Patent Description:
In a case where a rubber product such as a tire is manufactured, an extrusion step is available in which unvulcanized rubber is extruded by a rubber extrusion device. A screw installed inside an rubber extrusion device plasticizes unvulcanized rubber and feeds plasticized unvulcanized rubber into an extrusion flow path formed in a head of the leading end. A die including an extrusion port with a desired shape is installed at the leading end of the head, and unvulcanized rubber passes through the extrusion port. A rubber extrudate provided with the desired shape is thus manufactured (see, for example, <CIT>).

Different types of rubber have different rubber physical properties, and even for the same type of rubber, rubber physical properties vary among lots to some degree. In addition, extrusion conditions and the like vary among lots. Due to these variations, even in a case where the unvulcanized rubber is extruded using the same die, the rubber extrudate may be curved in an unintended direction with respect to the extrusion direction, preventing rubber extrudates with the desired shape from being obtained. In each case of such unintended curving, excess working man-hours are required in order to modify the back side shape of the die by machining or adjust extrusion conditions or the like.

<CIT> discloses a rubber extrusion device comprising a cylindrical cylinder, a screw disposed in an internal space of the cylinder, a head installed at a leading end of the cylinder and including an extrusion flow path communicating with the internal space, and a die attached to the head at a leading end position of the extrusion flow path, the die including an extrusion port, the rubber extrusion device further comprising a moving unit for moving the die at least in a uniaxial direction relative to the head along a leading end surface of the head, and being capable of fixing the die and the head in a desired relative position. The attachment position of the die with respect to the head may be finely adjusted in order to influence the curvature of the rubber extrudate. <CIT> discloses an extruder comprising movable pieces for influencing the flow path of the material to be extruded. <CIT> discloses an extrusion device comprising two extruders, wherein a die and a nozzle cap are positioned with respect to each other such that the direction of a strip/belt rubber extrudate can be accurately determined. <CIT> discloses an extrusion device comprising two extruders each producing a belt-like rubber which are pasted together to form an annular shape.

An object of the present invention is to provide a rubber extrusion device capable of suppressing unintended curving of a rubber extrudate and a method for manufacturing a rubber extrudate.

In order to achieve the object described above, a rubber extrusion device of the present invention comprises a cylindrical cylinder, a screw disposed in an internal space of the cylinder, a head installed at a leading end of the cylinder and including an extrusion flow path communicating with the internal space, and a die attached to the head at a leading end position of the extrusion flow path, and an extrusion port communicating with the extrusion flow path and penetrating the die in the longitudinal direction, wherein unvulcanized rubber extruded forward by the screw exits through the extrusion port as a rubber extrudate, the rubber extrusion device further comprising a moving unit for moving the die at least in a uniaxial direction relative to the head along a leading end surface of the head, and being capable of fixing the die and the head in a desired relative position. A front aperture of the extrusion flow path is set to be larger than a rear aperture of the extrusion port and the entire range of the rear aperture of the extrusion port is maintained to be disposed inside the front aperture of the extrusion flow path. The rubber extrusion device further comprises a control unit for moving the die and the head to a desired relative position by controlling operation of the moving unit, and a sensor for detecting an amount of curving, with respect to an extrusion direction, of the rubber extrudate extruded from the extrusion port, and based on the detection data from the sensor, the control unit is adapted for moving the die and the head to the desired relative position.

A method for manufacturing a rubber extrudate according to the present invention includes feeding a rubber material into an internal space of a cylindrical cylinder, extruding the rubber material forward using a screw disposed in the internal space, while mixing and kneading the rubber material, feeding resultant unvulcanized rubber into an extrusion flow path formed in a head located at a leading end of the cylinder, and extruding the unvulcanized rubber from an extrusion port as a rubber extrudate, the extrusion port communicating with the extrusion flow path and penetrating a die in the longitudinal direction, the die being attached to the head at a leading end of the extrusion flow path, wherein the method further includes placing the die and the head in a desired relative position by moving the die at least in a uniaxial direction relative to the head along a leading end surface of the head, setting a front aperture of the extrusion flow path to be larger than a rear aperture of the extrusion port and maintaining the entire range of the rear aperture of the extrusion port to be disposed inside the front aperture of the extrusion flow path, and by means of a sensor, detecting an amount of curving, with respect to an extrusion direction, of the rubber extrudate extruded from the extrusion port, and based on the detection data from the sensor, moving the die and the head to a desired relative position.

