JP2007203561A - Nozzle for injection molding machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nozzle for an injection molding machine which is applicable to a small injection molding machine used as a handy type or on a table, secures the heat insulation of the nozzle without causing the enlargement of the nozzle and the complication of its structure, and can keep a stable temperature of a molten resin, and thus can be operated in a high cycle. <P>SOLUTION: The nozzle is a nozzle 6 used for the injection molding machine 1 which comprises a plasticization barrel 2 which plasticizes and injects a resin material, a hopper 3 which stores a pellet of a resin material to be supplied to the polasticization barrel 2, a plunger 4 which presses the resin material plasticized in the plasticization barrel 2, and a drive mechanism 5 of this plunger 4. The whole nozzle 6 is formed of a material having heat insulation property. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a nozzle for an injection molding machine used to obtain a resin molded product by injecting and filling a resin material into a mold cavity, and more specifically, a handy type injection molding machine handled manually by an operator, The present invention relates to a nozzle for an injection molding machine suitably used as a nozzle for a small injection molding machine or the like used on a table.

  Conventionally, nozzles used in injection molding machines have been entirely made of a metal material having good thermal conductivity. In the injection molding of a thermoplastic resin, a mold for solidifying a molten resin usually has a temperature lower than the solidification temperature of the molten resin (for example, 100 ℃ ~ normal temperature). On the other hand, the nozzle is attached to the tip of the heating barrel so as to be integrated with the heating barrel, and forms a molten resin flow path between the heating barrel and the mold, and is usually at a high temperature (for example, 180 ° C.) higher than the solidification temperature of the molten resin. About 300 ° C.).

  When performing injection molding, the tip of the nozzle of the injection molding machine comes into contact with the mold, and heated molten resin is injected from the tip of the nozzle into the mold, and then cooled and solidified to obtain a molded product. When the tip of the nozzle comes into contact with the mold, the heat of the nozzle is transferred to the mold having a low temperature due to heat conduction, and the temperature of the nozzle decreases. For this reason, in the heating barrel of the injection molding machine, the plasticizing and metering step of melting the molding resin is performed in a state where the nozzle and the mold are separated in order to prevent solidification of the molten resin due to the temperature drop of the nozzle. Thus, immediately before the injection of the resin, the mold and the nozzle are brought into contact with each other to inject and fill the molten resin into the mold.

  However, in high cycle molding that shortens the injection molding cycle time, it is mainstream to perform continuous molding in a state where the mold and the nozzle are always in contact, and it is inevitable that heat is radiated from the nozzle to the mold. . Therefore, in order not to impair the fluidity of the molten resin inside the nozzle, the nozzle is thermally insulated.

  Known methods for heat insulating the nozzle include a method of covering the entire outside of the nozzle with a heat insulating layer (for example, see Patent Document 1), a method of providing a heat insulating ring between the nozzle and the injection device (for example, see Patent Document 2), and the like.

Japanese Patent No. 2675953 (0004, FIG. 7) Japanese Patent No. 3277321 (0010, FIG. 1)

  However, as described in Patent Document 1, when the entire nozzle is covered with a heat insulating material, there is a problem that the structure in the vicinity of the nozzle becomes complicated and the cost increases. In addition, as described in Patent Document 2, the provision of a heat insulating ring has a problem that the resin enters a minute gap between the heat insulating ring and the nozzle, and the risk of causing resin burning increases. Furthermore, heat insulation is insufficient with only the heat insulation ring.

  Moreover, the nozzle heat insulation means described in Patent Document 1 and Patent Document 2 have a large nozzle or a complicated structure. When trying to apply the conventional heat insulation means of the nozzle to a small injection molding machine, the small injection molding device has a small nozzle, so that processing is performed around the nozzle or complicated processing is performed on the nozzle itself. This is extremely difficult and cannot be applied in practice.

  In view of the above situation, the problem to be solved by the present invention can be applied to a handy type or a small-sized injection molding machine used on a desktop, and the nozzle is surely prevented without increasing the size of the nozzle or complicating the structure. An object of the present invention is to provide a nozzle for an injection molding machine capable of stabilizing the temperature of the molten resin by heat insulation and enabling a high cycle molding process.

  In order to solve the above-mentioned problems, the nozzle for an injection molding machine of the present invention is formed of a material having a heat insulating property as a whole.

  In the nozzle for an injection molding machine of the present invention, porous metal, ceramics, or plastic having a high heat deformation temperature can be used as the material having heat insulation properties.

  The nozzle for an injection molding machine of the present invention is composed of a nozzle body and a jacket covering the periphery of the nozzle body, or is composed of a nozzle body made of foamed stainless steel and a ceramic jacket covering the periphery of the nozzle body. The inner surface of the nozzle can be coated.

  The nozzle for an injection molding machine of the present invention is preferably used for a small injection molding machine having a clamping force of 5 tons or less.

  According to the nozzle for an injection molding machine according to the present invention, since the entire nozzle is formed of a heat insulating material, the nozzle can be insulated without being covered with a heat insulating material. It is possible to suppress the heat exchange of the mold and stabilize the mold temperature and the temperature of the injection device.

