JP2009039995A - Injection molding die - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an injection molding die allowing work to be performed very efficiently in taking out a runner molding for a color change or the like of a molding as an insulated type injection molding die and reducing a maintenance cost without a risk of causing the damage and deformation of a torpedo tip part. <P>SOLUTION: A die body 1 of a fixed side die F is provided with a sprue S2 extending from a runner R to a gate G of a cavity C. The gate G is formed as an open gate which is normally open. The sprue S2 comprises a non-heating part S2a on the runner R side, and a heating part S2b by a heater 4 on the gate G side. When a mounting plate 2 and the die body 1 are separated after injection molding, solidified resin Ro in the non-heating part S2a of the sprue S2 is separated from melted resin Re in the heating part S2b and detached from the die body 1 integrally with the runner molding RM. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an injection mold having a split surface for taking out a runner molded product as an insulated method, and having a cavity inlet serving as an open gate.

Conventionally, in the injection molding of thin plastic containers such as cups and trays, a hot runner has been used as a means for shortening the molding cycle by eliminating the trouble of taking out the solidified resin in the mold flow path (runner and sprue) every molding cycle. A method (also referred to as a full hot method) and an insulated method (also referred to as a thermal insulation runner method) are frequently used (Cited document 1).
JP 7-148767 A (paragraphs 0002 to 0004)

  The former hot runner method enables continuous molding by keeping the resin in the entire mold flow channel in a molten state by a heating mechanism, and the runner is generally used as a flow channel hole inside a manifold with a heater. Is provided. There is also a valve gate type in which a valve pin for opening and closing the gate is arranged in a sprue from the runner to the gate of the cavity. However, in such a hot runner method, it is necessary to set the heating temperature to a relatively high temperature in order to maintain the resin in the entire mold flow path in a molten state, and in addition to the high energy cost, Resin burns tend to occur, requiring precise control of the heating temperature and complicating molding condition settings, and the previous resin in the mold flow path is clean when changing colors. There is also a problem in that the die manufacturing cost is high due to the need for advanced technology for designing and processing the die flow path.

  On the other hand, in the latter insulated method, instead of providing a heating mechanism in the runner part, the runner diameter is set large (generally about φ16 to 20 mm), and the resin solidified on the inner peripheral side is used as a heat insulating layer. In addition, continuous molding can be performed with a molten resin flowing through the center (generally about φ8 mm), and the cavity entrance is an open gate that is always open. In recent years, however, as such an insulated mold, the sprue from the runner to the gate is set to a large diameter, and a torpedo is arranged inside, and the inflow of resin at the gate depending on the position and shape of its tip In addition to fine adjustment of the state and the separation state at the time of taking out the product, heating with the internal heater of the topy to prevent clogging of the resin in the sprue has become widespread.

  FIG. 4 shows a configuration example of a conventional insulated injection mold, in which F is a fixed side mold, M is a movable side mold, and the mold body 7 of the fixed side mold F and A runner R is formed between the mounting plate 8. The mold body 7 of the fixed side mold F includes a mold plate 71, a runner plate 72 that is superposed on the back surface thereof and screwed and fixed thereto, and a disk shape that is screwed and fixed to the front side of the runner plate 72. And an annular cavity block 74 that is fixed to the template 71 with screws and fitted into the gate insert 73. The mold body 9 of the movable side mold M includes a mold plate 91, a receiving plate 92 which is superposed on the back surface thereof and fixed by screwing, and a cylindrical shape screwed and fixed to the front side of the mold plate 91. The core 93, the stripper plate 94 disposed on the front side of the template 91, the stripper ring 95 that is screwed and fixed to the stripper plate 94 and is fitted outside the core 93, and the substantially round shaft-like shape that is fitted inside the core 93. It consists of a core insert 96.

  The mounting plate 8 of the fixed-side mold F has a locating ring 81 fixed to the back side, and forms a primary sprue S1 that penetrates in the thickness direction at the center position of the locating ring 81 and continues to the runner R. A torpedo T that has an internal heater H with a pin-like shape pointed from the back side is inserted into the toped attachment hole 8a that penetrates in the thickness direction at the outer side of 81 in a state that the tip Ta side half protrudes to the front side. The pressing plate 82 that is in contact with the top end portion of the topped T is screwed. On the other hand, the mold body 7 on the fixed side is provided with a secondary sprue S2 that extends from the runner R through the runner plate 72 and the gate insert 73 to the gate G of the cavity C, and a topped T that protrudes from the mounting plate 8. Is inserted into the secondary sprue S2 and the tip Ta faces the gate G.

