming drums, and the side tread is formed on the second forming drum. You may make it affix a band on the radial direction outer side of the carcass layer made into the substantially toroidal shape. Furthermore, in the present invention, the chafer, the inner liner, the carcass layer, the belt layer, and the top tread may be composed of a sheet-like long ply.

    Next, Test Example 1 will be described. In this test, a sheet-like member having a Mooney viscosity of 50, a gauge of 1.0 mm, and a width direction length substantially the same as the radial direction length of the outer surface of the side tread is circumferentially arranged on both outer sides in the axial direction of the side tread. It is the same as the implementation tire except that the implementation tire in which only the entire length of the side tread is covered with the rubber coating layer from the outside and the rubber coating layer covering the outer surface of the side tread are omitted by supplying and pressing one circumference along the circumference. A comparative tire having a structure was prepared. Here, the size of each of the tires described above was 265 / 70R16.

  Next, each tire is mounted on a 16 × 7J rim, filled with a low internal pressure of 100 kPa, then pressed against the drum while applying a load of 9.8 kN, and run at a speed of 60 km / h until the failure occurred. The travel distance was measured. As a result, in the comparative tire, cracks occurred from the V-grooves on the outer surface of the side tread when traveling 5000 km. On the other hand, in the case of running tires, cord breakage occurred at the time of traveling 8000 km, but no cracks occurred on the outer surface of the side tread.

  The present invention can be applied to the industrial field of pneumatic tires.

It is a meridian half section view of a pneumatic tire showing Embodiment 1 of the present invention. FIG. 3 is a front sectional view showing the manufacturing process of the first embodiment. FIG. 3 is a front sectional view showing the manufacturing process of the first embodiment. FIG. 4 is a cross-sectional view taken along the line II of FIG. It is the A section expanded sectional view of FIG. FIG. 4 is an enlarged cross-sectional view of a B part in FIG. 3.

Explanation of symbols

11 ... Pneumatic tire 18 ... Carcass layer
26… Side tread 29… Bead heel
46… Rubber strip 47… Green tires
50 ... Supply pressure bonding means 56 ... Sheet-like member
60 ... V-groove H ... Tire cross-section height M, N ... Position

Claims (6)

    Forming a side tread by winding the rubber strip on the outer side of the carcass layer while being overlapped while shifting in the width direction, and an unvulcanized rubber heated on the outer surface of the side tread Manufacturing a pneumatic tire comprising: a step of supplying and pressing a sheet-like member to fill a V-groove formed by an adjacent rubber strip; and a step of vulcanizing the green tire having the side tread. Method.     The sheet-like member is supplied at least between a position M spaced radially outward from the bead heel by 50% of the tire cross-section height H and a position N spaced radially outward by 75% of the tire cross-section height H. The method for producing a pneumatic tire according to claim 1, wherein the pneumatic tire is crimped.     The method for manufacturing a pneumatic tire according to claim 1 or 2, wherein a gauge of the sheet-like member is in a range of 0.5 to 1.5 mm.     The method for producing a pneumatic tire according to any one of claims 1 to 3, wherein the Mooney viscosity of the hot rubber constituting the sheet-like member is within a range of 40 to 70.     Side tread forming means for forming a side tread by winding the rubber strip on the outside of the carcass layer while shifting the rubber strip in the width direction, and unvulcanized rubber heated on the outer surface of the side tread Characterized in that it comprises supply pressure bonding means for supplying and pressure-bonding a sheet-like member made of the above and filling a V groove formed by an adjacent rubber strip, and vulcanizing means for vulcanizing the green tire having the side tread. Pneumatic tire manufacturing equipment.     A pneumatic tire manufactured using the method for manufacturing a pneumatic tire according to claim 1.

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