JP2011110884A - Temperature control structure of extrusion molding die - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a temperature control structure of an extrusion molding die that can satisfactorily perform extrusion molding using every thermoplastic resin as a raw material and stabilize the quality of a seamless product. <P>SOLUTION: The temperature control structure 11 of the extrusion molding die includes an insertion hole 13 penetrating a core 1 in its axial direction; an inner heater 15 provided at the core 1; an inside mandrel 17 regulating the radial contraction of thermoplastic resin extruded from a clearance 31; a refrigerant introducing pipe 19 inserted through the insertion hole 13 of the core 1 to introduce a refrigerant into the inside mandrel 17; and an outer heater 21 provided at a die 7. The inner heater 15 is arranged around the refrigerant introducing pipe 19 through a void 35. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a temperature control structure of an extrusion mold for molding a thermoplastic resin so as to become a tubular seamless (seamless) product.

  Patent Documents 1 and 2 disclose an extrusion mold for producing a seamless product. A heater is attached to the mandrel or die body of the extrusion mold, and the raw material supplied between the mandrel and the die body is heated by the heat of these heaters. For example, when extrusion molding is performed using a polyolefin-based resin such as polyethylene or polypropylene as a raw material, the heating temperature of the heater is set so that the temperature of the raw material is about 220 ° C.

  If the raw material is a fluororesin, the heating temperature of the heater is set to about 450 ° C. This temperature is close to the upper limit of the heating temperature of the heater using Joule heat as a heat source, but if it falls below 450 ° C., the fluidity of the fluororesin is impaired. Since such a high-temperature resin has a relatively large shrinkage rate in the process of being cooled, the dimensions of the seamless product are likely to be distorted.

  Therefore, as shown in Patent Document 3, the end of the mandrel extends outward from the die body, and the inner peripheral surface of the seamless product immediately after being extruded from the die body presses against the outer peripheral surface of the end of the mandrel. Like that. Thereby, it is possible to restrict the seamless product from shrinking in the radial direction, and to improve the finish of the inner peripheral surface of the seamless product. Furthermore, cooling water is introduced into the end of the mandrel so that the temperature at the end of the mandrel is relatively low. As a result, cooling of the seamless product is promoted, and it is possible to prevent the seamless product from further contracting after being detached from the end of the mandrel.

  However, since the mandrel conducts the heat of the heater and releases it to the cooling water, the output of the heater must be increased. Such heat conduction increases the tendency of the overall temperature of the mandrel to be uniform, making it difficult to control the temperature at the end of the mandrel.

JP 2002-331570 A Japanese Patent Laid-Open No. 6-91731 JP-A 52-107057

  An object of the present invention is to provide a temperature control structure of an extrusion mold that can satisfactorily perform extrusion molding using any thermoplastic resin as a raw material and can stabilize the quality of a seamless product.

  In order to achieve the above object, the present invention joins an axial core to a mandrel, and a die body into which the mandrel is inserted, a die that forms a gap around the core, and the mandrel and the die body. A temperature control structure of an extrusion mold for forming a cylindrical shape by extruding a thermoplastic resin supplied between the core and the core, an insertion hole penetrating the core in an axial direction thereof, and the core An inner heater provided on the inner mandrel, an inner mandrel that restricts radial shrinkage of the thermoplastic resin extruded from the gap, a refrigerant introduction pipe that is inserted into the insertion hole of the core and introduces a refrigerant into the inner mandrel, and the die And the inner heater is disposed around the refrigerant introduction pipe with a gap interposed between the inner heater and the outer heater.

  Further, the present invention is characterized in that the inside mandrel is supported by the refrigerant introduction pipe at a position sandwiching a gap with respect to the core, and is fitted inside a cylindrical thermoplastic resin extruded from the gap. To do.

  Further, the present invention is characterized in that the refrigerant introduction pipe is connected to the core via a spacer that secures a gap around the refrigerant introduction pipe.

