Patent Publication Number: US-2005116374-A1

Title: Thin rubber member producing method, rubber rolling device and rubber rolling method

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to a method of manufacturing a thin rubber member, a rubber roller for forming an elongated rubber strip which is suitably designed for use in the method of manufacturing a thin rubber, and more particularly, to a method of rolling a rubber for forming the elongated rubber strip that is suitably designed for use in the method of manufacturing a thin rubber.  
      2. Background Art  
      Conventionally, a rubber member used for a tire, for example, a rubber sheet such as an inner liner or the like has been manufactured by a method of sheeting a rubber member by a so-called 2-roller die  300  as shown in  FIG. 20 , a method of sheeting a rubber sheet by a so-called 1-roller die  2  as shown in  FIG. 21 , or a method using four calendar rolls (not shown).  
      As for an inner liner  303  formed by such conventional methods as described above, the inner liner  303  during sheeting has a width W that corresponds to a distance between one bead toe and the other bead toe, along a tire inner surface as seen from a cross section along a tire rotational axis. After the extruded with this width, the inner liner  303  was cut to a length that corresponds to a circumferential length of the tire inner surface.  
      Further, it is desired that both end portions in a transverse direction of the inner liner  303  be tapered in order to prevent air or inner surface solutions from entering the inner liner  303 . As shown in  FIG. 20 , the both end portions are diagonally cut by the cutters  304 , or as shown in  FIG. 21 , the shape of a cap  306  is determined such that each of the both end portions of the inner liner  303  is tapered.  
      During a manufacturing process of a tire, a sheet of the inner liner  303  thus obtained is wound around a drum, and thereafter, tire structural members such as a carcass ply and the like are sequentially wound around the drum to thereby form a green tire.  
      If the inner liner  303  is manufactured by this method, a plurality of roller dies having different widths must be prepared in accordance with a size or a type of a tire, whereby a plant and equipment cost at a factory was high.  
      Thus, in recent years, a method in which a ribbon-shaped unvulcanized rubber strip is spirally wound around a drum to form a desired rubber sheet on the drum has been proposed (Japanese Patent Applications (JP-A) Laid-Open No. 2000-246812 or the like).  
      In a conventional method, when the ribbon-shaped rubber strip is wound around a drum such that portions in the vicinities of transverse direction end surfaces of the ribbon-shaped rubber strip are overlapped with one another so as not to form gaps between windings of a spiral. Therefore, level differences are formed on the surface of the rubber sheet thus formed, air is easily accumulated into concave portions of the level differences, and there has been a concern about a treatment of end portions of the rubber sheet.  
      Therefore, the inventors conducted various experiments and arrived upon a method of effectively manufacturing a thin rubber member which is optimal for inner liners or the like, in which level differences are not formed, and which can accommodate various sizes, by forming an elongated rubber strip in which taper portions are provided at both end portions in a transverse direction and by overlapping the taper portions one another.  
      In a case in which a rolled rubber sheet (rubber strip) having a predetermined width is sequentially formed with high accuracy, in prior art, as shown in  FIG. 22 , only a required configuration portion  402  is cut from the rolled rubber sheet fed out from a calendar roll  401  in the end, and remaining portions  403  are returned to an extruder or the like as a knead-back rubber and are subjected to a knead-back.  
      Change in a discharge amount of an unvulcanized rubber with respect to the calendar roll affects a width of the rolled rubber sheet that is supposed to be molded, and a width variation thereby occurs. Especially when both edge portions of the rolled rubber sheet to be molded are provided with inclining taper portions, it becomes difficult to obtain a width with high accuracy. For this reason, the rolled rubber sheet fed out from the calendar rolls  401  is cut into a required configuration so that the remaining rubbers  403  are provided for a knead-back.  
      The smaller (the more acute) the inclination angle of the taper portion of the rolled rubber sheet in order to improve a quality, the more difficult the increase of the width accuracy, thus making it more necessary to precisely cut the rolled rubber sheet into a required configuration.  
      To precisely cut the rolled rubber sheet into a required configuration by using the calendar roll  401  leads to a requirement of a knead-back operation for providing the remaining portion  403  for a knead back. Accordingly, it becomes disadvantageous in respect of space, troubles may easily occur, and there is also a concern that productivity may be inhibited.  
      Further, to repeat a knead-back of rubber leads to a change of rubber properties. This is the last operation to be carried out in order to stabilize the quality of the product.  
      There is provided a method in which a rolled rubber sheet is formed with high width accuracy by using a 1-roller die  405  as shown in  FIG. 23 . The 1-roller die  405  is heavy, requires high manufacturing cost, and outputs a small amount of a leakage of rubber thus necessitating a periodical treatment.  
      If an elongated rolled rubber sheet  508 , which is formed into a cross-sectional configuration as shown in  FIG. 24 (D) whose end portions in the transverse direction are tapered so as to form a taper portion respectively at both end portions in the transverse direction of the elongated rolled rubber sheet  508 , is rolled by a roller head, there have been provided two methods, one in which a rubber bank is produced on a roller head and the other in which a rubber bank is produced on the roller head.  
      First, if a rubber bank is produced on a roller head, as shown in  FIG. 24  (A), a rubber bank  504  is formed on a roller head  502  disposed at a rubber discharge side of a rubber extruder  500 . Since a cap  506  of a rubber extruder  500  is used simply to supply a constant amount of rubber into the roller head  502 , the cap  506  is generally formed into a circular shape as shown in  FIG. 24  (B) or a rectangular shape as shown in  FIG. 24 (C).  
      Next, if a rubber bank is not produced on the roller head  502 , the opening of the cap  506  is formed into a rectangular shape substantially similar to a roller head profile.  
      With a conventional method of producing a rubber bank on a roller head, a bank amount increases or decreases due to a variation of an amount in which rubber is discharged from a rubber extruder. Especially when a bank amount increases, rubber is swollen out from the roller head profile (see  FIG. 25 . A reference numeral  508 A refers to a swollen-out portion), and the swollen-out portion  508 A is kept in close contact with the roller head  502 , and sometimes adhered to the rolled rubber sheet, and there is caused a problem in that foreign matters enter the rolled rubber sheet.  
