Abstract:
An apparatus for making strips of fiber-containing rubber is disclosed, wherein the short fibers in each of the strips are oriented in the widthwise direction of the strip. The apparatus comprises: a screw section for pushing out a fluid mixture of unvulcanized rubber and short fibers as fiber-containing rubber; an orienting section comprising a radially extending path provided with an inlet in the center thereof and a looped nozzle on the periphery thereof so that the fiber-containing rubber is expanded circumferentially while flowing radially from the center towards the periphery; and a dividing section comprising a plurality of cutters arranged around the looped nozzle so that the fiber-containing rubber extruded from the looped nozzle is circumferentially divide into a plurality of strips.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to an apparatus for making a strip of fiber-containing rubber, more particularly to an extruder being capable of extruding a plurality of strips of fiber-containing rubber whose short fibers are oriented in the widthwise direction of the strip. 
   2. Related Art 
   In making rubber products such as pneumatic tire for example, for the purpose of reinforcing its rubber component, or providing a rubber component with anisotropy or the like, fiber-containing rubber compounds are sometimes used to make such rubber component or layer of the product. In making a pneumatic tire, sometimes, an unvulcanized rubber strip containing short fibers oriented in a specific direction is used to make a specific tire component. For example, using a strip including short fibers oriented in the widthwise direction thereof, a tread rubber can be made by winding the strip around a drum. If a relatively wide strip is wound while keeping the widthwise direction thereof almost parallel to the axis of the drum, the fibers in the tread rubber are oriented in the widthwise direction of the tread which may improve steeling stability without deteriorating ride comfort. If a relatively narrow strip is wound while keeping the widthwise direction thereof almost perpendicular to the axis of the drum, the fibers in the tread rubber are oriented in the radial direction of the tire which may improve road grip, traction, wet grip (on-the-ice performance) and the like. 
   It is therefore, an object of the present invention to provide an apparatus by which a plurality of rubber strips containing short fibers oriented in the widthwise direction thereof can be continually made at the same time, allowing for more efficient production and downsizing and simplifying of the apparatus. 
   BRIEF SUMMARY OF THE INVENTION 
   According to the present invention, an apparatus for making strips of fiber-containing rubber comprises 
   a screw section for pushing out a fluid mixture of unvulcanized rubber and short fibers as fiber-containing rubber, 
   an orienting section comprising a radially extending path for the fiber-containing rubber provided with an inlet in the center thereof and a looped nozzle on the periphery thereof so that the fiber-containing rubber is expanded circumferentially while flowing radially from the center towards the periphery, 
   a dividing section comprising a plurality of cutters arranged around the looped nozzle so that the fiber-containing rubber extruded from the looped nozzle is circumferentially divide into a plurality of strips, whereby the short fibers in each of the strips are oriented in the widthwise direction of the strip. 

   
     An embodiment of the present invention will now be described in detail in conjunction with the accompanying drawings. 
       FIG. 1  is a side elevational view of an apparatus for making strips of fiber-containing rubber according to the present invention. 
       FIG. 2  is a cross sectional view of the head thereof. 
       FIG. 3  is a front view of the head showing an upper half thereof. 
       FIG. 4  is an enlarged perspective partial view of the head. 
       FIG. 5  is a perspective view of a fiber orienting path shown like a wireframe model. 
       FIG. 6  is a perspective diagram schematically showing the flow direction of the fiber-containing rubber and the orient direction of the short fibers therein. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   In the drawings, apparatus  1  for making a plurality of strips ST of fiber-containing rubber FR according to the present invention comprises a screw section  2 , an orienting section  3 , and a dividing section  4 . In this embodiment, the apparatus  1  is incorporated in a tire manufacturing system. 
   The screw section  2  comprise a main body  20  having a cylindrical mixing chamber  21 , a screw  22  disposed therein, and an electric motor M for rotating the screw  22 . Using an inlet  23  provided on the backside of the main body  20 , raw rubber materials and short fibers are put into the cylindrical mixing chamber  21 . By rotating the screw  22 , the raw rubber materials and short fibers in the cylindrical mixing chamber  21  are mixed into fiber-containing raw rubber FR, and the mixture is pushed towards an outlet  24  at the front end of the main body  20 . 
   The orienting section  3  comprises a first orienting path  31  extending in a direction (horizontal direction) and a second orienting path  32  extending radially from the front end of the first orienting path  31  to a looped nozzle  33 . 
   The first orienting path  31  comprises a tapered path  31 T and a substantially constant diameter path  31 C. The tapered path  31 T has a rear end which is connected to the outlet  24  of the screw section  2  and into which the fiber-containing rubber FR is pushed. The tapered path  31 T has a shape of frustum of circular cone tapering from the rear end to the front end thereof. The substantially constant diameter path  31 C extends from the front end of the tapered path  31 T to its front end while maintaining a substantially constant inside diameter D 1  so as to have a shape of circular cylinder. Therefore, the fiber-containing rubber FR is decreased in the outside diameter while passing though the tapered path  31 T, but during passing though the path  31 C, the outside diameter maintains a constant value. As a result, the short fibers are gradually oriented in the flowing direction, and at the front end of the substantially constant diameter path  31 C, the orientation in the flowing direction is maximized. In this embodiment, the first orienting path  31  is formed by a through hole of an orifice ring  34  attached to the front of the main body  20 . 