  In the present invention, the spacer includes an annular portion that fits into the insertion hole and allows the refrigerant introduction tube to pass inside, and a tooth shape portion that protrudes toward the inside of the annular portion and sandwiches the refrigerant introduction tube. It is characterized by providing.

  Further, according to the present invention, the inside mandrel has a cold storage chamber for introducing a refrigerant, and the refrigerant introduction pipe has a feed pipe through which the refrigerant supplied to the cold storage chamber passes, and the refrigerant discharged from the cold storage chamber. It is a double pipe inserted inside the return pipe to be passed.

  Further, the present invention is characterized in that the refrigerant introduction pipe is shielded from the inner heater by a heat insulating material.

  In the temperature control structure of the extrusion mold according to the present invention, a refrigerant introduction tube is inserted into an insertion hole that penetrates the axial direction of the core, and an inner heater that heats the core is disposed around the refrigerant introduction tube via a gap. Yes. For this reason, the heat of the inner heater and the outer heater that respectively heat the core and the die can be blocked by the air gap from being conducted from the refrigerant introduction pipe to the inside mandrel.

  Therefore, according to the temperature control structure, it is possible to prevent heat from escaping from the core to the refrigerant introduced into the refrigerant introduction pipe, so that the thermosetting resin that is a raw material of the seamless product is effectively heated by the inner heater and the outer heater. Can do. Moreover, the temperature of the inside mandrel is not affected by the heat of the inner heater and the outer heater. For this reason, regardless of the heat generation temperature of the inner heater and the outer heater set to ensure good fluidity of the thermosetting resin, the temperature control structure allows seamless products made from any thermosetting resin as a raw material. Can be manufactured with stable quality.

  Furthermore, according to the temperature control structure of the extrusion mold according to the present invention, the inside mandrel is supported by the refrigerant introduction pipe at a position where the gap is sandwiched with respect to the core, so that the inside mandrel is directly connected to the core. Both can be insulated by air gaps. For this reason, the inside mandrel can be cooled to a desired temperature irrespective of the temperature of the inside mandrel.

  Furthermore, according to the temperature control structure of the extrusion mold according to the present invention, the annular portion of the spacer that secures a gap around the medium introduction tube is fitted into the insertion hole of the core and protrudes toward the inside of the annular portion. Since the refrigerant introduction tube is sandwiched between the tooth profile portions, the area where the spacer contacts the refrigerant introduction tube can be reduced. Thereby, it can suppress that the heat of an inner heater and an outer heater is conducted to a refrigerant | coolant inlet tube via a spacer.

  In the temperature control structure of the extrusion mold according to the present invention, the refrigerant introduction pipe receives a certain amount of radiant heat from the inner heater, but the refrigerant introduction pipe is a double pipe inserted through the return pipe inside the return pipe. The radiant heat can be absorbed by the refrigerant discharged from the cold storage chamber of the inside mandrel to the return pipe. For this reason, the said temperature control structure has the advantage that the refrigerant | coolant supplied to a cool storage chamber through a feed pipe is not heated unnecessarily.

  Furthermore, according to the temperature control structure of the extrusion mold according to the present invention, since the refrigerant introduction pipe is shielded from the inner heater by the heat insulating material, there is an advantage that the refrigerant is not unnecessarily heated by the radiant heat from the inner heater.

Sectional drawing of the axial direction of the temperature control structure of the extrusion mold which concerns on embodiment of this invention. Sectional drawing which fractured | ruptured the temperature control structure of the extrusion mold which concerns on embodiment of this invention by the AA line of FIG. Sectional drawing which fractured | ruptured the waist part of the temperature control structure of the extrusion die concerning embodiment of this invention in the position which crosses the core to radial direction. Sectional drawing which shows the modification of the waist | hip | lumbar part of the temperature control structure of the extrusion mold which concerns on embodiment of this invention. Sectional drawing which shows the further modification of the waist part of the temperature control structure of the extrusion die which concerns on embodiment of this invention. (A) is a top view which shows the modification of the spacer applied to the extrusion die which concerns on embodiment of this invention, (b) is the sectional drawing. (A) is a top view which shows the other modification of the spacer applied to the extrusion mold which concerns on embodiment of this invention, (b) is the sectional drawing.