According to the present invention, the die can be moved at least in the uniaxial direction relative to the head along the leading end surface of the head. In a case where the extrusion port is moved in a direction orthogonal to the extrusion direction relative to the extrusion flow path, a change occurs in a pressure distribution (fluid flow distribution) of the unvulcanized rubber passing through the extrusion flow path and then through the extrusion port. This allows the manner of curving of the rubber extrudate to be adjusted. Thus, by moving the die relative to the head along the leading end surface of the head such that the rubber extrudate is curved in a direction opposite to the direction of unintended curving, the unintended curving of the rubber extrudate can be suppressed.

A rubber extrusion device and a method for manufacturing a rubber extrudate according to an embodiment of the present invention will be described below based on illustrated embodiments.

A rubber extrusion device <NUM> of an embodiment of the present invention illustrated in <FIG> includes a cylindrical cylinder <NUM>, a screw <NUM> disposed inside the cylinder <NUM>, and a head <NUM> disposed at a leading end of the cylinder <NUM>. A die <NUM> with an extrusion port <NUM> is attached to the head <NUM>. The rubber extrusion device <NUM> includes a moving unit <NUM> that moves the die <NUM> at least in a uniaxial direction relative to the head <NUM> along a leading end surface of the head <NUM>. Note that in <FIG>, the moving unit <NUM> and the like are omitted and not illustrated.

In the embodiment, the rubber extrusion device <NUM> further includes a sensor <NUM> and a control unit <NUM> to which detection data from the sensor <NUM> is input. A conveyor device <NUM> is disposed in front of the die <NUM> to convey, to a next step, a rubber extrudate R2 extruded from the extrusion port <NUM>.

In the drawings, the direction of arrow X and the direction of arrow Y are each illustrated as a uniaxial direction along the leading end surface of the head <NUM>. The direction of arrow X is the lateral direction (width direction) of the head <NUM>, and the direction of arrow Y is the vertical direction (height direction) of the head <NUM>. The direction of arrow X and the direction of arrow Y are orthogonal to each other. It is sufficient that the uniaxial direction extends along the leading end surface of the head <NUM>. Accordingly, the uniaxial direction is not limited to the direction of arrow X or the direction of arrow Y, and may extend obliquely along the leading end surface of the head <NUM>.

As illustrated in <FIG>, at a leading end portion of the cylinder <NUM>, an internal space is narrower toward the front. The head <NUM> includes an extrusion flow path 4a penetrating the head <NUM> in the longitudinal direction, and the extrusion flow path 4a is in communication with the internal space of the cylinder <NUM>.

The die <NUM> is attached to a leading end position of the extrusion flow path 4a of the head <NUM>. In the embodiment, the extrusion port <NUM> penetrating the die <NUM> in the longitudinal direction is shaped, in a front view, like a trapezoid extending in the lateral direction of the head <NUM> as illustrated in <FIG>. The extrusion port <NUM> has a laterally asymmetrical shape. Since the extrusion flow path 4a and the extrusion port <NUM> are in communication, unvulcanized rubber R1 pushed through the internal space of the cylinder <NUM> into the extrusion flow path 4a is extruded to pass through the extrusion flow path 4a and exit through the extrusion port <NUM> as the rubber extrudate R2. The extrusion port <NUM> is not limited to this shape, and a desired shape such as a circle, an ellipse, a semicircle, a square, a rectangle, or the like is employed.

Two holding members 7a are fixed to the head <NUM> with a lateral spacing between the holding members 7a using fixing bolts 7b penetrating the respective holding members 7a in the longitudinal direction. The die <NUM> is held by the holding members 7a so as to be movable in the lateral direction with respect to the head <NUM>.

