Method of producing tire reinforcing member

Abstract: The method comprises causing cords (1) to pass through respective small apertures of a guide plate (3) to arrange them in a predetermined positional relation, passing the cords over winding type braking means (4), and diverting the cords about a dancer roller (8). Thereafter, the cords are caused to pass through respective small apertures of a movable guide plate (11) which is reciprocated moved in horizontal directions perpendicular to the advancing direction of the cords so that the cords are reciprocatively supplied to a calender (12) for rubber coating, provided closely adjacent the movable guide plate (11), to sandwich the cords in the form of waves betwen rubber sheets (20) and coat the cords by the rubber sheets, thereby obtaining the reinforcing member (21). Shapes of the waves of the cords can be modified by changing traverse distances of the movable guide plate (11) and relative speeds between rotating speed of the calender (12) and reciprocation speed of the movable guide plate (11).

Description: This invention relates to a method of producing reinforcing members to be used in tires and having elongations which do not detrimentally affect tire performance and enable stresses to be uniformly distributed in width directions without any stress concentration. Rubber members having cords embedded therein have been widely used as elastic members having cut-resistant property in various fields. When such elastic members are used in structures subjected to various external forces such as tires, in addition to the cut-resistant property they are required to have elongations to an extent such that they do not affect the tire performance. From this viewpoint, there have been elastic members realizing suitable elongations with the aid of wave-shaped cords embedded therein, and various kinds of methods of producing such elastic members have been proposed. A few of the methods will be explained herein referring to Figs. 1-3. A first example is a spiral stripe method disclosed in Japanese Patent Application Laid-open No. 47-13,684. As shown in Fig. 1, stripes 01 are embraced between rubber-like elastic members 02 and 03 and embedded therein. On the way of supplying the stripes, they are caused to pass through a fixed pattern plate 05 and working pattern plates 04 moved along orbits of circular arcs, so that the stripes 01 are permanently spirally set or deformed. After the deformed stripes 01 have passed through a guide unit 06, they are pressed between rubber-like elastic members 02 and 03 by means of upper and lower pressure guide rollers 07 and 08 to form a rubber-like reinforced elastic structure having wave-shaped stripes embedded therein. As second example shown in Fig. 2 is a gear setting method disclosed in Japanese Patent Application Laid-open No. 52-91,967. One fiber web 012 is transferred in its longitudinal direction by a chain conveyor 017. A plurality of fiber yarns 011 are supplied onto an upper surface of the chain conveyor 017 with substantially equal intervals in its width directions. In order to supply the fiber yarns, a pair of gear-shaped rollers 014 and 015 are used, which are formed on their outer circumferences with a plurality of crests and valleys. Fiber stripes 011 are supplied from a creel 010 and passed through the rollers 014 and 015 immediately before they arrive onto the upper surface of the web 012 so that the stripes 011 are shaped into wave-forms with substantially equal pitches in their lengthwise direction. At a location where the fiber web 012 supporting the plurality of the wave-shaped fiber stripes 011 has been somewhat transferred in the longitudinal direction, another fiber web 013 is supplied onto the fiber stripes 011. The assembled stripes and webs are then subjected to needle-punching by means of needling means 016 to obtain an unwoven cloth 018. A third example shown in Fig. 3 is a zigzag belt method disclosed in Japanese Patent Application Laid-open No. 61-502,877. A flexible endless belt 022 extends about cylindrical members 020 and 021. Coated continuous cord reinforcing stripes 023 in the form of waves are shaped in wave-forms on the endless belt 022. In more detail, the continuous cord reinforcing stripes 023 are supplied through suitably shaped grooves in matching means 024 and between rollers 025 and 026 rotating in opposite directions and forcing the stripes 023 against the endless belt 022. The matching means 024 is connected through control belts 028 to a support 027 reciprocatively driven by means of a cylindrical cam device 026. The cord reinforcing stripes 023 are thus supplied onto the endless belt 022 in the zigzag patterns over the width of the endless belt 022. Among the above three examples, in the spiral stripe method and the gear setting method of the first and second examples, stripes