  FIG. 1 shows an extrusion mold 9 in which a shaft-like core 1 is joined to a mandrel 3 and a die 7 is joined to a die body 5 into which the mandrel 3 is inserted. The drawings refer to FIGS. 1 to 3 unless otherwise specified. The temperature control structure 11 of the extrusion mold includes an insertion hole 13 that penetrates the core 1 and the mandrel 3 in the axial direction, an inner heater 15 attached to the core 1 and the mandrel 3 from the inside of the insertion hole 13, an inside mandrel 17, A refrigerant introduction pipe 19 that is inserted into the insertion hole 13 of the core 1 and introduces a refrigerant into the inside mandrel 17, and outer heaters 21 and 23 provided in the die body 5 and the die 7 are provided.

  The mandrel 3 has a flange 25 provided at one end thereof attached to the die body 5 with bolts or the like. The other end of the mandrel 3 is smoothly connected to the core 1. The illustrated mandrel 3 has the other end facing upward, but the orientation in which the extrusion mold 9 is used is not limited to this posture. An introduction path 27 and a plurality of spiral grooves 29 are formed on the peripheral surface of the mandrel 3. An adjuster string 33 is attached to the end of the die body 5 with a bolt or the like, and the die 7 is positioned inside the adjuster string 33 so as to form a circular gap 31 around the core 1.

  The inner heater 15 is a cylindrical electric heater called a brass cast heater disposed around the refrigerant introduction pipe 19 via a gap 35. The outer heaters 21 and 23 are electric heaters called band heaters wound around the peripheral surfaces of the die 7 and the die body 5. The inside mandrel 17 is a cylindrical hollow body in which a cold storage chamber 37 for introducing a refrigerant is formed. It is preferable to provide a small taper on the outer peripheral surface of the inside mandrel 17 so that the diameter of the inside mandrel 17 decreases as it moves away from the other end of the mandrel 3 in the direction indicated by the arrow F.

  The refrigerant introduction pipe 19 also serves as a support that supports the inside mandrel 17 at a position sandwiching the gap 39 with respect to the core 1. The material of the refrigerant introduction pipe 19 is copper or stainless steel. Moreover, you may connect both by screwing the external thread formed in any one of the inside mandrel 17 and the edge part of the refrigerant | coolant inlet tube 19 with the internal thread formed in the other of both. Or you may weld both.

  The thermoplastic resin used as the raw material of the seamless product is melted in advance outside the extrusion mold 9 and is supplied between the mandrel 3 and the die body 5 from the adapter nozzle 41 provided in the die body 5 through the introduction path 27. And flows into the spiral groove 29. Further, the thermoplastic resin flows in the direction indicated by the arrow F while filling the space between the mandrel 3 and the die body 5, and becomes a cylindrical seamless product when pushed out from the gap 31. Further, the inside mandrel 17 is fitted inside the seamless product immediately after being pushed out from the gap 31 to restrict the seamless product from contracting in the radial direction.

  According to the temperature control structure 11 of the extrusion mold described above, the heat of the inner heater 15 and the outer heaters 21 and 23 is conducted to the core 1 and the mandrel 3, but the heat to be conducted to the inside of the insertion hole 13 is a gap. It can be cut by 35. Further, the inside mandrel 17 is thermally insulated from the core 1 by a gap 39. Thereby, it is possible to suppress the heat of the inner heater 15 and the outer heaters 21 and 23 from escaping to the refrigerant, and to effectively heat the raw material with the heat of the inner heater 15 and the outer heaters 21 and 23.