A fixing plate <NUM> is mounted on a left side surface of the head <NUM> so as to protrude outward, and the moving unit <NUM> is installed on the fixing plate <NUM>. In the embodiment, the moving unit <NUM> includes a servo motor and a ball screw rotated and moved in the axial direction by the servo motor, and a tip of the ball screw is connected to a left side surface of the die <NUM>.

Besides, for example, a hydraulic cylinder or the like may be used as the moving unit <NUM>. The installation location of the moving unit <NUM> is not limited to the left side of the head <NUM>, and can be, for example, the right side of the head <NUM>. Note that, instead of the structure in which the die <NUM> and the moving unit <NUM> are directly connected, a structure can be provided in which, for example, the moving unit <NUM> is connected to a frame body to which the die <NUM> is attached.

Actuation of the moving unit <NUM> moves the ball screw back and forth in the lateral direction, and thus, the die <NUM> moves in the lateral direction with respect to the head <NUM>. Correspondingly, in a front view, the position of the extrusion port <NUM> changes with respect to a leading end opening of the extrusion flow path 4a. The die <NUM> can be fixed at a desired moving position, and thus, the die <NUM> and the head <NUM> can be fixed at a desired relative position along the leading end surface of the head <NUM>. The actuation of the moving unit <NUM> is controlled by the control unit <NUM> based on the detection data from the sensor <NUM>. Thus, the die <NUM> is moved to and fixed at the desired position relative to the head <NUM> under the control of the control unit <NUM>.

A procedure of a method for manufacturing a rubber extrudate according to an embodiment of the present invention will be described below.

In a case where the rubber extrudate R2 is manufactured by the rubber extrusion device <NUM>, a predetermined amount of a rubber material R such as raw rubber and a compounding agent is fed into the internal space of the cylinder <NUM>. The rubber material R is mixed and kneaded by the rotating screw <NUM>. The unvulcanized rubber R1 extruded forward by the screw <NUM> is softened to some degree (plasticized) and fed into the extrusion flow path 4a. The unvulcanized rubber R1 then passes through the extrusion flow path 4a.

The leading end opening area of the extrusion flow path 4a is partially covered by the die <NUM>, and the unvulcanized rubber R1 is extruded from the extrusion port <NUM> with the desired shape. Thus, the rubber extrudate R2 provided with a desired cross-sectional shape is manufactured. For example, the rubber extrudate R2, such as a strip-like tire member provided with a predetermined shape, is manufactured according to an embodiment of the present invention. The rubber extrudate R2 is extruded while being conveyed to the next step by the transfer conveyor device <NUM>.

In a case where the unvulcanized rubber R1 varies in rubber physical properties or due to extrusion conditions or the like, the rubber extrudate R2 may be curved in an unintended direction (lateral direction or vertical direction) as illustrated in <FIG> even in a case where the rubber extrudate is extruded from the extrusion port <NUM> with the same shape. Note that, in <FIG>, the center position of the extrusion port <NUM> in the lateral direction (width direction) is indicated by a dot-dash line CL, and the center position of the rubber extrudate R2 in the lateral direction (width direction) is indicated by a dot-dash line M. In <FIG>, at a position located at a forward distance L from the die <NUM>, the lateral center position M of the rubber extrudate R2 is shifted rightward by an amount of shift d with respect to the reference position CL of the extrusion port <NUM>, and the rubber extrudate R2 is curved rightward (by an amount of curving d).

Curving of the rubber extrudate R2 in a specific direction as illustrated in <FIG> instead of straight extrusion is expected to be caused by a combination of various factors such as a variation in the rubber physical properties of the unvulcanized rubber R1, and extrusion conditions (pressure, temperature, flow velocity, and the like), matching between the cylinder <NUM> and the screw <NUM>, and the like. The present inventors have found that the manner of curving (the amount or direction of curving) of the rubber extrudate R2 is changed by varying the relative position between the extrusion flow path 4a and the extrusion port <NUM> in a front view, and based on the findings, have created the present invention.