      As shown in  FIG. 26 (A), if a rubber bank is not produced on the roller head  502 , a comparatively wide extruding rubber  510  having a cross-sectional configuration as shown in  FIG. 26 (B) is rolled from the cap  506  by the roller head  502 .  
      During the rolling, rolling directions at a straight portion at the center of the rubber sheet (a portion having a fixed thickness) and those at taper portions are different from each other (directions of arrows: rubber orientations) as shown in  FIG. 27 . As a result, a sheet-contracted amount generated after the rolling is taper portions&lt;straight portion. Accordingly, a phenomenon in which taper portions are corrugated with time, whereby a problem is caused in that sheet quality may deteriorate.  
      In other words, when a low quality elongated rubber strip is used, as a matter of course, it is difficult to obtain a high quality rubber strip.  
      In view of the aforementioned facts, an object of the present invention is to provide a method of manufacturing a thin rubber member which has a constant thickness and which can accommodate various sizes, and a rubber roller and a rubber rolling method which can sequentially provide an elongated rubber strip having excellent configuration accuracy and high quality that can be used for manufacturing the thin rubber member.  
     DISCLOSURE OF THE INVENTION  
      Claim  1  of the present invention is a method of manufacturing a thin rubber member, comprising a first step of forming a segmented rubber strip by cutting a long rectangular rubber strip, that has taper portions formed at both end portions thereof, to have a predetermined length so as to be inclined with respect to a normal line stood vertically on a sheet surface and a second step of connecting a plurality of the segmented rubber strips to each other in a transverse direction such that the taper portions at both end portions in a transverse direction of each of the segmented rubber strips are overlapped to each other.  
      Next, an operation and an effect of the method of manufacturing a thin rubber member according to claim  1  will be explained.  
      First, in the first step, since the rectangular rubber strip is cut so as to be inclined with respect to a normal line stood vertically on a sheet surface, the end portions of the elongated rubber strip in a longitudinal direction is formed into a tapered shape.  
      In the second step, the segmented rubber strips are connected to each other in a transverse direction with the taper portions at both end portions in a transverse direction of each of the segmented rubber strips overlapped to each other, and a thin rubber member which has a large area and all of which edge portions are tapered can be formed.  
      In accordance with the method of manufacturing a thin rubber member, thin rubber members having various sizes can be manufactured by changing a length of an elongated rubber strip, a number of connections, and the like. In addition, a thin rubber member having a fixed thickness can be manufactured by the taper portions overlapping each other.  
      Claim  2  of the present invention is a method of manufacturing a thin rubber member, comprising a first step of forming a segmented rubber strip by cutting a long rectangular rubber strip, that has taper portions formed at both end portions thereof, to have a predetermined length, a second step of connecting a plurality of the segmented rubber strips to each other in a transverse direction such that the taper portions at both end portions in a transverse direction of each of the segmented rubber strips are overlapped to each other thereby obtaining a rubber sheet, and a third step of cutting both end portions of the rubber sheet in a direction orthogonal to a direction in which the segmented rubber strips are connected to each other so as to be inclined with respect to a normal line stood vertically on a sheet surface.  
      Next, an operation and an effect of the method of manufacturing a thin rubber member according to claim  2  will be explained.  
      In the first step, since the segmented rubber strips are formed by cutting the long rectangular rubber strip to have a predetermined length, the segmented rubber strip has taper portions formed at both end portions thereof.  
      In the next second step, the segmented rubber strips are connected to each other in a transverse direction such that the taper portions at both end portions in a transverse direction of each of the segmented rubber strips are overlapped to each other thereby obtaining a rubber sheet.  
      In the next third step, both end portions of the rubber sheet, in a direction orthogonal to a direction in which the segmented rubber strips are connected to each other, are cut so as to be inclined with respect to a normal line stood vertically on a sheet surface.  
      Accordingly, a thin rubber member which has a large area and all of which edge portions can be obtained.  
      Claim  3  of the present invention is a method of manufacturing a thin rubber member comprising a first step of forming a long rectangular rubber strip having taper portions at both end portions in a transverse direction, and a second step of spirally winding the elongated rubber strip while overlapping the taper portions with each other.  
      Next, an operation and an effect of the method of manufacturing a thin rubber member according to claim  3  will be explained.  
      In the method of manufacturing a thin rubber member according to claim  3 , first, in the first step, a long rectangular rubber strip having taper portions at both end portions in a transverse direction is formed.  
      During the next second step, the elongated rubber strip having taper portions at both end portions in a transverse direction is spirally wound while the taper portions are overlapped with each other thereby to form a cylindrical thin rubber member.  
      Further, when the thin rubber member is used as a tire structural member, the cylindrical thin rubber member can be used unchanged.  
      For example, when a green tire is manufactured, an elongated rubber strip is spirally wound around an outer circumferential surface of a drum, and a cylindrical inner liner (thin rubber member) can be formed at the outer circumferential surface of the drum.  
      Then, tire structural members such as a bead ring, a carcass ply, a side wall rubber, a belt, a tread and the like can be attached to the drum on which the inner liner has been formed, and a green tire can be formed.  
      Claim  4  of the present invention is the method of manufacturing a thin rubber member according to claim  3 , further comprising cutting a wind-start portion and a wind-end portion of the rectangular rubber strip are respectively into a tapered shape whose width gradually becomes narrow.  
      Next, an operation and an effect of the method of manufacturing a thin rubber member according to claim  4  will be explained.  
      If the rectangular rubber strip, whose both end portions in a longitudinal direction are cut at a right angle with respect to the longitudinal direction, is spirally wound, step differences are formed at the end portions respectively at the wind-start side and at the wind-end side. In accordance with the method of manufacturing a thin rubber member according to claim  4 , since each of the wind-start portion and the wind-end portion of the elongated rubber strip is cut into a tapered shape whose width gradually becomes narrow, step differences are not formed at the respective end portions at the wind-start side and at the wind-end side.  