  In such an injection mold, since the resin of the primary sprue S1 and the runner R cannot be returned to the molten state once solidified, the runner molded product is removed when the molding is stopped for color change of the molded product. However, at this time, the resin of the secondary sprue S2 is also solidified by stopping the internal heater H and taken out integrally with the runner molding. That is, as shown in FIG. 4A, when the mold body 7 on the fixed side and the mounting plate 8 are separated, the solidified resin SR2 of the secondary sprue S2 is removed from the mold body 7 in a state of wrapping the topped T. Detached and held on the side of the mounting plate 8 integrally with the runner molding RM, then the inner surface side is melted by the temperature rise of the topped T to be detached from the toped T, and as shown in FIG. 4 (B) The runner molding RM is removed from the plate 8 together. In addition, the solidified resin SR1 of the primary runner S1 provided on the mounting plate 8 is also integrated with the runner molding RM.

  However, in the insulated injection mold as described above, when taking out the runner molding RM, it takes time to stop the internal heater H of the topped T and cool and solidify the entire resin of the secondary sprue S2. In addition, in order to remove the solidified resin SR2 after detachment from the mold body 5 from the topped T, it is necessary to raise the temperature of the toped T, and there is a problem that work efficiency is poor. Moreover, since the accuracy and production efficiency of the molded product are affected by the shape of the tip Ta and the distance from the gate G, the topped T cannot be used even if the tip Ta portion is deformed or worn on the order of 0.1 mm. However, when the above runner molded product RM is taken out, it is exposed in a state of protruding from the mounting plate 8, so that it is often inadvertently damaged and deformed at the end of the work, and must be replaced. It was. Furthermore, in the normal molding cycle of this type of conventional injection mold, if the gate G part is structurally cooled too much, resin clogging occurs, so that sufficient cooling action cannot be applied to the gate G part and molding is performed accordingly. There was also a drawback that the cooling and curing of the product was delayed and the molding efficiency was lowered.

  In view of the above situation, the present invention can perform the operation extremely efficiently when taking out a runner molded product for the purpose of color change of the molded product as an injection mold of the insulated method, It is intended to provide a product that can reduce the maintenance cost and can improve the molding efficiency in the normal molding cycle without causing any concern about the accuracy and production efficiency of the molded product due to the damage or deformation of the torpedo tip. .

  If the means for achieving the above object is shown with reference numerals in the drawings, the invention of claim 1 is that the runner molding RM is taken out between the mounting plate 2 of the fixed mold F and the mold body 1. In an insulated injection mold having a split surface P2 for use, a sprue (secondary sprue S2) extending from the runner R formed between the split surfaces P2 to the gate G of the cavity C is formed in the mold body 1. ), And the gate G forms an open gate that is always open, and the sprue S2 has a heating part S2b surrounded by a non-heating part S2a on the runner R side and a heater (coil heater 4) on the gate G side. When the mounting plate 2 and the mold body 1 are separated after injection molding, the solidified resin Ro in the non-heated part S2a of the sprue S2 is separated from the molten resin Re in the heated part S2b and run. Made is configured to disengaged from the mold body 1 over molding RM integrally.

  According to a second aspect of the present invention, in the injection mold according to the first aspect, the non-heating portion S2a of the sprue S2 is configured to have a large diameter and has a shape that decreases in diameter toward the small-diameter heating portion S2b. It is supposed to be.

  According to a third aspect of the present invention, in the injection mold according to the first or second aspect, at least the heating part S2b of the sprue S2 is inserted into and fixed to the mold body 1 of the fixed mold F. The center hole 30 is configured.

  According to a fourth aspect of the present invention, in the injection mold according to the third aspect, a resin reservoir 17 that converges toward the gate G is formed before the gate G, and the distal end portion of the cylindrical shaft member 3 has a sharp tip 31a. A plurality of conical topped portions 31 facing the gate G are arranged in the resin reservoir 17, and a peripheral surface of the toped 31 is branched from the central hole 30 of the cylindrical shaft member 3 to communicate with the resin reservoir 17. The channel holes 32, 32 are opened.

