The present invention relates to a belt drum device used for manufacturing a pneumatic tire capable of having improved high-speed durability performance.
Conventionally, in a process of forming a green tire (tire before vulcanization) for a pneumatic tire, the following method has been known. Specifically, as shown in
Further, at this time, a green tire main body (f) is formed by being inflated to have a toroidal shape on a shaping drum (c) positioned adjacently to the belt drum device (a), for example. In the method of forming the green tire main body (f), first, a sheet-like carcass ply (d) is wound in a cylindrical shape on a carcass forming drum (not shown), second, bead cores (e) are attached to both edges of the wound carcass ply to form a carcass base body, then a cylindrical green tire main body (f1) including the carcass base body is formed. Next, by using the shaping drum (c), the green tire main body (f1) is inflated to form the toroidal green tire main body (f). Next, as shown in
However, in this stitch process, an outer diameter of the belt structure (b) is remarkably decreased at both edges thereof, resulting in a so-called minus stretch, which leads to undulating deformation, therefore, meandering and arrangement disorder occur in belt cords (not shown) of the belt plies (b1). In particular, if a band ply (not shown) is included in the belt structure (b), since the band cords are continuous in the circumferential direction, meandering becomes large. As described above, it is possible that tires manufactured by the conventional manufacturing method cannot exert high high-speed durability performance for the reasons described above. In order to solve such a problem, for the purpose of suppressing the undulating deformation in the stitch process, it is required that the belt plies (b1) of the belt structure (b) have a shape close to a profile of the belt of the tire after vulcanization in advance of the stitch process.
Japanese Unexamined Patent Application Publication No. 2014-226813 has disclosed a belt drum device for solving the above problem. For example, as shown in
In the belt drum device (h) configured as described above, the outer peripheral surface (h1) can be secured in parallel with the drum rotational axis (i1) of the drum base (i) in a contracted state. Further, as shown in
However, each of the central portion (j1) and the side portions (j2) of the belt drum device (h) is formed in a substantially rectangular shape in a transverse cross-sectional view thereof, thus, in the expanded state, the outer peripheral surface (h1) is formed by a combination of three straight lines, therefore, angular protruding portions (n) are formed at connecting portions between the central portion (j1) and the side portions (j2), thereby, it is difficult to form the belt plies (b1) in a smooth circular arc shape.
The present invention was made in view of the above, and a primary object thereof is to provide a belt drum device used for manufacturing a pneumatic tire having excellent high-speed durability performance by improving the outer peripheral surface of the belt drum device.
In one aspect of the present invention, a belt drum device for forming a belt structure including a belt to be used in a tread of a tire comprises a drum base rotatable around a drum rotational axis, a plurality of belt support portions arranged outside the drum base around the drum rotational axis in a drum circumferential direction, and a plurality of expansion and contraction means each for expanding and contracting corresponding one of the belt support portions in a drum radial direction, wherein each of the plurality of the belt support portions comprises a first link plate of which outer end is rotatably connected with a first end of the drum base, a second link plate of which outer end is rotatably connected with a second end of the drum base, and
a pin connecting inner ends of the first link plate and the second link plate so as to be movable in the expanding and contracting direction, each of the first link plate and the second link plate has an outer peripheral surface around which the belt is wound in the drum circumferential direction, in a transverse cross-sectional view passing through the drum rotational axis of the first link plate and the second link plate in a contracted state, each of the outer peripheral surfaces comprises a flat surface portion extending straight on a side of the outer end in a drum axial direction and an arc-shaped curved surface portion connected with the flat surface portion and curved toward the drum rotational axis as it approaches the inner end, and in a transverse cross-sectional view passing through the drum rotational axis of the first link plate and the second link plate in a expanded state, the curved surface portion of the first link plate and the curved surface portion of the second link plate are substantially continuous so as to form a continuous arc region convex outwardly in the drum radial direction.
In another aspect of the invention, it is preferred that the continuous arc region in the expanded state has a width in a range of from 30% to 85% of a width of the outer peripheral surface.
In another aspect of the invention, it is preferred that a radius of curvature of the curved surface portion is in a range of from 260 to 1200 mm.
In another aspect of the invention, it is preferred that in the contracted state, a maximum concave amount of the curved surface portion with respect to the flat surface portion is not more than 10 mm.
In another aspect of the invention, it is preferred that the outer ends of the first link plate and the second link plate are each provided with an elongated hole elongated in a longitudinal direction of the first link plate and the second link plate, the first link plate and the second link plate are connected with the drum base by the pin positioned inside the elongated holes so as to penetrate both of the elongated holes so that the first link plate and the second link plate can also slide with respect to the drum base, and the inner ends of the first link plate and the second link plate are connected with each other so as not to slide with respect to each other.
An embodiment of the present invention will now be described in conjunction with accompanying drawings.
The belt structure 32 is composed of the belt 37, the band 38, and the tread rubber 39, for example. The belt structure 32 formed by the device 1 is applied on a green tire main body (not shown), which includes the carcass 36, waiting on a downstream side in the process to form a green tire.
The drum base 2 in this embodiment is formed in a cylindrical shape and includes a drum main body 2A having an outer circumferential surface portion (2a) extending in a drum circumferential direction, and a drum rotational shaft portion 2B projecting outward from a side surface (2b) on one side of the drum main body 2A.
The drum rotational shaft portion 2B of the drum base 2 in this embodiment is supported in a cantilever manner by a drive unit (T) in which an electric motor (not shown) for rotating the drum rotational shaft portion 2B, a gear case (not shown), and the like are stored.
In this embodiment, a plurality, specifically in about a range from 30 to 50, of the belt support portions 3 is arranged on the outer circumferential surface portion (2a) of the drum base 2 around the drum rotational axis (2c) in the drum circumferential direction. Each of the belt support portions 3 in this embodiment includes a first link plate 5, a second link plate 6, and a pin 7.