  Furthermore, the nozzle for an injection molding machine of the present invention does not cause an increase in the size of the nozzle or a complicated structure, unlike conventional nozzle heat insulation means, so it can be used as a handy type or a small injection molding machine used on a desktop. Applicable. In this case, even if the nozzle and the mold are always in contact, the nozzle is reliably insulated and the temperature of the molten resin can be stabilized, so the injection cycle time is shortened and high cycle molding is performed. Is possible.

Embodiments of the present invention will be described below in detail with reference to the drawings. The nozzle of the present invention is an injection molding machine nozzle used in an injection molding machine. FIG. 1 is a view showing the structure of the main part of an injection molding machine in which the nozzle for an injection molding machine of the present invention is used. In addition, in FIG. 1, the drive mechanism of the plunger showed the external appearance, and the other part showed the cross-sectional structure. The injection molding machine shown in FIG. 1 is a small-sized machine installed on a table, and has an ability to inject a resin material of 20 cm ³ or less, preferably 10 cm ³ or less per injection operation.

  An injection molding machine 1 shown in FIG. 1 includes a plasticizing barrel 2 that plasticizes and injects a resin material, a hopper 3 that stores pellets of the resin material to be supplied to the plasticizing barrel 2, and plasticizing in the plasticizing barrel 2. A plunger 4 for pressing the resin material formed, a drive mechanism 5 for the plunger 4, and a nozzle 6 for injection molding machine of the present invention for injecting the resin material pressed by the plunger 4 (hereinafter simply referred to as a nozzle). Prepare. A wire heater 7 wound in a coil shape over a predetermined length is attached to the outer peripheral surface of the plasticizing barrel 2 in order to heat the resin material supplied to the plasticizing barrel 2.

  FIG. 2 is a cross-sectional view showing an enlarged state near the nozzle tip of the injection molding machine. As shown in FIG. 2, the nozzle 6 is fixed to the tip of the plasticizing barrel 2. The plasticizing barrel 2 is provided with a nozzle fixing portion 11 that protrudes from the tip and is formed into a male screw shape. On the other hand, on the plasticizing barrel 2 side of the nozzle 6, there is provided a mounting portion 64 formed in a female screw shape so as to be screwed into the nozzle fixing portion 11. The nozzle 6 is fixed to the plasticizing barrel 2 by screwing the mounting portion 64 of the nozzle 6 into the nozzle fixing portion 11 at the tip of the plasticizing barrel 2.

  As shown in FIG. 1, the plasticizing barrel 2 of the injection molding machine 1 is formed in a cylindrical shape from a metal material or the like, and has a through-hole 12 penetrating in the longitudinal direction inside. The through-hole 12 has a large inner diameter on the plunger 4 side and a smaller inner diameter on the nozzle 6 side. The plasticizing barrel 2 is provided with a resin material supply unit 8 that opens to the outside, and a resin material supply pipe 9 that communicates with the hopper 3 is connected to the resin material supply unit 8. The plunger 4 is driven by the supply of hydraulic pressure from a hydraulic pressure source 10 disposed outside the drive mechanism 5, and pushes the plasticized resin material from the nozzle 6. In the injection molding machine of FIG. 1, the plunger type is used as the plasticizing method of the resin, but a screw type may be used as the plasticizing method.

  As shown in FIG. 2, the nozzle 6 shown in FIG. 1 is formed of a cylindrical body having a through-hole 60 inside and having a tapered tip at the tip side, and the whole is formed of a heat insulating material. Examples of the heat-insulating material used for the nozzle 6 include porous metals such as foamed stainless steel and foamed aluminum, ceramics such as alumina, alumina-silica, zirconia, silicon nitride, and silicon carbide, and plastics having a high thermal deformation temperature. Etc. are used. Any heat distortion temperature of the plastic can be used as long as it is higher than the plasticization temperature of the resin material to be used.

  As a heat insulating material used for the nozzle 6, foamed stainless steel is most preferable in terms of strength. Ceramics are excellent in heat insulation. In addition, plastic is inexpensive in cost, and is optimal for applications such as frequent replacement of the nozzle 6, and the nozzle 6 can be made disposable. The material of the nozzle 6 can be appropriately selected according to the type of the molded product.

  Since the material having the above-described heat insulation used for the nozzle 6 has lower fracture brittleness than general mold steel, it can prevent damage to the mold even when the nozzle touch force becomes excessive. There are advantages.

  The operation of the injection molding machine in FIG. 1 is as follows. When the plasticizing barrel 2 is heated by the heater 7 and the resin material pellets stored in the hopper 3 are supplied into the plasticizing barrel 2 through the resin material supply pipe 9 and the resin material supply unit 8, the resin material is plasticized. It is heated in the plasticizing barrel 2 and plasticized. The plunger 5 is actuated to press the plasticized resin material and eject from the tip of the nozzle 6. As shown in FIG. 2, the injected resin material passes through the sprue 22 of the mold 21 and is introduced into the mold cavity (not shown).