      Further, the end portion in a longitudinal direction of the elongated rubber strip can be cut into the tapered shape before and after the spirally winding of the elongated rubber strip.  
      Claim  5  of the present invention is the method of manufacturing a thin rubber member according to claim  3 , further comprising cutting at least one portion of a cylindrical thin rubber member that is obtained by spirally winding the elongated rubber strip in an axial direction thereby obtaining at least one rubber sheet.  
      Next, an operation and an effect of the method of manufacturing a thin rubber member according to claim  5  will be explained.  
      At least one portion of the cylindrical thin rubber member is cut along an axis and expanded thereby obtaining at least one rubber sheet.  
      Claim  6  of the present invention is a rubber roller for sequentially forming an elongated rubber strip that is applied to the method of manufacturing a thin rubber member according to claim  1 , comprising an extruder which extrudes an injected unvulcanized rubber from a cap to form the unvulcanized rubber into a flat-strip shape, a pair of rollers which further forms the flat strip-shaped unvulcanized rubber discharged from the cap into a predetermined flat long rectangular rubber strip, and then feeds, and a control means which controls at least one of the extruder and the pair of the rollers thereby to sequentially form the elongated rubber strip having a predetermined cross-sectional configuration.  
      Next, an operation and an effect of the method of manufacturing a thin rubber member according to claim  6  will be explained.  
      The width of the elongated rubber strip fed out from the pair of the rollers is influenced by the discharge amount of the unvulcanized rubber from the extruder and the number of rotations of the pair of the rollers.  
      The control means controls to maintain the number of the discharge amount of the unvulcanized rubber from the extruder and the number of rotations of the pair of the rollers constant. Further, the control means controls to prevent the pair of the rollers from generating a knead-back rubber.  
      Accordingly, the elongated rubber strip having a predetermined width can be molded and fed out with high accuracy and stability.  
      Since merely providing the control means suffices the present invention, more space is not required, and a conventional knead-back operation is also unnecessary. Accordingly, the rubber roller of the present invention is advantageous in respect of space because it has a simple structure and can be manufactured inexpensively. Consequently, there is hardly any problem and small chance that inhibit productivity.  
      Further, since a knead-back is not effected, rubber properties do not change, whereby rubber quality can be maintained high.  
      Claim  7  of the present invention is the rubber roller according to claim  6 , further comprising a width sensor which detects a width of an elongated rubber strip fed out from the pair of the rollers, wherein, in order to feed an elongated rubber strip having a predetermined width, the control means feedback-controls a driving of the extruder on the basis of a width of the elongated rubber strip detected by the width sensor.  
      Next, an operation and an effect of the rubber roller according to claim  7  will be explained.  
      In the rubber roller according to claim  7 , since the control means feedback-controls a driving of the extruder on the basis of the width of the elongated rubber strip detected by the width sensor, a knead-back rubber is not generated, and accordingly, an elongated rubber strip having a predetermined width can be molded with high accuracy and excellent stability, and fed out.  
      Since mere addition of the width sensor to the control means suffices, more space is not required.  
      Claim  8  of the present invention is the rubber roller according to claim  6 , further comprising, a metering discharge pump which is provided at the extruder and which feeds the unvulcanized rubber toward the cap; and a pressure sensor which detects a pressure of the unvulcanized rubber at an inlet of the metering discharge pump, characterized in that the control means feedback-controls a driving of the extruder on the basis of a pressure of an unvulcanized rubber detected by the pressure sensor, and properly maintains a pressure of an unvulcanized rubber.  
      Next, an operation and an effect of the rubber roller according to claim  8  will be explained.  
      In the rubber roller according to claim  8 , the control means feedback-controls a driving of the extruder, and maintains a pressure of the unvulcanized rubber, which is extruded from the extruder and reached to the inlet of the metering discharge pump, within a fixed range. Therefore, a proper discharge amount of the unvulcanized rubber from the metering discharge pump is retained thus making it easy to maintain a proper configuration of the elongated rubber strip fed out from the pair of the rollers.  
      Claim  9  of the present invention is the rubber roller according to claim  8 , further comprising a rectifier tube which is interposed between the metering discharge pump and the cap, whereby the unvulcanized rubber is evenly supplied into the cap which forms the unvulcanized rubber into a flat strip.  
      Next, an operation and an effect of the rubber roller according to claim  9  will be explained.  
      If a distance from the metering discharge pump to a head is short, uneven filling of an unvulcanized rubber into the head occurs. Accordingly, the rectifier tube is interposed between the metering discharge pump and the cap, and uneven filling of the unvulcanized rubber into the head can be prevented, whereby the unvulcanized rubber can be maintained properly and stabilized.  
      Claim  10  of the present invention is the rubber roller according to claim  6 , wherein the cap with an opening whose shape is similar to a cross section along a transverse direction of the elongated rubber strip, the pair of the rollers having a portion with a gap whose shape is similar to the shape of a cross section in a transverse direction of the elongated rubber strip, between the rollers, and the control means which controls at least one of an extruding amount per an hour of the unvulcanized rubber extruded by using the extruder, and a rotational speed of the pair of the rollers, so as not to form an unvulcanized rubber bank.  
      Next, an operation and an effect of the rubber roller according to claim  10  of the present invention will be explained.  
      First, in the first step, the unvulcanized rubber member is extruded from the cap of the extruder.  
      The shape of the opening of the cap is similar to a cross-section along a transverse direction of the elongated rubber strip having taper portions each of which has a thickness which gradually decreased toward the end portions in the transverse direction of the elongated rubber strip.  
      For this reason, a cross-section in a transverse direction of the unvulcanized rubber member extruded from the cap is similar to a cross-section along a transverse direction of the elongated rubber strip. Namely, the elongated rubber strip has taper portions each of which thickness gradually decreased toward the end portions in a transverse direction of the elongated rubber strip.  