  In addition, according to the temperature control structure 11 of the extrusion mold, the temperature of the inner mandrel 17 is not affected by the heat of the inner heater 15 and the outer heaters 21 and 23, so that it is set to ensure good fluidity of the thermosetting resin. Regardless of the heat generation temperatures of the inner heater 15 and the outer heaters 21 and 23, seamless products using any thermosetting resin as a raw material can be manufactured with stable quality. The alternate long and short dash lines indicated by reference numeral 38 indicate the positions of thermocouples for measuring temperatures at four locations of the extrusion mold 9. For example, when extrusion molding is performed using a fluororesin as a raw material, the heat generation temperatures of the inner heater 15 and the outer heaters 21 and 23 are controlled so that the temperatures at the four locations described above can be maintained at about 450 ° C. Thus, the inside mandrel 17 is not heated.

  Furthermore, the temperature control structure 11 of the extrusion mold preferably connects the refrigerant introduction pipe 19 to the core 1 and the mandrel 3 via spacers 43 and 45 that secure a gap 35 around the refrigerant introduction pipe 19. . The spacers 43 and 45 may be any member that positions the inside mandrel 17 supported by the refrigerant introduction pipe 19 on the core 1. In particular, as the spacer 43, an annular portion 44 that fits into the insertion hole 13 and allows the refrigerant introduction tube 19 to pass inside, and a tooth shape portion 46 that protrudes toward the inside of the annular portion 44 and sandwiches the refrigerant introduction tube 19 are integrated. It is preferable to apply a molded one. In this case, since the tooth profile 46 is a plurality of projections having a small area in contact with the refrigerant introduction pipe 19, the heat of the inner heater 15 and the outer heaters 21 and 23 is prevented from being conducted to the refrigerant introduction pipe 19 through the spacer 43. it can. The spacer 45 may be the same as the spacer 43.

  The refrigerant introduction pipe 19 is preferably a double pipe in which the feed pipe 47 is inserted inside the return pipe 49 for the following reason. That is, the feed water 47 serving as the coolant is supplied to the feed tube 47 of the coolant introduction tube 19 from a mold temperature control device not shown in the drawing. The refrigerant passes through the feed pipe 47 in the direction indicated by the arrow F, hits the end face 51 when it reaches the cold storage chamber 37 of the inside mandrel 17, and reverses its flowing direction. Subsequently, the refrigerant discharged from the cold storage chamber 37 to the return pipe 49 circulates through the return pipe 49 to the mold temperature controller. Although it is impossible to completely prevent the refrigerant introduction pipe 19 from receiving the radiant heat from the inner heater 15, the refrigerant passing through the feed pipe 47 reaches the cold storage chamber 37 by absorbing the radiant heat into the refrigerant discharged from the cold storage chamber 37. Unnecessary heating can be prevented.

  Further, according to the temperature control structure 11 of the extrusion mold, when molding is performed using a polyolefin-based resin as a raw material, the raw material may be heated only by the heat of the outer heaters 21 and 23 and the inner heater 15 may not be energized. The amount of heat generated by the outer heaters 21 and 23 is smaller than that of the inner heater 15, and most of the heat of the outer heaters 21 and 23 is released to the atmosphere before being transmitted to the die 7. For this reason, since the die 7 cannot be maintained at about 450 ° C. as described above only by the heat generated by the outer heaters 21 and 23, the temperature control structure 11 of the extrusion mold is indispensable for the inner heater 15 and the outer heaters 21 and 23. As an element.

  In addition, this invention can be implemented also in the aspect which added various improvement, correction, or a deformation | transformation based on the knowledge of those skilled in the art within the range which does not deviate from the meaning, and may be implemented in the following aspects. As shown in FIG. 4, a plurality of rod-shaped inner heaters 15 may be attached to the core 1, and the refrigerant introduction pipe 19 is shielded from the inner heater 15 by the heat insulating material 48, and the refrigerant is heated by the radiant heat from the core 1. It may be suppressed. As shown in FIG. 5, the inner heater 15 may be immersed in the core 1.