  Next, the effect of the invention based on the above configuration is shown with reference numerals in the drawings. First, according to the invention of claim 1, in the injection mold of the open gate by the insulated method, the fixed side mold Since the sprue S2 from the runner R of F to the gate G is composed of a non-heating part S2a on the runner R side and a heating part S2b on the gate G side, the mounting plate 2 and the mold body after injection molding due to color change of the molded product 1 is separated from the molten resin Re in the heating part S2b and detached from the mold body 1 integrally with the runner molding RM, and the mounting plate Held on two sides. Therefore, in the operation of taking out the runner molded product RM, it is not necessary to wait until the entire resin in the sprue S2 is cooled and solidified as in the prior art, and the solidified resin Ro held on the mounting plate 2 side is a single lump. Thus, since the member such as the topede is not surrounded, it can be easily detached from the mounting plate 2 integrally with the runner molded product RM without heating, and a high working efficiency can be obtained. Further, the heating part S2b of the sprue S2 can be formed thinly inside the heater 4, and the amount of molten resin that contacts the constituent members of the gate G is smaller than in the case where the outside of the conventional topped with an internal heater is used as a flow path. Thus, since the cooling on the gate G side can be accelerated in the normal molding cycle, the cooling efficiency of the molded product can be increased to increase the molding efficiency.

  According to the second aspect of the present invention, the non-heating portion S2a of the sprue S2 has a large diameter and a shape that decreases toward the small heating portion S2b. As with the diameter runner R, the solidified resin on the inner circumference side is used as a heat insulating layer to ensure the circulation of the molten resin at the center, so that resin clogging at the sprue S2 can be reliably prevented, and the runner molding RM can be removed. Even when the central portion of the internal resin is uncured, it can be separated from the molten resin Re of the heating portion S2b without any trouble, and the working time can be reduced accordingly.

  According to the invention of claim 3, since at least the heating part S2b of the sprue S2 is constituted by the central hole of the cylindrical shaft member 3, when the heating part S2b is provided in the mold body 1 of the fixed-side mold F, The cylindrical shaft member 3 is inserted into and fixed to the mold main body 1 and a heater 4 may be disposed around the cylindrical shaft member 3, thereby facilitating the assembly work of the fixed-side mold F.

  According to the invention of claim 4, in the resin reservoir 17 provided in front of the gate G, the gate side tip of the cylindrical shaft member 3 is arranged as a topped 31 with the tip 31a facing the gate G, Since the molten resin supplied to the sprue S2 flows into the cavity C from the gate G through the flow passage holes 32, 32 branched from the center hole 30 of the cylindrical shaft member 3 and through the resin reservoir 17, Similarly, the inflow state of the resin at the gate G and the separation state at the time of taking out the product can be adjusted by the topid 31, but there is no concern of causing deformation or damage because the tope 31 is not exposed to the outside in the work of taking out the runner molded product RM. .

  Hereinafter, an embodiment of an injection mold according to the present invention will be specifically described with reference to the drawings. FIG. 1 is a longitudinal sectional view of a main part of an injection mold, FIG. 2 is an enlarged longitudinal sectional view of a secondary sprue portion of the mold, and FIG. 3 is a longitudinal sectional view showing a runner molding taken out from the mold. It is.

 This injection mold is of an insulated open gate type, and is used for a cup-shaped thin molded product between a fixed mold F and a movable mold M as shown in FIG. A runner R is formed between the mold body 1 of the fixed mold F and the mounting plate 2, and a molded product is taken out between the fixed mold F and the movable mold M. In addition to the split surface P1 for use, a split surface P2 for taking out the runner between the mold body 1 and the mounting plate 2 of the fixed mold F is provided.

  The mold body 1 of the fixed mold F is sequentially fixed to the back side of the mold plate 10 by the first back plate 11, the second back plate 12, and the runner plate 13. In addition, a short cylindrical cavity block 14 and a substantially disk-shaped gate nest 15 fitted on the back side thereof are fitted in the hole 10a that penetrates in the thickness direction of the template 10, and further, A cylindrical shaft member 3 having a large-diameter head 3a penetrates through the first and second back plates 11 and 12 so as to protrude into the axial center position of the gate insert 15, and the cylindrical shaft member 3 A coil heater 4 is fitted around the shaft portion 3b. Thus, the cavity block 14 is screwed to the template 10, and the gate insert 15 is sandwiched between the cavity block 14 and the first back plate 11.

  A heater wiring groove 12a is formed on the front side of the second back plate 11, and the wiring board 16 is screwed. Further, although not shown, a temperature sensor for detecting the temperature of the cylindrical member 3 is mounted at a position near the end of the coil heater 4 on the gate G side, and the coil is detected based on the detection signal of the temperature sensor. By controlling the heater 4 on and off, the cylindrical member 3 is maintained at a constant temperature at which the resin in the center hole 30 is in an appropriate molten state. The temperature sensor is wired through a wiring groove (not shown) along the axial direction provided on the outer peripheral surface of the cylindrical member 3.

