Abstract:
There is provided a thermocouple temperature detector mounting structure for a mixing tank for which the temperature detecting end of the thermocouple temperature detector mounted on the high viscosity mixing material mixer is capable of measuring temperature in real time and for which the mechanical load applied, by the flow of the material being mixed, on the temperature detecting end is made as small as possible. A temperature sensing portion with a hemispherical tip, of a protective inner tube that accommodates a thermocouple element of a thermocouple temperature detector, is mounted on a mixing tank, for mixing a high viscosity mixing material, so as to project from the end of a protective tip that projects into the mixing tank. With the outside diameter of a projecting base section of the protective tip that projects into the mixing tank being 2 to 3 times that of the protective inner tube, and with the projecting length (h) that projects into the mixing tank being the same length as the difference of the radius of the projecting base section of the protective tip and the radius of the protective inner tube, the outer circumferential face of a shoulder section of the protective tip, that is from the projecting base section of the protective tip to the site connecting to the outer circumference of the protective inner tube, is formed in a convex arcuate face that has a radius that is the difference of the radius of the projecting base section of the protective tip and the radius of the protective inner tube.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a thermocouple temperature detector mounting configuration for mounting a thermocouple temperature detector that detects temperature change of a kneading material with high sensitivity on a kneading tank of a closed pressure type kneader for kneading a high viscosity kneading material such as rubber, plastic and ceramics. 
       BACKGROUND ART 
       [0002]    In a known closed pressure type kneader for kneading a high viscosity kneading material such as rubber, plastic and ceramics, temperature of the kneading material which generate heat during a kneading operation is measured, for example, as disclosed in PTL 1, by providing a temperature detection end of the thermocouple temperature detector to extend from the bottom or side wall of the kneading tank for sensing the temperature of the kneading material which comes into contact with the temperature detection end. In kneaders having twin-shaft type kneading rotors which engagingly rotate in the kneading tank, lumpy or granular organic polymer materials having high viscosity is kneaded with compounding agent of inorganic substances having abrasiveness. Accordingly, a heavy rotation load is applied on the kneading material from the rotating kneading rotors of twin-shaft type, and a pressure load of the pressure lid is applied on the kneading material in order to prevent the kneading material from being uplifted in the kneading tank. The heat sensing section of the thermocouple element which is disposed on the temperature detection end of 
         [0000]    the thermocouple temperature detector is, therefore, housed in a protective tube made of a rigid material having a strength with abrasion resistance and impact resistance and is mounted on the bottom or side wall of the kneading tank. 
         [0003]    In the thermocouple element housed in the above-described protective tube, the temperature of the kneading material which varies according to the progress of kneading is transferred to the thermocouple element via the protective tube. Accordingly, in order to allow the measured temperature to follow the temperature change of the measurement target with high sensitivity, a grounding type is effective in which the distal end of the thermocouple element is welded to the distal end of the protective tube so that the temperature of the measurement target can be sensed by the outer surface of the protective tube and electromotive force generated by the thermocouple element is transmitted to a temperature display via a conductive wire. In this case, when the strength of the protective tube for bearing a load applied from the measurement target is sufficiently increased, the heat capacity of the protective tube increases. As a consequence, the thermocouple element does not always directly sense the temperature of the kneading material and is largely controlled by the temperature of the protective tube itself, and fails to follow the temperature change of the kneading material with high sensitivity. 
         [0004]    Further, when a rubber compound is kneaded in the kneading tank of the closed pressure type kneader, a loading rate of the kneading material including a compound agent to the kneading tank is 70 to 80% of the volume of the kneading tank to provide a flowing space for the kneading material in order to facilitate uniform distribution of the kneading material. Accordingly, the kneading material is not constantly in close contact with the detection end of the thermocouple temperature detector and is brought into contact with and moved away from the heat sensing section of the temperature detection end by engaging rotation of the twin-shaft type kneading rotors so as to dynamically moves in the flow space in the kneading tank not only in the rotation direction but also in the axis direction of the kneading rotor. As a consequence, the kneading material repeatedly comes into instantaneous contact with the temperature detection end, and the detection end fails to precisely sense the temperature of the kneading material during kneading without having a highly sensitive ability to follow the temperature. 
         [0005]    In spite of the recent high level of industrial technology, the closed pressure type kneader for high viscosity kneading material fails to display precise temperature values on the instrument due to the above problems and in most cases, displays only the measurement value which is lower than the actual temperature. This may be one of the causes of failure of preventing the variation of plasticity, which is one of the quality properties in a rubber kneading material of a small batch size. Further, the difference between the measured temperature and the actual temperature of the kneading material sacrifices recognition of the precise terminating point of kneading by temperature and precise temperature control automatic kneading which terminates kneading by setting the upper limit temperature. 
         [0006]    In order to overcome the above problems, in the thermocouple temperature detector disclosed in PTL 1, the shape and configuration of the protective tube which encloses the thermocouple element is improved so as to increase the sensitivity in an attempt to improve the accuracy of measured temperature. Since the protruding length of the detection end which protrudes into the kneading tank is formed large so that the thermocouple temperature detector does not lose heat sensitivity, a strength that can resist bending and breaking of the protective tube needs to be kept. As a result, the heat capacity of the protective tube increases, and the heat accumulation temperature effects to the measured temperature. This is not desirable for a parameter of kneading management. 