susceptible to plastic deformation such as steel cords can be easily permanently set into wave-forms. However, these methods could not be used for soft cords such as chemical fibers because they are difficult to be permanently set. Moreover, it is difficult to make uniform pitches and intervals of the waves of cords. Unevenness in wave in width directions and overlaps of cords often occur which would cause stress concentration and in many cases detrimentally affect life of tires. Further, modification in wave-form could not be easily carried out so that these methods could not meet various needs. In the case of cords being overlapped, thicknesses of formed reinforcing members become uneven so that tire performance is detrimentally affected. Moreover, air is accumulated in the overlapped portions of cords. In the worst cases, the accumulated air may cause separation of reinforcing members. In the zigzag belt method of the third example, the coated cord reinforcing stripes are used so that an apparatus for coating the cords is needed. In the method, such coated cords are arranged one upon the other so that the air is likely to be accumulated between the cords. In the zigzag belt method, moreover, the number of the coated cords arranged on the endless belt during one operation cycle is so limited that production efficiency remains at low value. It is an object of the present invention to provide an improved method of producing tire reinforcing members, which eliminates the disadvantage of the prior art and which is able to use high strength chemical fibers such as Kevlar and to easily change wave forms of cords to be embedded in reinforcing members and which is carried out by the use of a comparatively simple apparatus. The present invention provides a method of producing a tire reinforcing member comprising the steps of paying off chemical fiber cords from bobbins to pass through respective small apertures of a guide plate to arrange them in a predetermined positional relation, passing the cords over winding type braking means including winding rolls each having an outer surface coated with rubber, diverting the cords about a dancer roller, causing the cords to pass in parallel through respective small apertures of a movable guide plate reciprocated in horizontal directions perpendicular to the advancing direction of the cords, feeding the cords reciprocatively moved by the movable guide plate to pressing rolls of a calender for rubber coating, provided closely adjacent the movable guide plate, sandwiching the cords in the form of waves without overlapping the cords between two rubber sheets, and pressing the rubber sheets to each other to embed the cords into the rubber sheets and adhere closed surfaces of the rubber sheets to be integrated, thereby obtaining the tire reinforcing member. With the above method, cords snugly arranged by the guide plates are fed through the winding type braking means and the dancer roller and caused to pass through the small apertures of the movable guide plate. Therefore, the cords upstream of the movable guide plate are maintained under a predetermined tensile force with the aid of the winding type braking means. Moreover, any slack in the cords caused by the reciprocative movements of the movable guide plate is taken up by the dancer roller so that cords are uniformly moved together under the uniform tensile force to the movable guide plate. Therefore, the cords are always stably supplied in this manner. The cords passed through the movable plate are fed to the calender for rubber coating arranged closely adjacent the movable guide plate. Accordingly, the respective cords are under the predetermined tensile force and sandwiched between and coated with the rubber sheets, while forming wave-forms. Therefore, the method according to the invention is applicable to chemical fiber cords not susceptible to plastic deformation. Shapes of the wave-forms of the cords are readily modified by changing traverse distances of the movable guide plate and relative speeds between rotating speed of the calender and reciprocative moving speed of the movable guide plate. The invention will be further described, by way of example only, with reference to the accompanying drawings, in which: Figs. 1 - 3 are drawings for explaining methods of producing reinforcing members of the prior art; Fig. 4 is a schematic plan view of an apparatus to be used for carrying out one embodiment of the method according to the invention; Fig. 5 is a side view of the apparatus shown in Fig. 4; Fig. 6 is a side view illustrating driving means for a movable guide plate of the apparatus shown in Fig. 5; Fig. 7 is a drawing viewed in a direction shown by an arrow VII in Fig. 6; Fig. 8 is a partially removed drawing viewed in a direction shown in an arrow VIII in Fig. 6; and Fig. 9 is a partially removed plan