Thus, in an embodiment of the present invention, the die <NUM> positioned as illustrated in <FIG> is moved leftward with respect to the head <NUM>, as illustrated in <FIG>. Such a change in the relative position between the extrusion flow path 4a and the die <NUM> in a front view changes a pressure distribution (fluid flow distribution) of the unvulcanized rubber R1 passing through the extrusion flow path 4a and then through the extrusion port <NUM>. Correspondingly, a leftward curving force acts on the rubber extrudate R2 to allow the manner of curving of the rubber extrudate R2 to be adjusted.

In a case where the die <NUM> is moved further leftward with respect to the head <NUM> as illustrated in <FIG>, the leftward curving force acting on the rubber extrudate R2 becomes excessively strong, thus curving the rubber extrudate R2 leftward. Thus, in an embodiment of the present invention, the relative position between the extrusion flow path 4a and the extrusion port <NUM> in a front view is appropriately adjusted to establish a fixed state as illustrated in <FIG>. Then, the rubber extrudate R2 is extruded. As described above, by moving the die <NUM> relative to the head <NUM> along the leading end surface of the head <NUM> such that the rubber extrudate R2 is curved in a direction opposite to the direction of unintended curving, the unintended curving of the rubber extrudate R2 can be suppressed. As a result, the curving of the rightward curved rubber extrudate R2 is corrected, enabling obtainment of a rubber extrudate R2 provided with a desired straight shape corresponding to the shape of the extrusion port <NUM>.

Thus, according to an embodiment of the present invention, even in a case where a variation attributed to rubber physical properties or extrusion conditions or the like occurs, the rubber extrudate R2 having a desired shape inhibited from being unintentionally curved can be stably manufactured by controlling the relative position between the die <NUM> and the head <NUM> along the leading end surface of the head <NUM>. Additionally, an embodiment of the present invention eliminates or minimizes a need for excess work performed in the related art to modify the shape of the die <NUM> by machining or adjust the extrusion conditions or the like in each case of a variation attributed to the rubber physical properties or the extrusion conditions or the like. This is advantageous in improving the productivity of the rubber extrudate R2. Moreover, according to an embodiment of the present invention, it is only required that the moving unit <NUM> moving the die <NUM> is provided at the leading end position of the extrusion flow path 4a. Thus, an embodiment of the present invention can be easily applied to existing rubber extruders.

In the embodiment, the sensor <NUM> is used to successively detect the amount of lateral shift d of the lateral center position M of the rubber extrudate R2 relative to the lateral center position CL of the extrusion port <NUM> at a position located at the forward distance L from the die <NUM>. The control unit <NUM> successively controls the position of the die <NUM> (the relative position between the die <NUM> and the head <NUM> along the leading end surface of the head <NUM>) to make the amount of shift d closer to zero (the control unit <NUM> provides feedback control). The amount of shift d of the rubber extrudate R is largest at a position located at a distance L of approximately <NUM>, and thus, the sensor <NUM> detects the amount of shift d, for example, at a position located at a distance L of <NUM> to <NUM>.

In a case where there is some accumulation of correlation data between fluctuation parameters such as rubber physical properties and extrusion conditions and the relative position between the die <NUM> and the head <NUM> along the leading end surface of the head <NUM> and the manner of curving of the rubber extrudate R2 in a case of extrusion in the relative position, the correlation data is input into the control unit <NUM> in advance. In a case where extrusion of the rubber extrudate R2 is started, the rubber extrusion device is preset by inputting actual fluctuation parameters to the control unit <NUM> and based on these data and the correlation data described above, which has been input in advance, placing the die <NUM> at a predetermined position with respect to the head <NUM>. Extrusion is then performed such that the rubber extrudate R2 has a desired shape prevented from being unintentionally curved.