         [0007]    Further, in recent years, a high speed rotation rotor is provided in large-sized close type kneaders aiming the improvement of productivity, and various performances of kneading rotors having vane are improved. As there are many cases in which a large amount of kneading material having high hardness and abrasiveness is provided, there is a need of overcoming the problem of increasing the life length of protective tube without compromising the heat sensitivity of the temperature detection end. Further, in these cases, a mechanical load applied on the temperature detection end of the thermocouple temperature detector is substantially increased, and in addition to that, the load is more frequently applied on the protruding section of the temperature detection end in the front and back direction and in the right and left direction. As a result, the life length of the existing thermocouple temperature detectors tends to be substantially reduced. 
         [0008]    As described above, since a high speed and excessive energy is applied on the kneading material, it is inevitable that a load applied on the temperature detection end is increased compared with the conventional example. Since the temperature of the kneading material rapidly increases, the temperature needs to be precisely measured in real time. However, as the strength of protective tube is improved, the heat capacity is also increased, and this makes it difficult to perform real time measurement. Therefore, how the shape of protective tube is formed and how it is mounted on the kneading tank are important for performing precise temperature measurement while preventing bending or breaking of the detection end of the thermocouple temperature detector. 
       CITATION LIST 
     Patent Literature 
       [0009]    PTL 1: Japanese Unexamined Patent Application Publication No. 2012-21817 
       SUMMARY OF INVENTION 
     Technical Problem 
       [0010]    The technical subject of the present invention is to provide a mounting configuration of a thermocouple temperature detector on a kneader for high viscosity kneading material without increasing a mechanical strength which causes the increase of heat capacity of protective tube, so that a real time temperature measurement is possible and a mechanical load applied on the temperature detection end of the thermocouple temperature detector due to the flow of the kneading material by the kneading rotor is minimized as possible by the improvement in the shape of the distal end of the protective tube itself and the mounting configuration of the protective tube on the kneading tank. 
       Solution to Problem 
       [0011]    In order to solve the above problems, the present invention provides a mounting configuration of a thermocouple temperature detector for mounting the thermocouple temperature detector that measures a temperature of a high viscosity kneading material which is kneaded by rotation of a kneading rotor in a kneading tank of a closed pressure type kneader so that a heat sensing section is located in a flow area of the kneading material that flows along an inner surface of the kneading tank of the kneader, wherein the thermocouple temperature detector which is made up of two types of metal wires that generate a thermoelectromotive force is housed in a protective tube and is detachably mounted on the kneading tank, and the thermocouple temperature detector has a following configuration and is mounted on the kneading tank in the following mounting manner. 
         [0012]    That is, the protective tube of the thermocouple temperature detector is configured such that the heat sensing section of a hemispherical shape formed at a distal end of the protective inner tube protrudes from a center on a distal end of a short tubular shaped protective chip which has a shoulder at a distal end which protrudes in a flow area of the kneading material in the kneading tank, a protrusion proximal end of the protective chip which protrudes in the kneading tank has an outer diameter which is 2 to 3 times as large as that of the protective inner tube, a protruding length which protrudes from the protrusion proximal end into the kneading tank has the same length as the difference between a radius of the protrusion proximal end of the protective chip and a radius of the protective inner tube, an outer peripheral surface of the shoulder of the protective chip which extends from the protrusion proximal end of the protective chip to a position in the protruding length which is in contact with the outer periphery of the protective inner tube is formed in a convex curvature surface having a radius which corresponds to a difference between the radius of the protrusion proximal end of the protective chip and the radius of the protective inner tube. 
         [0013]    Further, the thermocouple element is made up of two types of metal wires, each one of ends of which is welded in a small hole formed at a tip of a protective inner tube so as to form the heat sensing section, and the other of ends of the two types of metal wires is led to the terminal board provided on the other end of the protective tube and housed in the protective tube, and the thermocouple temperature detector is mounted on the kneading tank such that the protrusion proximal end of the protective chip is located at a position along an inner surface of the kneading tank, the shoulder of the protective chip protrudes in the flow area of the kneading material so that a flow of the kneading material which flows along the inner surface of the kneading tank toward the temperature detection end is directed to a direction bypassing the protective chip, and a portion of the flow which flows toward the temperature detection end is directed to flow along the top of the heat sensing section which protrudes from the protective chip. 
         [0014]    As described above, when the protective inner tube that houses the metal wires of the thermocouple element of the thermocouple temperature detector is thickened to increase the strength, real time temperature measurement becomes difficult due to increase of heat capacity. Accordingly, in the thermocouple temperature detector of the present invention, the wall thickness of the heat sensing section of the protective inner tube is minimized as possible and the heat sensing section is facilitated to come into contact with the flowing kneading material to increase the heat transfer speed while preventing the heat sensing section from being subject to a load due to contact with the flowing kneading material. Specifically, the heat sensing section is formed in a hemispherical shape and is associated with the protective chip so that the kneading material flows along the top surface of the protective chip, thereby reducing a force applied from the kneading material. Accordingly, it is possible to prevent bending or breaking of a detection end of the thermocouple temperature detector and minimize as possible the wall thickness of the hemispherical shape on the distal end of the protective inner tube that forms the heat sensing section. 