      Next, the unvulcanized rubber member extruded from the cap is rolled in accordance with the rotation of the pair of the rollers.  
      During the rolling, in the same way, the unvulcanized rubber member extruded from the cap is rolled through the portion whose shape is also similar to a cross-section along a transverse direction of the elongated rubber strip.  
      Further, the control means controls at least one of an extruding amount per an hour of the unvulcanized rubber extruded by using the extruder, and a rotational speed of the pair of the rollers, so as not to form an unvulcanized rubber bank on the pair of the rollers.  
      Since a rubber bank is not formed on the pair of the rollers, neither unnecessary unvulcanized rubber nor foreign matters (unnecessary unvulcanized rubber peeled off from the roller surface) are deposited on a roller surface and on the elongated rubber strip, respectively.  
      Regarding the description of “a rubber bank is not formed on the pair of the rollers”, it includes an extremely small amount of rubber bank (which, for example, is caused by a rubber extruding amount or an error of the rotational number of the rollers) formed within a range which does not form corrugations at the taper portions of the resultant elongated rubber strip.  
      Claim  11  of the present invention is a method of rolling a rubber for sequentially forming an elongated rubber strip which is applied to the method of manufacturing a thin rubber member according to claim  1 , comprising a first step of, by using an extruder, extruding an unvulcanized rubber from a cap having an opening whose shape is similar to a cross-section along a transverse direction of the elongated rubber strip, and a second step comprising, during a rotation of the pair of the rollers, rolling the unvulcanized rubber extruded from the cap without forming a rubber bank at a portion with a gap whose cross-section is similar to a cross-section along a transverse direction of the elongated rubber strip formed between the rollers.  
      Next, an operation and an effect of the rubber roller according to claim  11  of the present invention will be explained.  
      First, in the first step, the unvulcanized rubber member is extruded from the cap of the extruder Since the shape of the opening of the cap is similar to a cross-section in the transverse direction of the elongated rubber strip in which taper portions are formed at both end portions of the elongated rubber strip and each of the taper portions has a thickness which gradually decreases toward the end portions in the transverse direction of the elongated rubber strip, a cross-section in a transverse direction of the unvulcanized rubber member extruded from the cap is similar to that of the elongated rubber strip. Namely, the elongated rubber strip has taper portions each of which thickness gradually decreased toward the end portions in a transverse direction of the elongated rubber strip.  
      Next, the unvulcanized rubber member extruded from the cap is rolled in accordance with the rotation of the pair of the rollers.  
      During the rolling, the unvulcanized rubber member extruded from the cap is rolled through the opening portion whose configuration is also close to a cross-sectional configuration along a transverse direction of the elongated rubber strip.  
      Further, the control means controls at least one of an extruding amount per an hour of the unvulcanized rubber extruded by using the extruder, and a rotational speed of the pair of the rollers, so as not to form an unvulcanized rubber bank on the pair of the rollers.  
      Since a rubber bank is not formed on the pair of the rollers, neither unnecessary unvulcanized rubber nor foreign matters (unnecessary unvulcanized rubber peeled off from the roller surface) are deposited on a roller surface and on the elongated rubber strip, respectively.  
      Regarding the description of “a rubber bank is not formed on the pair of the rollers”, it includes an extremely small amount of rubber bank (which, for example, is caused by a rubber extruding amount or an error of the rotational number of the rollers) formed within a range which does not form corrugations at the taper portions of the resultant elongated rubber strip. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a perspective view of an extruder and a roller die;  
       FIG. 2 (A) is a perspective view of a cutter;  
       FIG. 2 (B) is a side view of the cutter;  
       FIG. 3  is a perspective view of a cutter according to another embodiment of the present invention;  
       FIG. 4  is a perspective view of a cutter according to yet another embodiment of the present invention;  
       FIG. 5 (A) is a perspective view of a rubber sheet;  
       FIG. 5 (B) is a cross-sectional view of the rubber sheet shown in  FIG. 5 (A) cut along a line  5 (B)- 5 (B);  
       FIG. 5 (C) is a cross-sectional view of the rubber sheet shown in  FIG. 5 (A) cut along a line  5 (C)- 5 (C);  
       FIG. 6  is a perspective view of a drum in the middle of being wound by an elongated rubber sheet;  
       FIG. 7  is a perspective view of the elongated rubber strip and the drum after a trimming;  
       FIG. 8 (A) is a plan view of a rubber sheet;  
       FIG. 8 (B) is a cross-sectional view of the rubber sheet shown in  FIG. 8 (A) cut along a line  8 (B)- 8 (B);  
       FIG. 9 (A) is a plan view of vicinities of end portions in a longitudinal direction of an elongated rubber strip;  
       FIG. 9 (B) is a cross-sectional view of the elongated rubber strip shown in  FIG. 9 (A) cut along a line  9 (B)- 9 (B);  
       FIG. 10  is a perspective view of an elongated rubber strip according to another embodiment of the present invention;  
       FIG. 11  is an appearance perspective view of a rubber roller according to an embodiment of the present invention;  
       FIG. 12  is a side view of the rubber roller;  
       FIG. 13 (A) is a view of a target cross-sectional configuration of an elongated rubber strip;  
       FIG. 13 (B) is a view of a configuration of a cap;  
       FIG. 14  is a block diagram of a control system of the rubber roller;  
       FIG. 15 (A) is a side view of a rubber roller according to an embodiment of the present invention;  
       FIG. 15 (B) is a cross-sectional view in a transverse direction of an unvulcanized rubber discharged from a cap;  
       FIG. 15 (C) is a cross-sectional view in a transverse direction of a rubber strip elongated by a roller head;  
       FIG. 16  is a front view of the cap;  
       FIG. 17  is a front view of the roller head;  
       FIG. 18  is a block diagram of an electric system;  
       FIG. 19  is an explanatory view illustrating a direction in which a rubber is rolled;  
       FIG. 20  is a perspective view of a 2-roller die for manufacturing a conventional inner liner;  
       FIG. 21  is a perspective view of a 1-roller die for manufacturing a conventional inner liner;  
       FIG. 22  is a view of a calendar roll involving a conventional knead-back;  
       FIG. 23  is a view of a conventional 1-roller die;  
       FIG. 24 (A) is a side view of a conventional roller on which a rubber bank is formed;  
       FIG. 24 (B) is a front view of a cap;  
       FIG. 24 (C) is a front view of another cap;  
       FIG. 24 (D) is a cross-sectional view along a transverse direction of a rolled rubber sheet rolled by a roller head;  
       FIG. 25  is a cross-sectional view along a transverse direction of the rolled rubber sheet on which a swollen-out portion has been formed;  
       FIG. 26 (A) is a side view of a conventional roller on which a rubber bank is not formed;  
       FIG. 26 (B) is a cross-sectional view in a transverse direction of an unvulcanized rubber discharged from a cap;  
       FIG. 26 (C) is a cross-sectional view along a transverse direction of a rolled rubber sheet rolled by a roller head; and  
       FIG. 27  is an explanatory view illustrating a direction in which a rubber is rolled by a conventional apparatus. 