  The inner wall surface temperature of the plasticizing barrel 2 is adjusted to a temperature about 70 ° C. higher than the plasticizing temperature of the resin material. For example, when PBT (polybutylene terephthalate) is used as the resin material, the temperature is around 290 ° C., and when TPS (styrene thermoplastic elastomer material) is used, the temperature is around 280 ° C.

  When the front end of the nozzle 6 is brought into contact with the mold 21, the entire nozzle 6 is formed of a heat-insulating material. Therefore, heat conduction to the mold 21 side is prevented. As a result, when performing continuous molding with the nozzle always in contact, heat exchange between the plasticizing barrel 2 and the mold 21 of the injection molding machine 1 via the nozzle 6 is suppressed, and the temperature of the mold 21 and the plasticizing barrel are suppressed. The temperature of 2 can be stabilized.

  3A and 3B show another embodiment of the nozzle of the present invention, in which FIG. 3A is a cross-sectional view in the resin injection direction, and FIG. 3B is a cross-sectional view taken along line AA in FIG. The nozzle 6 may be formed uniformly with the same material as shown in FIGS. 1 and 2, but as shown in FIGS. 3A and 3B, the nozzle body in which the through hole 60 is formed. 61 and a jacket 62 covering the periphery of the nozzle body 61 can be configured. Moreover, it is good also as a layer structure of three or more layers. The nozzle body 61 and the jacket 62 may be made of the same material, but may be made of different materials.

  The nozzle body 61 and the jacket 62 preferably have different heat insulation properties. For example, the nozzle body 61 is made of foamed stainless steel having high strength but lower heat insulation than ceramics, and the jacket 62 is made of ceramics having better heat insulation than foamed stainless steel. Thus, it is possible to achieve both strength and heat insulating properties by forming a structure in which materials having different heat insulating properties are laminated in the thickness direction.

  As shown in FIGS. 3A and 3B, the nozzle 6 is integrally formed of the same material in the flow direction of the molded resin, and the through hole 60 serving as the resin flow path is like a conventional heat insulating ring. There are no joints of different materials. Therefore, there is no possibility that the molding resin leaks from a minute gap between the joint surfaces of the materials and causes problems such as resin damage.

  Further, as shown in FIGS. 3A and 3B, the nozzle 6 can be provided with a surface treatment layer 63 by coating the inner surface. As the coating material, ceramics, heat-resistant resin, or the like can be used. By coating the inside of the nozzle, the fluidity of the resin and the appearance of the molded product can be improved.

  In the nozzle 6, when the nozzle body 61 is formed of a porous material such as foamed aluminum or foamed stainless steel, the unevenness present on the surface of the through hole 60 affects the resin passing through the through hole 60. As a result, there is a possibility that the surface of the molded product becomes a satin finish or lacks gloss, resulting in a design failure. By coating the inside of the nozzle and providing the surface treatment layer 63 on the surface to form the surface smoothly, it is possible to prevent the surface of the molded product from becoming matte.

  The injection molding machine to which the nozzle 6 of the present invention is applied is preferably used for a small injection molding machine with a clamping force of 5 tons or less, more preferably a small injection molding machine with a clamping force of 1 tons or less. It is to be used for. With such an injection molding machine having a small mold clamping force, even a low-strength material can be used as the material of the nozzle, so that there is an advantage that the range of selection of the nozzle material is widened.

It is a figure which shows the structure of the principal part of the injection molding machine in which the nozzle for injection molding machines of this invention is used. It is sectional drawing which shows the state which expanded the nozzle tip vicinity of the injection molding machine. The other aspect of the nozzle of this invention is shown, (a) is sectional drawing of the injection direction of resin, (b) is the sectional view on the AA line of (a).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Injection molding machine 2 Plasticization barrel 3 Hopper 4 Plunger 5 Plunger drive mechanism 6 Nozzle 60 Through-hole 61 Nozzle body 62 Jacket 63 Surface treatment layer 64 Attachment part

Claims (8)

  A nozzle for an injection molding machine, characterized in that the entire nozzle is formed of a heat-insulating material.   The nozzle for an injection molding machine according to claim 1, wherein the material having heat insulation is a porous metal.   The nozzle for an injection molding machine according to claim 1, wherein the material having heat insulation is ceramics.   2. The nozzle for an injection molding machine according to claim 1, wherein the material having a heat insulating property is a plastic having a high heat distortion temperature.   2. The nozzle for an injection molding machine according to claim 1, comprising a nozzle body and a jacket covering the periphery of the nozzle body.   The nozzle for an injection molding machine according to claim 1, comprising a nozzle body made of stainless steel foam and a ceramic jacket covering the periphery of the nozzle body.   The nozzle for an injection molding machine according to any one of claims 1 to 6, wherein an inner surface of the nozzle is coated. The nozzle for an injection molding machine according to any one of claims 1 to 7, wherein the nozzle is used for a small injection molding machine having a clamping force of 5 tons or less.

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