         [0015]    Since the flow of the kneading material along the inner surface of the kneading tank during kneading causes the load of pressing and pulling stress in every direction around the temperature detection end to act on the temperature detection end, the protective chip located around the protective inner tube to protect the protective inner tube is formed such that the protrusion proximal end in the kneading tank has an outer diameter which is 2 to 3 times as large as that of the protective inner tube and has the wall thickness having a strength while being thermally insulated from the heat sensing section. In addition, the protruding length which protrudes from the protrusion proximal end into the kneading tank has a length which is the same length as the difference between a radius of the protrusion proximal end of the protective chip and a radius of the protective inner tube without having bending or breaking, and can be directly inserted in the inner wall of the kneading tank so as to be rigidly held, that is, the protective chip having the strength is disposed around the heat sensing section of the protective inner tube and protects the heat sensing section. Accordingly, the heat sensing section is sufficiently protected to provide the temperature detection end having a high temperature sensing precision. 
         [0016]    Further, according to the mounting configuration of the thermocouple temperature detector having the above mounting configuration, the temperature detection end is formed such that the protrusion proximal end of the protective chip in the temperature detection end of the thermocouple temperature detector is located at a position along the inner surface of the kneading tank and the proximal end of the hemispherical shape is located on the distal surface of the protective chip with only a minimal area of the shoulder of the protective chip and the hemispherical shape of the protective inner tube being located at the center of the distal end thereof protrude into the flow area of the kneading material. Accordingly, the temperature detection end is formed to protrude into the kneading tank while preventing the effect of a heavy rotation load applied on the kneading material from the kneading rotor from being directly loaded on the temperature detection end. 
         [0017]    That is, since the outer periphery of the shoulder of the protective chip is formed in a convex curvature that protrudes into the kneading tank, the flow of the kneading material along the inner surface of the kneading tank in any direction does not directly apply a load on the heat sensing section and is redirected at the shoulder of the protective chip formed in a convex curvature. A part of the kneading material which flows over the protective chip is directed to the distal surface of the heat sensing section which protrudes from the protective chip since there is an outer peripheral surface of a convex curvature shape at the shoulder of the protective chip. Accordingly, the distal surface of the heat sensing section is ensured to come into contact with the kneading material. However, a recess shape is formed around the contact area of the proximal end of the heat sensing section and the top surface of the protective chip and the area around the protrusion proximal end of the protective chip adjacent to the inner surface of the kneading tank, a gap is formed in the recess which is not in contact with the flowing kneading material. Even if the rubber kneading material having viscosity comes into contact with the heat sensing section and the shoulder of the protective chip, a load of the kneading material wound around the heat sensing section and the shoulder of the protective chip and pulled and pressed by the kneading rotor is reduced, thereby preventing a substantial bending force from being laterally applied. 
         [0018]    Further, as described above, the flow of the kneading material causes the load of pressing and pulling stress in every direction around the temperature detection end to act on the temperature detection end. Even if the flow of the kneading material having a particularly large vertical direction component impacts on the mounting position of the thermocouple temperature detector in the kneading tank, the flow of the kneading material having a large vertical direction component can be distributed to the around area since the convex curvature surface of the protective chip protrudes into the kneading tank and the heat sensing section of the protective inner tube is formed into a smooth hemispherical shape around of which is protected by the protective chip. Accordingly, as described above, the shape and mounting configuration of the protective chip for preventing a heavy load from being applied on the heat sensing section by the flow of the kneading material which flows to the temperature detection end along the inner surface of the kneading tank is important for protecting the heat sensing section. 
         [0019]    In a preferred embodiment of the mounting configuration of the thermocouple temperature detector of the present invention, the protective tube that is mounted on the kneading tank of the closed pressure type kneader includes the protective inner tube with an outer periphery except for the heat sensing section being covered by an insulating film tube having heat insulation property and two types of wires of the thermocouple element being inserted in the protective inner tube, and a sealing tube which is fitted around the protective tube with a space around the sealing tube, and the protective chip is mounted on the distal end of the sealing tube, the protective chip being formed in a cylindrical shape that protrudes from the inner surface of the kneading tank into the kneading tank, with a mounting hole being formed in the protective chip so that the heat sensing section at the distal end of the protective inner tube is inserted therethrough via the insulation film tube. 
         [0020]    In another preferred embodiment of the present invention, the kneading tank includes a pair of rotor chambers having a cylindrical shape and connected to each other with their axis lines being horizontally arranged side by side so that the rotor chambers communicate with each other, in which a kneading rotor having a plurality of blades on the outer periphery is rotatably disposed in each rotor chamber spaced from an inner peripheral surface of the rotor chamber, and the kneading rotor is configured to downwardly rotate in the rotor chamber on a communicating side of the rotor chambers, and the temperature detection end of the thermocouple temperature detector protrudes from a top surface of a ridge wall which raises in a chevron shape at the bottom of a boundary between the rotor chambers. 
       Advantageous Effects of Invention 
       [0021]    According to the mounting configuration of the thermocouple temperature detector of the present invention which is above described in detail, a real time temperature measurement can be achieved without increasing a mechanical strength of the protective tube of the thermocouple temperature detector which increases the heat capacity of the protective tube. In addition, the shape of the distal end of the protective tube itself and the mounting configuration to the kneading tank are improved so that the mechanical load applied on the temperature detection end of the thermocouple temperature detector due to flow of the kneading material by the kneading rotor can be minimized as possible. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0022]      FIG. 1  is a vertical sectional view which shows an essential part of an embodiment for mounting a thermocouple temperature detector on a kneading tank of a closed pressure type kneader of tank inversion discharging type with a mounting configuration according to the present invention. 
           [0023]      FIG. 2  is a vertical sectional view which shows an essential part of an embodiment for mounting a thermocouple temperature detector on a kneading tank of a closed pressure type kneader of bottom opening discharging type with a mounting configuration according to the present invention. 