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION  
     First Embodiment  
      With reference to the drawings, i.e., FIGS.  1  to  5 , a method of manufacturing a thin rubber member according to a first embodiment of the present invention will be explained, hereinafter.  
      An Apparatus for Manufacturing an Elongated Rubber Strip  
      As shown in  FIG. 1 , a roller die  12  is disposed at a discharge outlet side of an extruder  10 .  
      The roller die  12  comprises an upper roller  14  and a lower roller  16 .  
      A wide groove  18  is formed at the center of the upper roller  14 .  
      The depth of the groove  18  is fixed in a roller axial direction, and groove walls at both sides of the groove  18  are inclined at an angle of about 87° with respect to a roller radial direction.  
      The upper roller  14  and the lower roller  16  are rotated by an unillustrated driving apparatus in a direction of arrow.  
      The extruder  10  extrudes an unvulcanized rubber composition, that is supplied into a hopper (not shown), from the discharge outlet. The rubber composition, which is extruded from the discharge outlet, is passed through the roller die  12 , and then extruded as an elongated rubber strip  20  having a fixed thickness.  
      Further, both side portions in a transverse direction of the elongated rubber strip  20  extruded from the roller die  12  form taper portions  20 A each of which is inclined at an angle of about 3° with respect to a sheet surface. Moreover, the angle of each of the transverse direction side portions of the elongated rubber strip  20  is not limited to an angle of 3°, and instead, can be another angle.  
      A cutting apparatus  22  as shown in  FIG. 2  is disposed in a direction in which a rubber sheet is extruded from the roller die  12 .  
      The cutting apparatus  22  includes an anvil  24  that supports a bottom surface of the elongated rubber strip  20 .  
      A cutter  30  is disposed above the anvil  24 , and is connected to a rod  28  of a driving apparatus  26  comprising a cylinder, a motor and the like.  
      An upper surface of the anvil  24  is horizontal, and a blade  30 A of the cutter  30  is parallel to the upper surface of the anvil  24 , and also in parallel to a transverse direction of the elongated rubber strip  20  (orthogonal to a longitudinal direction thereof).  
      The rod  28  moves in an axial direction, and the cutter  30  is moved in a direction separating from the anvil  24  at an angle of 45° with respect to the longitudinal direction of the elongated rubber strip  20 .  
      A heater (not shown) for heating the cutter  30  (for example, to a temperature of 200 to 300° C.) is housed in the cutter  30 .  
      Due to heating, the cutter  30  can cut the rubber composition easily. Further, when an ultrasonic generator is attached to the cutter  30  to oscillate the cutter  30 , the cutter  30  can also cut the rubber composition easily.  
      The cutting apparatus according to the present embodiment is of a so-called guillotine type. A cutter  32  as shown in  FIG. 3  can be slid in a transverse direction of the elongated rubber strip  20  by a driving means such as a cylinder, a motor or the like (not shown), and the elongated rubber strip  20  is cut. As shown in  FIG. 4 , a crash cutter  34  whose lower end is angled at about 90° is pressed on the elongated rubber strip  20 , and the elongated rubber strip  20  is cut.  
      A Manufacturing Process of a Rubber Sheet  
      Next, a manufacturing process of a rubber sheet will be explained.  
      First, during the initial process, the elongated rubber strip  20  is extruded and cut to a predetermined length by the cutting apparatus  22  to form a plurality of strip-shaped (rectangular) rubber sheets  36  is formed.  
      Further, a length of each of the strip-shaped rubber sheets  36  corresponds to a width as a inner liner of a tire (size in a direction orthogonal to a tire circumferential direction).  
      Next, as shown in FIGS.  5 (A) and (C), the strip-shaped rubber sheets  36  are arranged side by side in a transverse direction such that their respective taper portions  36 A (each of which is cut at an angle of 45°) in a longitudinal direction are all arranged along a uniform line, and their respective taper portions  36 B (portions extruded at an angle of about 3°) at end portions in the transverse direction are overlapped with one another, whereby a sheet of an unvulcanized inner liner  38  can be formed.  
      Since the strip-shaped rubber sheet  36  plastically deforms in a simple manner before vulcanization, as shown in  FIG. 5 (C), when the taper portion  36 A (illustrated by a chain double-dashed line) of one strip-shaped rubber sheet  36  is overlapped with the taper portion  36 A of another strip-shaped rubber sheet  36 , the taper portion  36 A of one strip-shaped rubber sheet  36  to be adhered later (illustrated by the chain double-dashed line) deforms in conformity with the taper portion  36 A of another strip-shaped rubber sheet  36  the latter taper portion  36 A adheres (illustrated by a solid line), and the surface of the adhered rubber sheets does not become irregular.  