view illustrating driving means for the movable guide plate. One embodiment of the invention is shown in Figs. 4-9. Fig. 4 is a plan view of an apparatus to be used for carrying out the method according to the invention and Fig. 5 is a side view thereof. A plurality of bobbins 2 are arranged upstream (left side viewed in Fig. 4 or 5) of proceeding lines of cords 1 wound about the bobbins 2. The cords are Kevlar cords of high strength chemical fibers. Kevlar is a high strength chemical fiber which is soft but does not undergo plastic-deformation and exhibits very small elongation when being subjected to a load. The cords 1 paid off the bobbins 2 are drawn to a guide plate 3 and pass through a plurality of small apertures formed at predetermined positions of the guide plate 3. The cords 1 passed through the guide plate 3 are then wound about winding rolls 5 and 6 of a winding type braking means 4. The winding rolls 5 and 6 are so constructed that the cords 1 extend about the upstream winding roll 5 over approximately a quarter of a circumference of the roll 5 in a clockwise direction and then extend about the downstream winding roll 6 over approximately a quarter of a circumference of the roll 6 in a counterclockwise direction and are fed to a next station. The cords 1 are retained in a predetermined positional relation between them by means of the guide plate 3 so that the cords 1 are snugly arranged in the same plane in parallel with each other with equal intervals when the cords extend about the winding roll 5. When the winding rolls 5 and 6 are being rotated, these rolls 5 and 6 are always subjected to braking action which will obstruct the rotation of the rolls 5 and 6. Therefore, the cords which are being pulled toward the downstream side are given constant tensile forces. The winding rolls 5 and 6 have large diameters and have large friction because their surfaces are coated with rubber. Therefore, lengths of the cords contacting the rolls are relatively long and coefficients of friction are comparatively large. As a result, the cords 1 are prevented from slipping so that tensile forces in the cords on the downstream side can be sufficiently maintained. After passing the winding roll 6, the cords 1 extend about a fixed roller 7 from above in the clockwise direction. Thereafter, the cords 1 extend about a dancer roller 8 over a lower half of its circumference in the counterclockwise direction and further extend about a fixed roller 9 downstream of the dancer roller 8 in the clockwise direction. In this case, the dancer roller 8 is hung between the fixed rollers 7 and 9. Therefore, the cords 1 are always forced downward by the dancer roller 8 by its gravity, so that upward and downward movements of the dancer roller 8 take up slack in the cords 1. The cords 1 paid off the fixed roller 9 pass through small apertures of a guide plate 10 and then through small apertures of a movable guide plate 11, respectively. The movable guide plate 11 is reciprocatively movable in a horizontal direction perpendicular to moving directions of the cords 1 so that the cords 1 upstream of the movable guide plate 11 are moved in a horizontal plane. Slack in the cords 1 which may occur in such a horizontal swinging motion of the cords 1 is taken up by the dancer roller 8 as above described. A calender 12 is arranged downstream of the movable guide plate 11. The calender 12 comprises upper and lower pressing rolls 13 and 14, and a pair of upper and lower feeding rolls 15 and 16 for supplying rubber sheets 20 between the pressing rolls 13 and 14. The cords 1 are sandwiched between upper and lower rubber sheets 20 fed from the feeding rolls 15 and 16 and pressed with pressure uniform in width directions so that the upper and lower rubber sheets 20 are integrally attached to each other to complete a tire reinforcing member 21. In this case, the movable guide plate 11 and the pressing portions of the upper and lower pressing rolls 13 and 14 are so closely adjacent each other that the cords 1 snugly arranged in a horizontal plane by means of the movable guide plate 11 are sandwiched between the rubber sheets 20, while the snugly arranged state is maintained. Vibration of the cords 1 on the upstream side of the movable guide plate 11 which may be caused by the reciprocative movement of the movable guide plate 11 is prevented by the guide plate 10 upstream of the movable guide plate 11. The movable guide plate 11 is reciprocatively moved with a selected predetermined period. Driving means for the reciprocative movement of the movable guide plate 11 will be explained by referring to Figs. 6-9. A horizontal support frame 31 is supported by support columns 30. A rail 32 is provided extending in horizontal directions on an upper surface of the horizontal support frame 31 along its center. A slide member 33 is slidably fitted on