           [0024]      FIG. 3  is a vertical sectional view which shows a configuration example of the thermocouple temperature detector. 
           [0025]      FIG. 4  is a partial enlarged sectional view which shows a configuration of an essential part of the thermocouple temperature detector. 
           [0026]      FIG. 5  is a schematic explanatory view of an essential part of a cross section at the same position as that of  FIG. 1  and  FIG. 3  which show kneading of a kneading material in a kneading tank on which the thermocouple temperature detector is mounted. 
           [0027]      FIG. 6  is a schematic explanatory view of an essential part of a cross section along a ridge wall between rotor chambers which shows kneading of a kneading material in a kneading tank on which the thermocouple temperature detector is mounted. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0028]      FIG. 1  shows an example of configuration for mounting a thermocouple temperature detector on a kneading tank of a relatively small-sized closed pressure type kneader for high viscosity kneading material of a tank inversion discharging type according to the present invention. The closed pressure type kneader of tank inversion discharging type is a known device which is commonly used for kneading a high viscosity kneading material such as rubber, plastic and ceramics, and the general configuration thereof will be briefly described below. The closed pressure type kneader of tank inversion discharging type is configured to discharge a kneading material by inverting the kneading tank about a rotation shaft of one of a pair of kneading rotors  8 A,  8 B, which will be described later, after completion of kneading in the kneading tank. 
         [0029]    First, the kneading tank  1  shown in the figure which forms an essential part of the closed pressure type kneader is located in the lower part of the kneader body, and a pair of rotor chambers  3 A,  3 B having the identical cylindrical shape are disposed in the kneading tank  1  and are symmetrically connected to each other with their axis lines being arranged horizontally parallel side by side so that the rotor chambers  3 A,  3 B communicate with each other. A ridge wall  4  which protrudes in a chevron shape is formed on an inner bottom of the kneading tank  1  at the boundary of inner peripheral surfaces of the rotor chambers  3 A,  3 B, and both end faces of the rotor chambers  3 A,  3 B in an axis direction are closed by end walls of the tank. Further, the rotor chambers  3 A,  3 B have the cross section which is uniform in the axis direction. 
         [0030]    Kneading rotors  8 A,  8 B for kneading a high viscosity kneading material loaded in the tank are rotatably supported by the end walls of the tank and are disposed in the rotor chambers  3 A,  3 B, respectively. The kneading rotors  8 A,  8 B are rotatably disposed spaced from the inner peripheral surfaces of the rotor chambers  3 A,  3 B. The kneading rotors  8 A,  8 B of twin-shaft type in the kneading tank  1  are provided with a plurality of spiral blades  9  on the outer peripheral. The kneading rotors  8 A,  8 B are connected to a driving source so that the blades  9  of the kneading rotors  8 A,  8 B downwardly rotate on the communicating side of the rotor chambers  3 A,  3 B and the blades  9  of the kneading rotors  8 A,  8 B also alternatively rotate. The kneading rotors  8 A,  8 B may rotate at the same rotating speed or at a slightly different speeds. The blades  9  are not necessarily limited to two blades. 
         [0031]    The kneading tank  1  has an opening  5  on the top surface for loading and unloading the kneading material into and out of the tank, and the opening  5  is closed by a pressure lid  6 . However, in the kneading tank  1 , the pressure lid  6  may be uplifted by the kneading material due to a heavy rotation load applied on the kneading material from the two rotating shafts of the kneading rotors  8 A,  8 B, or a pressure in the kneading tank  1  increased with increase of temperature of the kneading material as the kneading operation proceeds. For this reason, the pressure lid  6  of the kneading tank  1  is connected to a lower end of a rod  7  of a hydraulic cylinder (which is not shown in the figure) which is disposed in the upper part of the kneader body so that the opening  5  is opened and closed by upward and downward movement of the rod  7 . Accordingly, when the kneading material is loaded and unloaded into and from the kneading tank  1  via the opening on the top surface of the kneading tank  1  and the pressure lid  6  is closed, the kneading material is kneaded by the spiral blades  9  in a complicated flow direction including the rotation direction and the axis direction of the rotors by rotating the two rotors  8 A,  8 B while pressurizing the kneading material by using the pressure lid  6 . 
         [0032]    While the closed pressure type kneader of  FIG. 1  is a tank inversion discharging type,  FIG. 2  shows an example of configuration of mounting a thermocouple temperature detector  10  according to the present invention on the kneading tank  2  of a large-sized closed pressure type kneader of bottom opening discharging type which is suitable for mass manufacturing of tires or the like. This closed pressure type kneader of bottom opening discharging type is also a known device which is commonly used as well as the above described tank inversion discharging type kneader. Compared with the tank inversion discharging type kneader, the closed pressure type kneader of bottom opening discharging type is configured such that the bottom of the kneading tank  2  is openable by a discharge door  2   a  which is mounted via a hinge  2   b , the discharge door  2   a  can be locked into a closed state by using a latch  2   d  which is advanced and retracted by a hydraulic cylinder  2   c , and the thermocouple temperature detector  10  is mounted on the discharge door  2   a  in the same manner as in the case of the closed pressure type kneader of tank inversion discharging type shown in  FIG. 1 . In this pressurizing type kneader of bottom opening discharging type, since the temperature detector  10  is mounted on the openable discharge door  2   a  at the bottom of the kneading tank  2 , a maintenance operation and the like of the thermocouple temperature detector  10  can be easily performed compared with the closed pressure type kneader of tank inversion discharging type. 