In a case where the rubber extrudate R2 used, for example, as a tire component is manufactured using an embodiment of the present invention, the rubber extrudate R2 can have the desired shape inhibited from being unintentionally curved. Thus, manufacturing a tire using the rubber extrudate R2 is advantageous in improving the uniformity of the tire.

In a case where the uniaxial direction in which the die <NUM> is moved relative to the head <NUM> is set in the extension direction of the extrusion port <NUM> (the direction in which the extrusion port <NUM> extends the longest in a front view) as in the embodiment, a significant change is easily made to the pressure distribution (fluid flow distribution) of the unvulcanized rubber R1 passing through the extrusion flow path 4a and then through the extrusion port <NUM>. Thus, the unintended curving of the rubber extrudate R2 is easily suppressed.

In another embodiment of the rubber extrusion device <NUM> illustrated in <FIG>, the die <NUM> is configured to be movable not only in the lateral direction but also in the vertical direction relative to the head <NUM> along the leading end surface of the head <NUM>. Specifically, the moving unit <NUM> is disposed above the head <NUM>. The moving unit <NUM> includes a servo motor and a ball screw rotated and moved in the axial direction by the servo motor, and a tip of the ball screw is connected to an upper surface of the die <NUM>. The moving unit <NUM> is connected by a connecting arm 7c to another moving unit <NUM> disposed on the left side of the head <NUM>. The die <NUM> is held by the holding member 7a so as to be movable in the lateral direction and the vertical direction with respect to the head <NUM>.

The moving unit <NUM> disposed on the left side of the die <NUM> moves the die <NUM> and the moving unit <NUM> disposed above the die <NUM> via the connecting arm 7c, in the lateral direction with respect to the head <NUM> along the leading end surface of the head <NUM>. Accordingly, in the embodiment, the die <NUM> is movable in a discretionary direction relative to the head <NUM> along the leading end surface of the head <NUM>.

In the embodiment, further detailed changes can be made to the pressure distribution (fluid flow distribution) of the unvulcanized rubber R1 passing through the extrusion flow path 4a and then through the extrusion port <NUM>. This allows the manner of curving of the rubber extrudate R2 to be more specifically adjusted. Thus, the unintended curving of the rubber extrudate R2 can be reliably suppressed with greater accuracy.

Claim 1:
A rubber extrusion device (<NUM>) comprising
a cylindrical cylinder (<NUM>),
a screw (<NUM>) disposed in an internal space of the cylinder (<NUM>),
a head (<NUM>) installed at a leading end of the cylinder (<NUM>) and including an extrusion flow path (4a) communicating with the internal space, and
a die (<NUM>) attached to the head (<NUM>) at a leading end position of the extrusion flow path (4a), and an extrusion port (<NUM>) communicating with the extrusion flow path (4a) and penetrating the die (<NUM>) in the longitudinal direction, wherein unvulcanized rubber (R1) extruded forward by the screw (<NUM>) exits through the extrusion port (<NUM>) as a rubber extrudate (R2),
the rubber extrusion device (<NUM>) comprising a moving unit (<NUM>) for moving the die (<NUM>) at least in a uniaxial direction (X, Y) relative to the head (<NUM>) along a leading end surface of the head (<NUM>), and being capable of fixing the die (<NUM>) and the head (<NUM>) in a desired relative position,
characterized in that
a front aperture of the extrusion flow path (4a) is set to be larger than a rear aperture of the extrusion port (<NUM>) and the entire range of the rear aperture of the extrusion port (<NUM>) is maintained to be disposed inside the front aperture of the extrusion flow path (4a), and in that the rubber extrusion device (<NUM>) further comprises
a control unit (<NUM>) for moving the die (<NUM>) and the head (<NUM>) to a desired relative position by controlling operation of the moving unit (<NUM>), and
a sensor (<NUM>) for detecting an amount of curving, with respect to an extrusion direction, of the rubber extrudate (R2) extruded from the extrusion port (<NUM>), and based on the detection data from the sensor (<NUM>), the control unit (<NUM>) is adapted for moving the die (<NUM>) and the head (<NUM>) to the desired relative position.