the rail 32. A support plate 34 having an L-shaped cross-section is fixed to the slide member 33 with an inner surface of a horizontal web of the support plate 34 being fixed to the slide member 33. An upper portion of the movable guide plate 11 long in width direction is fixed to and hung from an outer surface of a vertical web of the support plate 34 being bent downward on the downstream side. The movable guide plate 11 is formed along its lower edge with a plurality of small apertures 11a arranged in a row which are located below a lower edge of the horizontal support frame 31. A horizontal base plate 36 extending toward the upstream side is provided on a bracket 35 supported on the horizontal support frame 31 on the left side viewed from the upstream side (Fig. 7). On the horizontal base plate 36 is provided a motor 37 having a driving shaft 37a extending toward the downstream side. A crank 38 is fitted on the driving shaft 37a of the motor 37 and formed with an elongate aperture 38a which is long in a centrifugal direction. On the other hand, a bearing member 39 is provided on the support plate 34 on a side near to the motor 37. One end of a connecting rod 40 is pivotally connected to the crank 38 and the other end is pivotally connected to the bearing member 39. At the pivotal end of the connecting rod 40 to the crank 38 is provided a bearing (not shown) whose outer race is fitted to the connecting rod 40 and whose inner race is fixed in the elongate aperture 38a of the crank 38 by means of a bolt 42 passing through the elongate aperture 38a and a nut 43 threadedly engaged with the bolt 42. The pivotal portion of the connecting rod 40 to the crank 38 is thus positionally adjustable to any position along the elongate aperture 38a in the centrifugal direction. The driving means for the movable guide plate 11 is constructed as above described. When the motor 37 is energized to rotate the crank 38, the movable guide plate 11 is reciprocatively moved together with the slide member 33 and the support plate 34 by means of the connecting rod 40 pivotally connected to the crank 38. The traverse distance of the movable guide plate 11 is simply changed by changing the pivotal position of the connecting rod 40 to the crank 38. The cords 1 leaving she movable guide plate 11 reciprocatively moved are sandwiched and pressed between the rubber sheets 20 supplied from above and below at the pressing position of the pressing rolls 13 and 14. As shown in Fig. 9, therefore, the cords 1 passed through the movable guide plate 11 are pulled at the pressing position of the pressing rolls 13 and 14 so that the cords 1 extend linearly in parallel with each other between the movable guide plate 11 and the pressing rolls 13 and 14. However, when the rubber sheets 20 are fed by the pressing rolls 13 and 14 in the cord advancing direction, the cords 1 are reciprocatively moved in the width directions of the rubber sheets 20 by the action of the movable guide plate 11. Therefore, positions of the cords 1 in the width directions at the pressing position are varied as a function of time, with the result that the cords 1 are shaped in wave-forms sandwiched by the rubber sheets 20 downstream of the pressing position. In this case, the movable guide plate 11 is so positioned immediately before the pressing position of the pressing rolls 13 and 14 for the rubber sheets 20 that the distance between the movable guide plate 11 and the pressing position is as short as possible to prevent any slack in the cords 1. Accordingly, it is possible to form uniform waves of the cords 1 embedded in the tire reinforcing member 21. If slack may tend to occur, it can be prevented by rotating the bobbins 2 in rewinding directions as the case may be. Amplitude of wave-forms of the cords 1 is determined by the traverse distance of the movable guide plate 11. Therefore, change in amplitude of the wave-forms can be accomplished by changing the pivotal positions of the connecting rod 40 to the crank 38. On the other hand, the wave length can be readily changed by changing relative speeds between the rotating speeds of the pressing rolls 13 and 14 and the crank 38. Therefore, the apparatus for carrying out the method according to the invention can provide reinforcing members having most suitably wave-shaped cords embedded therein for various kinds of tires only with the one apparatus. Accordingly, the method of the invention is superior in flexibility for meeting requirements in wide ranges. The wave-forms of the cords 1 embedded in tire reinforcing members 21 are regular in width directions and uniform in shape. Accordingly, limiting design of construction of the tire is acceptable so that light weight and inexpensive tires can be obtained. Moreover, the forming of the waves of cords according to the invention is effected under the same physical