         [0033]    The closed pressure type kneader of bottom opening discharging type is configured such that the discharge door  2   a  at the bottom of the kneading tank  2  is opened after completion of kneading by the rotors  8 A,  8 B of the kneading tank  2  to discharge the kneading material. Although it is partially different from the closed pressure type kneader of tank inversion discharging type of  FIG. 1  in that, for example, the opening  5  is formed small so as to prevent the kneading material from being discharged from the top surface, the remaining configuration and effect are the same as those of the closed pressure type kneader of tank inversion discharging type shown in  FIG. 1  and  FIGS. 3 to 6 . Therefore, their description is incorporated herein, and main corresponding parts are denoted by the same reference numbers and the detailed description thereof are omitted. 
         [0034]    In the closed pressure type kneader, the thermocouple temperature detector  10  that measures the temperature of the high viscosity kneading material which is kneaded by rotation of the kneading rotors  8 A,  8 B in real time as possible has a configuration as described below with reference to  FIGS. 3 and 4 . The thermocouple temperature detector  10  is detachably attached on the kneading tank  1  so that a temperature detection end  10   a  of the thermocouple temperature detector  10  is located in a flowing area of the kneading material which flows along the inner wall surface of the kneading tank  1 . In the example shown in  FIGS. 1 and 2 , the thermocouple temperature detector  10  is threadingly inserted from the lower part on the outer surface of the kneading tank  1  to be removably attached thereto so that the temperature detection end  10   a  of the thermocouple temperature detector  10  extends from the top surface of the ridge wall  4  formed at the boundary of the inner peripheral surfaces of the rotor chambers  3 A,  3 B. 
         [0035]    Brief description of a kneading operation of the closed type kneader for high viscosity kneading material will be described by an example of kneading a high viscosity rubber compound. Usually, approximately 75% of a space volume of the kneading tank  1  subtracted by the volume of two rotating kneading rotors  8 A,  8 B is a net volume for kneading the kneading material. When a rubber compound of 100% of the space volume is loaded, the kneading material is wound around the two rotating kneading rotors  8 A,  8 B and rotates in a cylindrical shape during kneading, and the loaded kneading material is not distributed. When a suitable amount of the material is loaded, kneading operation starts with crushing of polymer (raw material rubber) into pieces in the powder material. Then, as the powder material is kneaded into the polymer and small granules are generated, the temperature of the kneading material increases, and accordingly, the rubber kneading material becomes viscous and a large lump of the kneading material is generated in the kneading tank  1 . This increase a load applied on the temperature detection end  10   a  which protrudes into the kneading tank  1 . Since a space volume of 20 to 30% is left in the kneading tank  1 , the kneading material freely moves across the tank at high speed in response to rotation of the kneading rotors  8 A,  8 B. Only when the kneading material comes into contact with the temperature detection end  10   a  (a heat sensing section  18  which will be described later) of the thermocouple temperature detector  10 , the temperature detector  10  instantaneously senses the temperature and outputs them as the time course temperature data. 
         [0036]    Next, a configuration of the thermocouple temperature detector  10  used in the closed type kneader will be described in detail. The thermocouple temperature detector  10  includes a thermocouple element  12  made up of two types of metal wires  12   a ,  12   b  which generate a thermoelectromotive force due to Seebeck effect, and the thermocouple element  12  is housed in a protective tube  14  for protection. The protective tube  14  includes a sealing tube  15  which forms a sheath of the thermocouple temperature detector  10 , and a protective inner tube  17  in which the metal wires  12   a ,  12   b  which form the thermocouple element  12  are inserted. The distal end of the sealing tube  15  is connected to a protective chip  16 , which will be described later, and the outer periphery of the protective inner tube  17  except for a heat sensing section  18  formed in a hemispherical shape at the distal end is covered by a heat insulating film tube  19  having heat insulating property and electric insulating property. 
         [0037]    In the thermocouple temperature detector  10 , the thermocouple element  12  having a temperature detection function is welded to each one of the ends of the metal wires  12   a ,  12   b  which generate a thermoelectromotive force. The welded section is inserted in a small hole  17   a  formed at the tip end of the hemispherical protective inner tube  17  and is welded at the distal end of the protective inner tube  17  by build-up welding from the outside of the protective inner tube  17  so as to be fixed to the protective inner tube  17  in a grounded state to form the heat sensing section  18 . Then, two types of metal wires  12   a ,  12   b  are each covered by an insulation cover  13  that prevents electrical contact and are inserted in the protective inner tube  17 . The other of the ends of the metal wires  12   a ,  12   b  are led to a terminal board  24  and connected thereto. The terminal board  24  is disposed in a detector body  21  and is provided via a mounting fixture  22  for mounting on the kneading tank  1  at the other end of the protective tube  14 . The metal wires  12   a ,  12   b  of the thermocouple element  12  connected to the terminal board  24  are led out to the outside of the detector body  21  via conductive wires and are connected to various instrument so that the temperature of the kneading material is displayed as the value of temperature based on the thermoelectromotive force or is used as a control signal. 