      As a result, the inner liner  38 , all the end portions of which are tapered, can be obtained.  
      Further, a size L in  FIG. 5 (A) is that measured in a direction corresponding to a tire circumferential direction.  
      The unvulcanized inner liner  38  that is formed in such a manner as described above is used for molding a green tire in accordance with an ordinary tire manufacturing method.  
      In other words, the unvulcanized inner liner  38  is wound around an outer circumferential surface of a band-forming drum, and portions of both end portions in a circumferential direction of the inner liner  38  are overlapped with one another. Thereafter, various tire structural members such as conventional carcass ply, bead core, bead filler, belt, and tread are pasted on the inner liner  38 , and a green tire is completed.  
      Since all the portions, that are exposed at the inner surface side of the inner liner  38  disposed at an inner surface of the green tire, are formed into a tapered shape, chewing of air or an inner surface liquid into the edge portions can be prevented.  
      Further, in the present embodiment, the length of the strip-shaped rubber sheet can be changed, and the number of connections can be changed, whereby the inner liner  38  capable of accommodating various tires can be obtained.  
     Second Embodiment  
      Next, with reference to FIGS.  6  to  8 , a method of manufacturing a thin rubber member according to a second embodiment of the present invention will be explained.  
      An Apparatus for Manufacturing a Rubber Sheet  
      As shown in  FIG. 6 , in the present embodiment, first, the elongated rubber strip  20  extruded from the roller die  12  (not shown in  FIG. 6 ) is spirally wound around an outer circumferential surface of a drum  40 , which has a fixed diameter and rotates in a direction of arrow, with the taper portions  20 A overlapped with one another.  
      Next, as shown in  FIG. 7 , both end portions in the drum axial direction of the elongated rubber strip  20 , which is spirally wound around the drum, are trimmed by a cutter or the like so as to be in parallel to the drum circumferential direction.  
      During the trimming, the cutter is inclined at an angle of 45° with respect to the sheet surface so that the cut surface forms an angle of 45° with respect to the sheet surface.  
      Next, the trimmed cylindrical elongated rubber strip  20  is cut by the cutter or the like along the drum axial direction (chain double-dot line portion in  FIG. 7 ), and an inner liner  42  for one tire as shown in  FIG. 8  is obtained.  
      When the trimmed cylindrical elongated rubber strip  20  is cut along the drum axial direction, the cutter is also inclined at an angle of 45° with respect to the sheet surface so that the cut surface forms an angle of 45° with respect to the sheet surface.  
      Also in the present embodiment, the inner liner  42 , all the end portions of which, are tapered can be obtained.  
      In the present embodiment, the length and the width of the inner liner  42  can be changed in accordance with a tire due to an adjustment of a diameter of the drum  40 , the number of cuts of elongated the rubber strip along the drum axial direction or the number of spiral winds.  
      Further, as for the drum  40 , drums having various diameters are prepared in advance, among them, the drum  40  can be selected in accordance with the size of the inner liner  42 . Further, the drum  40  having a structure in which the diameter of the drum  40  can be larger or smaller can be used.  
      Moreover, in the present embodiment, after the elongated rubber strip  20  has been spirally wound around the drum, both end portions of the elongated rubber strip  20  in the drum axial direction are trimmed. As shown in  FIG. 9 (A), the vicinity of the end portion in the longitudinal direction of the elongated rubber strip  20  before the elongated rubber strip  20  is wound around the drum is diagonally cut, the diagonal portion is then removed, and the end portion in the longitudinal direction of the elongated rubber strip  20  is formed into a tapered shape as seen from a plan view. Accordingly, when the elongated rubber strip  20  is spirally wound around the drum, both end portions of the elongated rubber strip  20  in the drum axial direction can be made parallel to the circumferential direction of the drum.  
      Moreover, when the diagonal portion is removed, the cutting of the diagonal portion is carried out in such a way that the cut surface is inclined at an angle of 45°, for example, with respect to the sheet surface (see  FIG. 9 (B)).  
      The elongated rubber strip  20  of the present embodiment has the taper portions  20 A formed at both end portions in the transverse direction, and each of the taper portions  20 A has a fixed thickness in the transverse direction. As shown in  FIG. 10 , the cross section of the elongated rubber strip  20  can be formed into a triangle (including only the taper portions  20 A).  
      Even in a case of the elongated rubber strip  20  whose cross section is a triangle, if the taper portions  20 A are overlapped with one another and spirally wound around the drum at a fixed pitch, an inner liner having a fixed thickness can be formed.  
      The cylindrical inner liner can be used unchanged.  
      For instance, in a case in which a green tire is manufactured, the elongated rubber strip  20  is spirally wound around the outer circumferential surface of the drum, and the cylindrical inner liner can be obtained around the outer circumferential surface of the drum.  
      Then, tire structural members such as a bead ring, a carcass ply, a side wall rubber, a belt, and a tread are pasted on the drum having the inner liner formed thereon, and a green tire can be formed.  
      Moreover, in the present embodiment, a method of manufacturing an inner liner for a tire has been explained. It is a matter of course that the present invention can manufacture a rubber sheet for other applications.  
     Third Embodiment  
      With reference to FIGS.  11  to  14 , a rubber roller  110  according to a third embodiment of the present invention will be explained.  
      An outlook perspective view of the rubber roller  110  according to the present embodiment is shown in  FIG. 11 , and a side view thereof is shown in FIG.  12 .  
      The rubber roller  110  sequentially molds an elongated rubber strip  101  for forming a thin gauge sheet as a tire structural member.  
      The elongated rubber strip  101  is molded into a flat strip shape having taper portions  101 A and  101 A in which both edge portions are inclined in a tapered manner, and while the taper portions  101 A are sequentially overlapped with one another, a thin gauge sheet is formed.  