   The second orienting path  32  is defined between a collision wall WC and an opposite guide wall WG which have circular forms of the substantially same diameter. At the center of the guide wall WG, the front end of the first orienting path  31  opens to the inside of the second orienting path  32 , and the center of the collision wall WC confronts with the opening of the first orienting path  31 . The guide wall WG is flat and extends radially from the edge of the opening of the first orienting path  31  at right angles with respect to the axial direction J of the first orienting path  31  or the flowing direction. The collision wall WC is, aside from a central portion, flat and parallel with the guide wall WG. Therefore, the second orienting path  32  extends radially from its center to the periphery which opens as the looped nozzle  33 . 
   The fiber-containing rubber FR going into the second orienting path  32  comes into collision with the collision wall WC and turns its flowing direction by 90 degrees and the fiber-containing rubber FR flows radially. Thus, the fiber-containing rubber FR turns from the columnar state Ga in the constant diameter path  31 C to a radially spreading disk-like state Gb as shown in  FIG. 6 . As the fiber-containing rubber FR spreads radially, the rubber expands circumferentially and the fibers therein are oriented in the circumferential direction. The orientation in the circumferential direction is maximized at the looped nozzle  33 . 
   In order to effectively orient the short fibers in the circumferential direction at the looped nozzle  33 , the gap (d) between the guide wall WG and the collision wall WC is set in a range of from 0.5 to 10.0 mm, and the diameter D 1  of the substantially constant diameter path  31 C is set in a range of not more than 1/3 times the diameter D 2  of the second orienting path  32  at the looped nozzle  33 . 
   The central portion of the collision wall WC may be a flat face, but it is preferably formed as a protruding circular conical surface  32 P whose cone axis is aligned with the axis J of the first orienting path  31  in order to further the orientation and make the flow volume even in every radial direction. The circular conical surface  32 P protrudes towards the front end of the substantially constant diameter path  31 C, and the amount of protrusion (h) is preferably set in a range of from 0.5 to 1.2 times the gap (d) of the second orienting path  32 , and the corn angle alpha is preferably set in a range of 90 to 150 degrees, and the diameter of the base of the corn is substantially equal to the diameter of the inlet of the second orienting path  32 , namely, the above-mentioned diameter D 1 . 
   The above-mentioned dividing section  4  comprises cutters  6  disposed near the looped nozzle  33  and extending across the looped nozzle  33 . In this embodiment, six cutters  6  are equiangularly arranged around the looped nozzle  33 . The cutter  6  may be a wire or cord, but in this example, a platy blade is used. As shown in  FIG. 4 , the cutters  6  protrude into a periphery portion of the second orienting path  32  through radially extending slots which are formed on the collision wall WC. 
   In this embodiment, the above-mentioned guide wall WG is defined by the front surface of a flange  35  of the orifice ring  34 . The collision wall WC is defined by the rear surface of a cap plate  36 . The cap plate  36  is disposed on the front of the orifice ring  34  and supported by support arms  37  while leaving the above-mentioned gap (d). 
   The support arm  37  comprises: a radially extending part  37 A extending radially outwardly from the periphery of the cap plate  36 ; an axially extending part  37 B extending across the looped nozzle  33  from the radially extending part  37 A and provided with a slot  38  in the rear end portion thereof or the other end portion than the part  37 A; a wedge-shaped lock pin  37 C inserted into the slot  38  so as to protrude radially inwardly to the backside of the flange  35  so as to lock the flange  35 ; and an adjusting bolt  37 D provided on the axially extending part  37 B. Therefore, a plurality of the adjusting bolts  37 D are arraigned around the circular flange  35 . By fastening the adjusting bolts  37 D, the cap plate  36  is secured to the circular flange  35 . By adjusting the bolts  37 D, the centers of the guide wall WG and collision wall WC can be aligned. By controlling the radially inward protrusion of the wedge-shaped lock pins  37 C, the gap and parallelness between the two walls WG and WC can be adjusted. In the above-explained example, the support arms  37  are constructed to extend from the cap plate  36  to the orifice ring  34 . But, it is also possible to construct them to extend reversely from the orifice ring  34  to the cap plate  36  to secure the cap plate  36  between the adjusting bolts  37 D. 
   In this embodiment, the above-mentioned cutters  6  are disposed at the positions of the support arms  37 , and each of the cutter  6  is fixed to a side face of the radially extending part  37 A of one of the support arms  37  as shown in  FIG. 4 . After the cutters  6  divide the fiber-containing rubber FR into a plurality of strips ST, the strips ST are guided and moved radially for a short distance from the looped nozzle  33 . Thus, radially increasing gaps K are formed between the adjacent strips ST, and the above-mentioned axially extending part  37 B are positioned in the gaps K. The divided strips ST are each turned in the moving direction (now radially outwards) towards the front direction by guide rollers  39  provided one for each strip ST. In this example, as shown in  FIG. 4 , each of the guide rollers  39  is mounted on the support arm  37  using an universal joint  20 , e.g. ball joint between one end of the guide roller  39  and one of the side faces of the support arm  37 . 
   By the way, on the downstream of the apparatus  1 , conveyers, take-up reels of a take-up machine, accumulators, feed units or the like may be provided according to the next stage, for example, transportation, storage, accumulation (making festoon), more specifically, winding the strip around a drum to form a tire component, applying or winding on another tire component and the like. 
   As explained above, in the apparatus according to the present invention, a plurality of strips are manufactured at the same time in spite of the simple mechanism. Therefore, the production efficiency and production cost may be improved, and not only downsizing of the apparatus itself but also downsizing of the production system for rubber article such as pneumatic tire including the apparatus may be possible.