         [0038]    As described above, the protective tube  14  includes the sealing tube  15  and the protective inner tube  17  in which the thermocouple element  12  is inserted. The sealing tube  15  is fitted around the protective inner tube  17  with a space  20  being interposed between the sealing tube  15  and the outer periphery of the protective inner tube  17  for heat insulation so as to be provided as a sheath of the protective tube  14 . The protective chip  16  of a cylindrical shape is fixed to the distal end of the protective tube  14  so as to protrude from the inner wall surface of the kneading tank  1  into the flow area of the kneading material in the kneading tank  1 . A mounting hole  16   c  is formed in the protective chip  16  so that the distal end of the protective inner tube  17  is inserted through the mounting hole  16   c  via the heat insulation film tube  19 , and the heat sensing section  18  formed in a hemispherical shape at the distal end of the protective inner tube  17  protrudes from the distal end of the protective chip  16  through the mounting hole  16   c.    
         [0039]    In the configuration for mounting the thermocouple temperature detector  10  on the kneading tank  1 , a detector mounting hole  1   a  is formed at a mounting position of the temperature detector  10  in the kneading tank  1  so that the protective chip  16  is closely fitted in the detector mounting hole  1   a  and a portion of the protective chip  16  from a protrusion proximal end  16   a  which is located on the inner wall surface of the kneading tank  1  to the temperature detection end  10   a  at the distal end protrudes in the flow area of the kneading material. The length of the temperature detection end  10   a  protruding into the kneading tank  1  is determined by threading the mounting fixture  22  into the detector mounting hole  1   a  and fixed thereto along with the “tank body”. The mounting configuration of the thermocouple temperature detector  10  is not limited to the above described threading insertion. A flange may be formed on the mounting fixture  22  or the like and fixes it to the outer surface of the kneading tank by using bolts. 
         [0040]    The protective chip  16  of the thermocouple temperature detector  10  which is mounted on the kneading tank  1  has an outer diameter at the protrusion proximal end  16   a  which is at the proximal end protruding from the inner wall surface of the kneading tank  1  which is 2 to 3 times as large as that of the protective inner tube  17 . As shown in  FIG. 4 , a protruding length h which protrudes from the protrusion proximal end  16   a  into the kneading tank  1  has the same length as the difference between the radius of the outer circumference of the protrusion proximal end  16   a  of the protective chip  16  and the radius of the protective inner tube  17  at the protrusion proximal end  16   a , and, the outer peripheral surface of a shoulder  16   b  of the protective chip  16  which extends from the protrusion proximal end  16   a  of the protective chip  16  to a position p in the protruding length h which is in contact with the outer periphery of the protective inner tube  17  is formed in a convex curvature surface having a radius which corresponds to the difference between the radius of the protrusion proximal end  16   a  of the protective chip  16  and the radius of the protective inner tube  17 . 
         [0041]    When the protective chip  16  of the thermocouple temperature detector  10  is positioned as described above, the temperature detection end  10   a  of the protective chip  16  protrudes into the flow area of the kneading material as shown in  FIGS. 5 and 6 . As will be described below with reference to  FIGS. 5 and 6 , the load applied on the temperature detection end  10   a  and the heat sensing section  18  of the protective inner tube  17  from the kneading material can be substantially small due to the presence of the temperature detection end  10   a  and the related configuration of the heat sensing section  18  of the protective inner tube  17  to the temperature detection end  10   a.    
         [0042]    Particularly, since there is the heat insulation film tube  19  between the protective chip  16  and the protective inner tube  17 , the heat capacity seldom effects to the real-time temperature detection. Accordingly, it is easy to provide strength to bear the load applied from the kneading material by thickening the wall. As a result, the protective chip  16  is effective for reducing the load applied on the heat sensing section  18  of the protective inner tube  17  from the kneading material. Further, when the protective tube  14  is mounted on the kneading tank  1 , a ventilation hole is formed on the sealing tube  15  so that the gap  20  between the protective inner tube  17  and the sealing tube  15  communicates with the outside to prevent the heat stored in the kneading tank  1  from being transferred to the temperature detection end  10   a . The heat insulation film tube  19  is provided not only for preventing heat transfer, but also for preventing leakage of a weak electromotive force supplied from the thermocouple element  12  through the protective tube  14  into the kneading tank  1  and for protecting it from the adverse effect by electricity of the kneading tank  1 . 
         [0043]    Since the kneading material freely moves across the flow space in the kneading tank by rotation of the kneading rotors  8 A,  8 B of the kneading tank  1  and a substantial impact load is repeatedly applied on the temperature detection end  10   a , the load of pressing and pulling stress in every direction around the temperature detection end  10   a  acts on the temperature detection end  10   a  which protrudes into the kneading tank  1 . The flow of the kneading material which flows toward the position of the temperature detection end  10   a  is roughly divided into two types of flow in terms of the direction of the load applied on the temperature detection end  10   a , that is, a flow which mainly flows to the temperature detection end  10   a  so as to press it downward (in the axis direction of the temperature detector  10 ) as shown in  FIGS. 1 and 5  (first flow), and a flow which mainly flows along the inner surface of the kneading tank  1  at the position of the temperature detection end  10   a  and is largely inclined to the axis direction of the temperature detector  10  so as to flow from one side of the temperature detection end  10   a  to the other side as shown in  FIGS. 5 and 6  (second flow). 
         [0044]    The first flow is, for example, a flow by which the kneading material located at the center portion of the kneading tank  1  in which the rotor chambers  3 A,  3 B communicate to each other is directed to the temperature detection end  10   a  in the kneading tank  1  at the center portion by downward rotation of the blade  9  of either of the kneading rotors  8 A,  8 B, or a flow by which the kneading material which follows the blade  9  downwardly presses the temperature detection end  10   a  when the blade  9  rotates under the ridge wall  4  of the kneading tank  1 . Further, the second flow is generated by a flow of the kneading material along the inner surface of the rotor chambers  3 A,  3 B which occurs mainly by rotation of the kneading material in the rotor chambers  3 A,  3 B in response to rotation of the kneading rotors  8 A,  8 B. It is necessary to minimize the load applied on the heat sensing section  18  from the above flow, and this need is accommodated by combination shaped of the hemispherical shape of the distal end of the heat sensing section  18  and the protective chip  16 . 