  The mounting plate 2 of the fixed mold F has a locating ring 21 fixed to the back side, and forms a primary sprue S1 that penetrates in the thickness direction at the center of the locating ring 21 and communicates with the runner R. Further, a secondary sprue S2 extending from the runner R to the gate G of the cavity C through the through hole 13a provided in the runner plate 13 of the mold body 1 and the center hole 30 of the cylindrical shaft member 3 concentrically communicating therewith. Is configured. The secondary sprue S2 has a region extending from the through hole 13a of the runner plate 13 to the head 3a of the cylindrical shaft member 3 in the region of the shaft portion 3a surrounded by the non-heating portion S2a and the coil heater 4 of the cylindrical shaft member 3. Becomes the heating part S2b, and the non-heating part S2a is configured to have a large diameter and is reduced in diameter toward the small heating part S2b.

  As shown in an enlarged view in FIG. 2, the gate insert 15 is formed with a substantially conical resin reservoir 17 converging toward the gate G before the gate G, and the cylindrical shaft member 3 is formed in the resin reservoir 17. The gate side tip is arranged as a topped 31. The topid 31 has a substantially conical shape with a bottom diameter smaller than that of the resin reservoir 17, and the tip 31 a faces the gate G, and a plurality of flow branches from the central hole 30 of the cylindrical shaft member 3 on the conical circumferential surface. The passage holes 32, 32 are open.

  The gate insert 15 has a plurality of cooling water passages 18a at the interface with the first back plate 11 and cooling water passages 18b at the interface with the portion extending from the mold plate 10 to the cavity block 14, respectively. A plurality of cooling water holes 18c are formed so as to enter the center side obliquely from the interface with the first back plate 11 and return to the interface in a V shape. Furthermore, a plurality of cooling water passages 19 are formed in the cavity block 14 at the interface with the template 10.

  On the other hand, as shown in FIG. 1, the mold body 5 of the movable side mold M includes a mold plate 50, a receiving plate 51 superposed on the back surface thereof, and a substantially cone screwed and fixed to the front surface side of the mold plate 50. It comprises a base-like core 52, a stripper plate 53 disposed on the front side of the template 50, and a stripper ring 54 that is screwed and fixed to the stripper plate 53 and fitted onto the core 52. The core 52 has a core insert 52b fitted inside the cylindrical main body 52a, and a cooling water inlet / outlet passage 6a and an air introduction passage 6b extending to the outside of the mold are provided in the core insert 52b. Further, a plurality of annular grooves 55... Constituting a cooling water flow path communicating with each other are densely formed on the outer peripheral portion of the core insert 52b that forms an interface with the cylindrical main body 52a.

  1 and 2, only one cavity C is shown as a representative, but it goes without saying that the entire injection mold has a plurality of cavities C having the same structure. Thus, details of the cooling water circuit connected to the cooling water passages 18a, 18b, the cooling water holes 18c, the cooling water passage 19, etc. in the fixed mold F, the cooling water inlet / outlet path 6a in the movable mold M, and the like. The details of the cooling water circuit connected to the annular grooves 55 are not shown. Also, the operation mechanism and operation guide portion of the mounting plate 2 of the fixed mold F, the operation mechanism and operation guide portion of the mold body 5 and the stripper plate 53 of the movable mold M, and the mounting plate of the movable mold M. Also, illustration is omitted.

  In the injection molding using the injection mold having the above-described configuration, molten resin supplied from a heating cylinder (not shown) is filled from the primary sprue S1 through the runner R and the secondary sprue S4 into the cavity C. At the end of the sprue S4, the resin pool 17 enters through the flow passage holes 32, 32 branched from the center hole 30 of the cylindrical shaft member 3, and flows into the cavity C from the gate G through the resin pool 17. Then, after the resin filled in the cavity C is cooled and cured, the mold body 5 of the movable mold M is separated from the fixed mold F by the dividing surface P1, and the molded product covering the core 52 is taken from the inside. The air is released by the stripper plate 53 with the release of air. During this time, the heating part S2b of the secondary sprue S2 maintains a predetermined melting temperature by heating with the coil heater 4, but the primary sprue S1 and the runner R and the non-heating part S2a of the secondary sprue S2 have a large diameter. Since the resin solidified at the inner peripheral portion is used as a heat insulating layer, the central portion is maintained in a molten state, and the flowability of the molten resin is ensured. Therefore, the molding operation can be continuously performed without causing resin clogging.

  Thus, in this molding cycle, since the resin in the heating part S2b including the resin reservoir 17 of the secondary sprue S2 can be maintained in the molten state by the coil heater 4 as described above, after the molten resin is injected and filled into the cavity C In particular, the cooling degree of the gate insert 15 is enhanced by heat exchange with the cooling water passing through the cooling water passages 18a, 18b, and the cooling water holes 18c ... Thus, the molding efficiency is improved.