The first link plate 5 and the second link plate 6 in this embodiment are configured in the same manner. Thereby, the first link plate 5 will be described on behalf of both of them.
The first link plate 5 in this embodiment includes a link main body portion 8 formed in a substantially prismatic column shape and extending along a drum axial direction of the drum base 2, and a rotatably holding portion 9 for holding the link main body portion 8 in a rotatable manner.
The link main body portion 8 has an inner peripheral surface 10 that faces the drum base 2 and an outer peripheral surface 11 that is opposite to the inner peripheral surface 10 and around which the belt 37 is wound.
The outer peripheral surface 11 of the link main body portion 8 in this embodiment has a second flat surface portion 16 extending straight in the drum axial direction on a side of the outer end (5e), and an arc-shaped first curved surface portion 17 connected with the second flat surface portion 16 and curved toward the drum rotational axis (2c) as it approaches the inner end (5i). The first curved surface portion 17 and the first flat surface portion 13 in this embodiment are connected with each other in a smooth circular arc shape.
The link main body portion 8 in this embodiment is provided with an elongated hole (8a) elongated in a longitudinal direction of the link main body portion 8 and arranged on the side of the outer end (5e), and a circular hole (8b) arranged on the side of the inner end (5i).
The rotatably holding portion 9 includes a base 9A fixed to the outer circumferential surface portion (2a) of the drum base 2, and a holding base portion 9B protruding outwardly in the drum radial direction from the base 9A and provided with a first pin (9a) to be positioned inside the elongated hole (8a) so as to penetrate the elongated hole (8a). The first pin (9a) of the rotatably holding portion 9 is positioned inside the elongated hole (8a) of the link main body portion 8 so as to penetrate the elongated hole (8a), thus, the link main body portion 8 is rotatably held by the first pin (9a), therefore, it is possible that the link main body portion 8 rotates around the first pin (9a) while sliding along the drum axial direction.
The pin 7 in this embodiment is positioned inside the circular hole (8b) of the first link plate 5 and the circular hole (8b) of the second link plate 6 so as to penetrate both of the circular holes (8b), therefore, the first link plate 5 and the second link plate 6 can rotate around the pin 7 without sliding in the drum axial direction.
As shown in
In the device 1 configured as such, the expansion and contraction of the piston rod (21a) of the expansion and contraction means 4 moves the inner end (5i) of first link plate 5 and the inner end (6i) of the second link plate 6 inwardly and outwardly in the drum radial direction while making the outer end (5e) of the first link plate 5 and the outer end (6e) of the second link plate 6 slide in the drum axial direction. Thereby, the outer peripheral surfaces 11 of the first link plates 5 and the second link plates 6 define the contracted state 51 and the expanded state 52.
Further, the first inclined portion 14 is inclined, therefore, contact of the first link plate 5 with the outer circumferential surface portion (2a) of the drum base 2 and with the base 9A when the first link plate 5 slides and rotates is suppressed.
Next, a method of manufacturing the belt structure 32 by using the device 1 in this embodiment will be described. The belt structure 32 in this embodiment is formed by sequentially arranging the belt ply 37A, the band ply 38A, and the tread rubber 39 from the inside to the outside in the tire radial direction in this order.
As shown in
Next, as shown in
The curved surface portion 22 concave toward the drum rotational axis (2c) is formed in the outer peripheral surface 11 in this embodiment, therefore, it is preferred that both edges in the drum axial direction of the belt ply 37A are held by a vacuum absorption device or a magnet, for example. From this point of view, in the contracted state 51, it is preferred that a maximum concave amount D1 of the first curved surface portion 17 with respect to the second flat surface portion 16, that is, a distance in the drum radial direction of the curved surface portion 22 is not more than 10 mm. If the maximum concave amount D1 is more than 10 mm, the both edges of the belt ply 37A can not be held by the above-described vacuum absorption device or the like, therefore, it is possible that accurate formation can not be performed.
Next, each of the belt support portions 3 is expanded in the drum radial direction by the expanding and contraction means 4. Specifically, as shown in
In order to effectively exert the effects described above, as shown in
It is preferred that a radius of curvature (R) (shown in
It is preferred that both edges of the belt ply 37A are kept held by the above-mentioned vacuum absorption device or the like when the belt support portions 3 are expanded.
Next, in the expanded state 52, the band ply 38A and the tread rubber 39 (not shown) are wound in turn around the outside in the drum radial direction of the belt ply 37A. Thereby, the belt structure 32 is formed. The band ply 38A and the tread rubber 39 may be sheet-like or may be formed by spirally winding a strip having a width in about a range of from 10 to 30 mm in the drum axial direction.
While detailed description has been made of an especially preferred embodiment of the present invention, the present invention can be embodied in various forms without being limited to the illustrated embodiment.
Number | Date | Country | Kind |
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2017-055694 | Mar 2017 | JP | national |
Number | Name | Date | Kind |
---|---|---|---|
3184361 | Allitt | May 1965 | A |
3485692 | Frazier | Dec 1969 | A |
3607558 | Nebout | Sep 1971 | A |
3718520 | Leblond | Feb 1973 | A |
4220494 | Kawaida | Sep 1980 | A |
8899292 | Jones | Dec 2014 | B2 |
20140338818 | Otani | Nov 2014 | A1 |
Number | Date | Country |
---|---|---|
1510912 | Jan 1968 | FR |
1287805 | Sep 1972 | GB |
2014-226813 | Dec 2014 | JP |
616151 | Jul 1978 | SU |
Number | Date | Country | |
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20180272642 A1 | Sep 2018 | US |