         [0045]    In general, the first flow and the second flow in a combined state come into contact with the surface of the temperature detection end  10   a  while passing by the temperature detection end  10   a . On this assumption, the temperature detection end  10   a  needs to have a sufficient strength to bear the load applied by the combined flow. Since the kneading material does not impact on the temperature detection end  10   a  with an inertia force in the initial phase of kneading in which crushed pieces of the kneading material are mixed, the load applied on the heat sensing section  18  from the kneading material is not particularly large. On the other hand, in the phase in which the kneading material becomes viscous and a large lump of the kneading material is generated in the kneading tank  1 , the load of pulling stress due to sticking and winding of the kneading material is frequently applied on the temperature detection end  10   a  which extends into the kneading tank  1  starts to increase as the kneading rotors  8 A,  8 B rotate. Accordingly, for the temperature detection end  10   a , reduction of the load applied on the temperature detection end  10   a  in a direction orthogonal to the axis direction is mainly considered in this phase. 
         [0046]    The load due to the first and second flow of the kneading material which is applied on the temperature detection end  10   a  will be described below in detail. First, when the flow of the kneading material flowing to the temperature detection end  10   a  in the kneading tank  1  is the first flow, the flow mainly impacts on the front side of the temperature detection end  10   a , that is, the protective chip  16  and the heat sensing section  18  at the center of the protective chip  16 . Since the shoulder  16   b  of the protective chip  16  has the protruding length h which protrudes into the kneading tank  1  which is the same as the thickness in the radial direction and the outer peripheral surface which is formed as a convex curvature surface which protrudes into the kneading tank  1 , and the heat sensing section  18  of the protective inner tube  17  is held by the protective chip  16  at the periphery and has a protruding section formed in a hemispherical shape, the flow of the kneading material is distributed to the surrounding area along the outer surface of the heat sensing section  18  of a hemispherical shape and the shoulder  16   b  of the protective chip  16  of a convex curvature surface. As a result, even if the first flow impacts on the temperature detection end  10   a  in the axis direction, the flow is distributed to the surrounding area while pressing down the heat sensing section  18  of a hemispherical shape. Accordingly, the heat sensing section  18  may only have a strength necessary to bear the distribution of the flow, and is not subject to a severe damage. 
         [0047]    On the other hand, when the flow of the kneading material flowing to the temperature detection end  10   a  in the kneading tank  1  is the second flow, the flow presses against the lateral side of the temperature detection end  10   a  while flowing along the inner surface of the kneading tank  1  and may cause the heat sensing section  18  to be inclined or broken, and this flow may be the main cause of damaging the temperature detection end  10   a . More specifically, the second flow is a case where the kneading material having flowing viscosity is pulled in the arrow C direction while following the rotation of the blade  9  of the kneading rotor  8 B in the kneading tank  1  as schematically shown in  FIG. 5 , or where the kneading material having increased flowing viscosity flows along the ridge wall  4  between the rotor chambers  3 A,  3 B as shown in  FIG. 6 . As a matter of course, the kneading material located at the center portion in which the rotor chambers  3 A,  3 B communicate with each other flows to the position of the temperature detection end  10   a  on the ridge wall  4  in the kneading tank  1  at the center portion by downward rotation of the blade  9  of either of the kneading rotors  8 A,  8 B. In this flow of the kneading material, when a component of the second flow is large, it is substantially the same as the case of  FIG. 5  in which the kneading material follows the blade  9 , and, when the kneading material mainly flows downward to the temperature detection end  10   a , the flow is the first flow. 
         [0048]    In the configuration of the temperature detection end  10   a  for performing a sufficient strength to bear the load applied by the second flow, the heat sensing section  18  having a hemispherical shape formed on the distal end of the protective inner tube  17  protrudes from the distal end of the protective chip  16 , the protruding length h protrudes from the protrusion proximal end  16   a  of the protective chip  16  into the kneading tank  1  has the same length as the difference between the radius of the protrusion proximal end  16   a  of the protective chip and the protective inner tube  17 , and the outer peripheral surface of the shoulder  16   b  of the protective chip  16  is formed in a convex curvature surface having a radius which corresponds to the difference between the radius of the protrusion proximal end  16   a  of the protective chip  16  and the protective inner tube  17 . Since the kneading material having viscosity which flows toward the temperature detection end  10   a  in the state shown in  FIG. 5  follows the blade  9  of the kneading rotor  8 B and is pulled in the arrow C direction, it reaches the heat sensing section  18 . However, as described below, the flow of the kneading material flows along the top surface of the heat sensing section  18  and is basically directed in the direction which substantially bypasses the temperature detection end  10   a  which includes the heat sensing section  18 . As a result, a large flowing load of the kneading material is not applied on the heat sensing section  18  of the protective inner tube  17 . 