      As shown in  FIGS. 11 and 12 , the rubber roller  110  comprises an extruder  111 , a gear pump  112 , a rectifier tube  113 , a cap  115  of a head  114 , and a pair of calendar roll  116  in this sequential order. An unvulcanized rubber injected into the extruder  111  is molded, and sequentially discharged from the calender rolls  116  as the elongated rubber strip  101 .  
      The extruder  111  extrudes the injected unvulcanized rubber or the like to the gear pump  112 , while kneading the unvulcanized rubber by the rotation of the screw.  
      The gear pump  112  is a metering discharge pump which controls an amount of the unvulcanized rubber extruded from the extruder  111  to a discharge amount on the basis of a rotational speed of the gear, and discharges a certain amount of the unvulcanized rubber to the rectifier tube  113 .  
      The rectifier tube  113  is a distance extender tube that connects the gear pump  112  and the cap  115  of the head  114  to form an appropriate distance therebetween, and can be interposed therebetween as needed.  
      When the unvulcanized rubber is discharged from the gear pump  112 , concentration of the discharge of the rubber may often occur. Therefore, if a distance from the gear pump  112  to the head  114  is short, a degree at which the head  114  is filled with the rubber may vary. Accordingly, the rectifier tube  113  is interposed between the gear pump  112  and the cap  115  so as to prevent uneven filling of the unvulcanized rubber into the head  114 . Consequently, filling of the unvulcanized rubber can appropriately be maintained and stabilized.  
      The cap  115  of the head  114  is formed into a configuration substantially similar to a target cross-sectional configuration of the elongated rubber strip  101  to be molded.  
      As shown in  FIG. 13 (A), the target cross-sectional configuration of the elongated rubber strip  101  is formed into a flat plate shape having taper portions  101   a  and  101   a , each of which is inclined in a tapered manner, at both edge portions. As shown in  FIG. 13 (B), the cap  115  is provided with taper portions at both end edges, and is formed into an outlook configuration substantially similar to the target cross-sectional configuration of the elongated rubber strip  101 .  
      Tip ends of the taper portions of the cap shape are cut off.  
      The cap  115  is formed into a configuration similar to the target cross-sectional configuration of the elongated rubber strip  101 , whereby occurrence of a rubber drift is prevented so that a stable elongated rubber strip  101  can be obtained.  
      Further, when the elongated rubber strip  101  having taper portions at both end portions is molded, the cap  115  is also formed into a configuration in which taper portions are provided at both end portions, and accordingly, a rubber volume is adjusted, and a more stable elongated rubber strip  101  can be molded.  
      An unvulcanized rubber that is formed so as to correspond to the shape of the cap  115  is discharged into the calendar roll  116  comprising an upper roll and a lower roll.  
      The unvulcanized rubber discharged from the cap  115  is nipped by the upper roll and the lower roll of the calendar roll  116  whose outer circumferential surface is respectively formed into a predetermined configuration, and is shaped to the target cross-sectional configuration of the elongated rubber strip  101 , whereby a final elongated rubber strip  101  is formed and sequentially fed.  
      In order to form the target cross-sectional configuration of the elongated rubber strip  101  without producing a rubber to be kneaded back, a proper amount of rubber necessary for forming the target cross-sectional configuration of the elongated rubber strip  101  must be consistently discharged and supplied by the gear pump  112 .  
      Due to a change of temperature or a micro variation of rubber properties, an amount of rubber discharged by the gear pump  112  slightly changes. This change considerably influences the width of the elongated rubber strip  101 .  
      Therefore, the rubber roller  110  of the present invention comprises a sheet width control means  120  that feedback-controls the width of the elongated rubber strip  101  discharged from the calendar roll  116 .  
      In other words, a width sensor  117 , which is an optical sensor that optically detects a width of the elongated rubber strip  101 , is provided at a downstream side of the calendar roll  116  (see  FIG. 11 ), and as shown in  FIG. 14 , the sheet width control means  20  feedback-controls the gear pump  112  on the basis of the detected width of the elongated rubber strip  101  by the width sensor  117 .  
      As shown in  FIG. 14 , at the same time, the rubber roller  110  of the present invention comprises a pressure control means  125  that controls a supply pressure into an unvulcanized rubber with respect to the extruder  111  for supplying the unvulcanized rubber into the gear pump  112 .  
      For this reason, a pressure sensor  126  is provided at an inlet of the gear pump  112 . On the basis of the detected pressure by the pressure sensor  126 , the pressure control means  125  feedback-controls the extruder  111  so that an unvulcanized rubber is supplied stably at a constant range of pressure.  
      In this way, the sheet width control means  120  feeback-controls the gear pump  112 , from which an unvulcanized rubber is supplied at a constant range of pressure, to discharge a proper amount of rubber in accordance with a micro change while observing the width of the elongated rubber strip  101 . Accordingly, the width accuracy of the elongated rubber strip  101  can be maintained higher.  
      As described above, in the rubber roller  110  of the present invention, since the elongated rubber strip  101  having a highly accurate cross-sectional configuration can be molded without producing a rubber to be kneaded back, an occurrence of deterioration of a rubber quality due to a repetition of a knead-back can be prevented, and a knead-back operation is not required. Accordingly, the rubber roller  110  is able to take advantage of space, as equipment that can be manufactured simply and inexpensively, and causes fewer troubles and hardly inhibits productivity.  
      Further, in the present embodiment, the sheet width control means  20  feedback-controls the gear pump  112  on the basis of the detected width by the width sensor  117 , and the pressure control means  125  feedback-controls the extruder  111  on the basis of the detected pressure by the pressure sensor  126 . As far as the elongated rubber strip  101  having a highly accurate cross-sectional configuration can be molded without producing a rubber to be kneaded back, motors (not shown) for driving the gear pump  112  and the extruder  111  can be controlled so as to have a constant rotational speed (i.e., have a constant discharge amount).  
      Moreover, another control means which controls a rotation of a motor that drives the calendar roll  116  can be provided so as to control a rotation of the motor on the basis of the detected width by the width sensor  117 .  