  As shown in FIG. 6A, the tooth profile 46 of the spacer 43 may be four protrusions that come into contact with the coolant introduction pipe 19. In order to further reduce the area of the tooth profile portion 46 in contact with the refrigerant introduction pipe 19, the inclined surface 50, 52 is formed on the tooth profile portion 46 as shown in FIG. May be Yamagata. A plurality of through holes 53 for restricting heat conduction may be formed in the annular portion 44.

  As shown in FIGS. 7A and 7B, the tooth profile 46 of the spacer 45 may be two arc-shaped protrusions that contact the refrigerant introduction pipe 19, and the inclined surfaces 50 and 52 are formed on the tooth profile 46. May be formed. In this case, notches 54 and 55 may be formed in the ring-shaped portion 44, and the thermocouple and the lead wire of the inner heater 15 may be passed inside the notches 54 and 55. Reference numeral 56 denotes a bolt insertion hole for fixing the spacer 43 to one end of the mandrel 3.

  The present invention is a useful technique for molding any annular product in addition to the manufacture of precision electronic components.

  DESCRIPTION OF SYMBOLS 1 ... Core, 3 ... Mandrel, 5 ... Die body, 7 ... Adjustable string, 9 ... Extrusion mold, 11 ... Temperature control structure of extrusion mold, 13 ... Insertion hole, 15 ... Inner heater, 17 ... Inside mandrel, DESCRIPTION OF SYMBOLS 19 ... Refrigerant introducing pipe, 21, 23 ... Outer heater, 25 ... Flange, 27 ... Introducing path, 29 ... Spiral groove, 31 ... Gap, 33 ... Adjustable, 35, 39 ... Air gap, 37 ... Cold storage chamber, 41 ... Adapter nozzle , 43, 45 ... spacer, 44 ... ring-shaped part, 46 ... tooth form part, 47 ... feed pipe, 48 ... heat insulating material, 49 ... return pipe, 50, 52 ... inclined surface, 51 ... end face, 53 ... through hole, 54, 55 ... Notch.

Claims (6)

A thermoplastic resin that is supplied between the mandrel and the die body by joining an axial core to the mandrel, joining a die that forms a gap around the core to the die body into which the mandrel is inserted. Is a temperature control structure of an extrusion mold that is molded into a cylindrical shape by extruding from the gap,
An insertion hole that penetrates the core in the axial direction, an inner heater provided in the core, an inside mandrel that regulates radial shrinkage of the thermoplastic resin extruded from the gap, and the insertion hole that is inserted through the insertion hole of the core A temperature of an extrusion mold, comprising: a refrigerant introduction pipe for introducing a refrigerant into the inside mandrel; and an outer heater provided in the die, wherein the inner heater is disposed around the refrigerant introduction pipe via a gap. Tonal structure.   The said inside mandrel is supported by the said refrigerant | coolant inlet tube in the position which pinches | interposes a space | gap with respect to the said core, and it inserts inside the cylindrical thermoplastic resin extruded from the said gap | interval. Temperature control structure of extrusion mold.   The temperature control structure of an extrusion mold according to claim 1 or 2, wherein the refrigerant introduction pipe is connected to the core via a spacer that secures a gap around the refrigerant introduction pipe.   The spacer includes an annular portion that fits into the insertion hole and allows the refrigerant introduction tube to pass inside, and a tooth shape portion that protrudes toward the inside of the annular portion and sandwiches the refrigerant introduction tube. The temperature control structure of an extrusion mold according to any one of claims 1 to 3.   The inside mandrel has a cold storage chamber for introducing a refrigerant, and the refrigerant introduction pipe has a feed pipe through which the refrigerant supplied to the cold storage chamber passes inside a return pipe through which the refrigerant discharged from the cold storage chamber passes. The temperature control structure for an extrusion mold according to any one of claims 1 to 4, wherein the temperature control structure is an inserted double pipe.   The temperature control structure of an extrusion mold according to any one of claims 1 to 5, wherein the refrigerant introduction pipe is shielded from the inner heater by a heat insulating material.

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