         [0049]    More specifically, since the outer periphery of the shoulder  16   b  of the protective chip  16  is formed in a ring shape of a smooth convex curvature surface and holds the protective inner tube  17  and has a high strength, a portion of the kneading material flowing in the arrow C direction which is directed to the protective chip  16  becomes a bypassing flow by flowing around or over the protective chip  16 . Particularly, on the side of the temperature detection end  10   a  which faces the rotor chamber  3 A, since there is a flow of the kneading material in the arrow D which follows the blade  9  of the kneading rotor  8 A in the rotor chamber  3 A, the kneading material tends to be pulled by the flow and flows into the rotor chamber  3 A. As a result, the flow in the direction of the arrow C which applies a large pressing force on the side of the heat sensing section  18  which faces the rotor chamber  3 A is not generated, and the flow is rather similar to the first flow. Although there may be a bypassing flow in the direction of the arrow C which flows in the direction that flows over the protective chip  16 , the flow flows along the top surface of the heat sensing section  18  of the protective chip  16  and then flows along the inner surface of the rotor chamber  3 B. 
         [0050]    As described above, the flow of the kneading material which is pulled by rotation of the kneading rotor  8 B and flows in the direction of the arrow C of  FIG. 5  does not always flow along the top surface of the heat sensing section  18  after flowing over the protective chip  16 . Although the flow may intermittently impact on the temperature detection end  10   a  from a space formed in the kneading tank  1  on a temporary basis, such a flow has little risk of applying a large load on the heat sensing section  18 . Usually, as shown in  FIG. 5 , the normal flow of the kneading material flows along and over the top surface of the hemispherical heat sensing section  18 , and then, again comes into contact with the outer peripheral surface of the shoulder  16   b  of the protective chip  16  formed in a convex curvature surface. Further, the kneading material which flows over the outer peripheral surface having a convex curvature surface comes into contact with the inner surface of the kneading tank  1  having raised outer peripheral surface, the kneading material does not flow into the recess  26   a  between the heat sensing section  18  and the outer peripheral surface of a convex curvature surface of the shoulder  16   b  of the protective chip  16  and a recess  26   b  between the outer peripheral surface of the protective chip  16  and the inner surface of the kneading tank  1  at which the protective chip  16  raises, that is, lumps of the kneading material do not stick on the heat sensing section  18  or the temperature detection end  10   a  and do not apply a large load by being in contact with the heat sensing section  18  or the temperature detection end  10   a.    
         [0051]    Similarly, in the kneading material which flows in the direction shown in  FIG. 6 , the kneading material which normally flows in the arrow E direction along the ridge wall  4  becomes a bypassing flow which flows around or over the protective chip  16  at a point which is in contact with the outer peripheral surface of a convex curvature surface of a ring-shaped shoulder  16   b  of the protective chip  16 . The kneading material flowing in the direction over the protective chip  16  reaches the heat sensing section  18  along the outer periphery of the shoulder  16   b  of the convex curvature surface, but does not flow into the recess  26   a  between the outer peripheral surface of a convex curvature surface of the protective chip  16  and the heat sensing section  18 . After flowing along and over the top surface of the heat sensing section  18 , it again comes into contact with the outer peripheral surface of the shoulder of the protective chip  16  of the convex curvature surface. The kneading material which flows over the outer peripheral surface of the convex curvature surface comes into contact with the inner surface of the kneading tank  1  at which the outer peripheral surface raises, and does not flow into the recess  26   a  between the outer peripheral surface of a convex curvature surface of the protective chip  16  and the heat sensing section  18  or the recess  26   b  between the outer peripheral surface of the protective chip  16  and the inner surface of the kneading tank  1  at which the protective chip  16  raises, that is, lumps of the kneading material are wound around or sticks on the heat sensing section  18  due to the presence of the outer peripheral surface of the convex curvature surface of the shoulder  16   b  of the protective chip  16  and do not apply a large flowing load by being in contact with the heat sensing section  18 . 
         [0052]    As described above, the kneading material which is kneaded by the kneading rotors  8 A,  8 B in the kneading tank and is directed to the temperature detection end  10   a  as the second flow comes into strong contact with the outer peripheral surface of the convex curvature surface of the shoulder  16   b  of the protective chip  16 , but is forced to bypass by the convex curvature surface to move along the heat sensing section  18  of the hemispherical shape at the distal end of the protective inner tube  17 , and does not apply a load on the protective inner tube  17  in a direction of inclining the protective inner tube  17 , and is ensured to come into contact with the heat sensing section  18  so that the instantaneous temperature can be detected. Further, since the protective chip  16  itself also has the outer peripheral surface formed in a convex curvature surface and only a distal portion of the protrusion from proximal end  16   a  protrudes in the kneading tank  1 , the flowing load applied on the protective chip  16  can be reduced. Even if the flowing load from the kneading material of some extent is applied, the stress load is reduced by the flow of the kneading material being appropriately guided. 
       REFERENCE SIGNS LIST 
       [0000]    
       
         
           
               1 ,  2  kneading tank 
               1   a  detector mounting hole 
               3 A,  3 B rotor chamber 
               4  ridge wall 
               5  opening 
               6  pressure lid 
               7  rod 
               8 A,  8 B kneading rotor 
               9  blade 
               10  thermocouple temperature detector 
               10   a  temperature detection end 
               12  thermocouple element 
               12   a ,  12   b  metal wire 
               13  insulation cover 
               14  protective tube 
               15  sealing tube 
               16  protective chip 
               16   a  protrusion proximal end 
               16   b  shoulder 
               16   c  mounting hole 
               17  protective inner tube 
               17   a  small hole 
               18  heat sensing section 
               19  heat insulation film tube 
               20  gap 
               21  detector body 
               22  mounting fixture 
               24  terminal board 
               26   a ,  26   b  recess