     Fourth Embodiment  
      On the basis of FIGS.  15  to  19 , a rubber roller  210  according to a fourth embodiment of the present invention will be explained.  
      As shown in  FIG. 15 (A), the rubber roller  210  of the present embodiment has a rubber extruder  212 .  
      The rubber roller  210  aims to obtain an elongated rubber strip  242  which has a cross-sectional configuration as shown in  FIG. 15 (C), whose thickness is constant at an intermediate portion in a transverse direction, and which has taper portions, each of which has a thickness gradually decreasing toward the end portions in the transverse direction, at both sides of the elongated rubber strip  242 .  
      A laterally elongated opening  216 , from which an unvulcanized rubber is extruded, as shown in  FIG. 16  is formed at a cap  214  of a rubber extruder  212 .  
      The opening  216  has an entirely linear lower edge  218 , and an upper edge  220  whose central portion  220 A is linear and is parallel to the lower edge  218  and which has inclining surfaces  220 B formed at both end portions. Further, vertical portions  221  perpendicular to the lower edge  218  are formed at both end portions of the opening  216 .  
      In other words, the opening  216  is formed into a configuration substantially similar to a cross-sectional configuration of the elongated rubber strip  242 .  
      The opening  216  of the present embodiment has a lateral width W1 of 100 mm, a height H1 of the opening  216  central portion of 1 mm, a height h of the vertical portion  221  of 0.5 mm, and an angle θ1 of the inclining surface  220 B with respect to the lower edge  218  of 3°.  
      As shown in  FIG. 15 (A), a roller head  222  is provided at a downstream side in a direction a rubber is extruded, of the cap  214 .  
      As shown in  FIG. 17 , the roller head  222  comprises an upper roller  224  and a lower roller  226 .  
      The lower roller  226  has a constant diameter in an axial direction.  
      A groove  228  is formed at an intermediate portion in an axial direction.  
      The groove  228  has a central portion  228 A whose depth is constant, and has inclining surfaces  228 B, each of which depth gradually decreases, at both end portions of the groove  228 .  
      In the present embodiment, a groove width W2 is 98 mm, a groove depth H2 of the central portion of the groove is 0.8 mm, and an angle θ2 of the inclining surface (with respect to a rotational axis) is 3°.  
      The upper roller  224  and the lower roller  226  are kept in contact with each other at their outer circumferential portions excluding the groove  228 . An opening portion formed by the groove  228  and the lower roller  226  is a molding portion  230  for rolling an unvulcanized rubber, and has a configuration substantially similar to a cross-sectional configuration of the elongated rubber strip  242 .  
      The upper roller  224 , the lower roller  226 , and a screw  232  of the rubber extruder  212  are respectively rotated by unillustrated motors.  
      As shown in  FIG. 18 , a motor  234  for rotating the upper roller  224  and the lower roller  226 , and a motor  236  for rotating the screw  232  of the rubber extruder  212  are connected to a controller  238  which controls rotational frequencies of the motors  234  and  236 .  
      Operation  
      Next, a description of an operation of the rubber roller  210  according to the present embodiment will be made.  
      First, a sheet-shaped unvulcanized rubber member  240  is extruded from the opening  216  of the cap  214  of the rubber extruder  212 .  
      A cross-sectional configuration in a transverse direction of the unvulcanized rubber member extruded from the cap  214  (see  FIG. 15 (B)) is similar to that along a transverse direction of the elongated rubber strip  242 , and has a width and a thickness which are slightly larger than those of the opening  216  of the cap  214 .  
      The vertical portions  221  each having a height h of 0.5 mm are formed at both end portions of the opening  216  because, if heights of portions in the vicinities of both end portions (taper tip ends) are insufficient, a case may occur that an unvulcanized rubber is not fully extruded from the opening  216 .  
      The height h of the vertical portion  221  is experimentally determined and set so that an unvulcanized rubber can be extruded evenly.  
      The unvulcanized rubber member extruded from the cap  214  is rolled by the roller head  222 .  
      At this time, a controller  238  controls both the motor  236  of the rubber extruder  212  and the motor  234  of the roller head  222  so as not to form a rubber bank on the roller head  222 .  
      In the present embodiment, the unvulcanized rubber member  240  extruded from the cap  214  is rolled by the molding portion  230  which is formed into a configuration similar to a cross-sectional configuration in the transverse direction of the elongated rubber strip  242  and which is slightly smaller than a cross-section along the transverse direction of the elongated rubber strip  242 .  
      By rolling the unvulcanized rubber member  240  without forming a rubber bank on the roller head  222 , a direction in which the unvulcanized rubber member  240  is rolled (direction of arrow shown in  FIG. 19 ) becomes uniform in the transverse direction of the elongated rubber strip  242 . As a result, a shrunk amount of the sheet which has been rolled becomes uniform in the transverse direction of the elongated rubber strip  242 , and corrugations are not formed on the taper portions which have been cooled, whereby the elongated rubber strip  242  having excellent properties can be obtained.  
      Since the present invention is structured so as not to form a rubber bank on the roller head  222 , no undesired unvulcanized rubber is deposited on the roller surface, and no foreign matter (undesired unvulcanized rubber that has been stripped off from the roller surface) is deposited on the elongated rubber strip  242 .  
      Moreover, for example, there is a case in which an extremely small amount of a rubber bank is formed on the head  22  due to an error of the rubber extruding amount or the rotational frequency of the roller head. Unless corrugations are formed on the taper portions of the elongated rubber strip  242 , even if the small amount of the rubber bank is formed, this comes within a category that “no rubber bank is formed on the roller head” as referred herein.  
     Industrial Applicability  
      As described above, the method of manufacturing a thin rubber member according to the present invention is suitable for manufacturing a rubber sheet that is used as a tire structural member, for example, an inner liner or the like.  
      Further, the rubber roller and the method of rolling a rubber according to the present invention are suitable for manufacturing an elongated rubber strip that is used for manufacturing the thin rubber member.