conditions over the entire width of the reinforcing member, so that stress concentration is prevented and the life span of the tire may also be prolonged. According to the invention, the forming of the waves of cords is accomplished by changing embracing positions between the pressing rolls 13 and 14 so that previous permanent set of the cords 1 is not needed. Therefore, it is possible to use chemical fibers such as Kevlar which are difficult to be deformed so that the tire can be made light in weight. In the invention, moreover, direct rubber coating of bare cords is possible. The wave-forms of the cords 1 are formed on the same horizontal plane without overlapping of the cords so that air does not accumulate at overlapping portions. Therefore, damage to a tire due to separation of rubber sheets is completely prevented, which is caused by accumulated air. Even in reinforcing members having many cords with very narrow intervals of the cords, the cords do not overlap with each other, and rubber certainly flows between the cords by increasing the pressing force to an extent so that direct contact of the cords is prevented. Moreover, production efficiency can be raised by adopting four-calenders and the like having functions of long bobbins and rubber sheets. In view of installation, the production efficiency is high relative to investment in installation, thereby enabling cost of tire to be lowered. As can be seen from the above explanation, according to the invention, chemical fibers such as Kevlar which do not do plastic deformation can be used and therefore obtain light weight tires. As the embedded cords are shaped into wave-forms regular in width directions and uniform in wave-form, uniform reinforcing members are obtained in which stresses are distributed uniformly in width directions. Therefore, safety in tire construction design is improved and life of tire can be prolonged. Moreover, rigidities of wave-formed cords and rubber sheets can be properly set according to the invention so that improvement of various performances of tires is expected. A plurality of cords are arranged in the same plane to be embedded in the rubber sheets without overlapping so that reinforcing members having uniform thicknesses are formed. Therefore, there are very few reinforcing members deviating from predetermined thicknesses and separation of rubber sheets due to accumulated air can be prevented. As an installation is relatively inexpensive, reduction of cost of tire production is expected.

Claims: A method of producing a tire reinforcing member comprising the steps of paying off chemical fiber cords (1) from bobbins (2) to pass through respective small apertures of a guide plate (3) to arrange them in a predetermined positional relation, passing the cords over winding type braking means (4) including winding rolls (5, 6) each having an outer surface coated with rubber, diverting the cords about a dancer roller (8), causing the cords to pass in parallel through respective small apertures (11a) of a movable guide plate (11) reciprocated in horizontal directions perpendicular to the advancing direction of the cords, feeding the cords reciprocatively moved by the movable guide plate (11) to pressing rolls (13, 14) of a calender (12) for rubber coating, provided closely adjacent the movable guide plate (11), sandwiching the cords in the form of waves without overlapping the cords between two rubber sheets (20), and pressing the rubber sheets to each other to embed the cords into the rubber sheets and adhere closed surfaces of the rubber sheets to be integrated, thereby obtaining the tire reinforcing member (21). A method as claimed in claim 1, wherein the dancer roller (8) is suspended by the cords (1) from a pair of fixed rollers (7, 9) arranged upstream and downstream of the dancer roller (8) to force the cords downward by the weight of the dancer roller, thereby taking up slack in the cords. A method as claimed in claim 1 or 2, wherein the calender (12) comprises upper and lower pressing rolls (13, 14) and a pair of upper and lower feeding rolls (15, 16) for supplying the rubber sheets (20) between the pressing rolls (13, 14), the cords (1) being fed between the rubber sheets (20) fed from the upper and lower feeding rolls (15, 16). A method as claimed in any preceding claim, wherein amplitudes of waves of the cords are modified by changing a traverse distance of the movable guide plate (11). A method as claimed in any preceding claim, wherein lengths of waves of the cords are modified by changing relative speeds between rotating speed of the calender (12) and reciprocation speed of the movable guide plate (11).

Inventors: IKEDA KAZUNARI, IKEDA, KAZUNARI
Applicants: BRIDGESTONE CORP, BRIDGESTONE CORPORATION
Application year: 1989
Main classification: B29D30
IPC codes: B29D30, B32B37, B29C70, B32B25, B29K105, B29K21