  On the other hand, when the molding is stopped by changing the color of the molded product, the runner plate 2 is separated from the mold body 1 of the fixed mold F, and the runner molded product RM is taken out. At this time, in the secondary sprue S2, the solidified resin Ro in the non-heated part S2a is separated from the molten resin Re in the heated part S2b, and the solidified resin Ro is detached from the mold body 1 integrally with the runner molding RM, As shown by the phantom line in FIG. 5, the holding plate 2 is held, and then, as shown by the solid line in FIG. 5, it is detached from the mounting plate 2 as an integral runner molding RM together with the solidified resin SR1 of the primary sprue S1. When the runner plate 2 is separated from the mold body 1, the resin in the non-heated part S2a in the secondary sprue S2 is heated in the heated part S2b because the outer peripheral part is solidified even when the central part is uncured. Can be separated from the molten resin Re without any trouble.

  In such an operation of taking out the runner molding RM, when the mounting plate 2 is separated from the mold body 1, it is not necessary to wait until the entire resin in the sprue S2 is cooled and solidified as in the prior art. In addition to being able to perform the separation operation, the solidified resin Ro held on the side of the mounting plate 2 after the separation is a single lump and does not surround a member such as a torpedo. Therefore, it can be easily detached from the mounting plate 2 integrally with the runner molding RM, so that a very high working efficiency can be obtained.

  In addition, the heating part S2b of the secondary sprue S2 is configured by the center hole 30 of the cylindrical shaft member 3, and the gate side tip of the cylindrical shaft member 3 is disposed in the resin reservoir 17 in front of the gate G as a topped 31. Therefore, when assembling the fixed mold F, the cylindrical shaft member 3 is inserted into and fixed to the mold main body 1 and the heater 4 is arranged around it. 31 can adjust the inflow state of the resin in the gate G and the separation state when the product is taken out. Moreover, since the toped 31 is not exposed to the outside in the work of taking out the runner molded product RM, there is no fear of causing deformation or damage of the tip as in the prior art, and the maintenance cost of the injection mold is reduced by extending its life. .

  In addition, in the said embodiment, although the cylindrical shaft member 3 bears a part of non-heating part S2a of the secondary sprue S2 and the heating part S2b, the whole secondary sprue S2 is comprised with the cylindrical shaft member 3. Is also possible. In addition, in the injection mold according to the present invention, the shape of the cavity C, the shape and configuration of the mold parts that form the cavity C, the shape of the cylindrical shaft member 3, and the flow path hole 32 that opens in the peripheral surface of the topped 31. In addition to the embodiment, various design changes can be made to the detailed configuration, such as the number of components, the member configuration of the fixed-side mold F and the movable-side mold M, the arrangement configuration of the cooling water channel 60, and the like.

The vertical side view of the principal part of the injection mold which concerns on one Embodiment of this invention. The vertical side view which expands and shows the secondary sprue part of the injection molding die. The vertical side view which shows the extraction state of the runner molding in the same injection mold. The longitudinal side view which shows the structural example of the injection mold of the conventional insulated method. The operation of taking out the runner molding in the conventional injection mold is shown, (A) is a longitudinal side view of the state where the mounting plate is separated from the mold body of the stationary mold, and (B) is from the mounting plate. It is a vertical side view of the state where the runner molding was made to detach.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Mold body 17 Resin pool 2 Mounting plate 3 Cylindrical shaft member 30 Center hole 31 Toped 31a Pointed end 32 Flow path hole 4 Coil heater (heater)
5 Mold body C Cavity F Fixed mold G Gate M Movable mold P1 Dividing surface P2 Dividing surface R Runner Ro Solidified resin Re Molten resin RM Runner molded product S2 Secondary sprue (sprue)
S2a Non-heating part S2b Heating part

Claims (4)

In an insulated injection mold where the fixed plate mold mounting plate and the mold body form a split surface for taking out the runner molding,
The mold body is provided with a sprue from the runner formed between the divided surfaces to the gate of the cavity, and the gate forms an open gate that is always open,
The sprue consists of a non-heating part on the runner side and a heating part surrounded by a heater on the gate side,
When the mounting plate and the mold body are separated after injection molding, the solidified resin in the non-heated part of the sprue is separated from the molten resin in the heated part so as to be detached from the mold body integrally with the runner molding. An injection mold made up of.   2. The injection mold according to claim 1, wherein the non-heating portion of the sprue is configured to have a large diameter, and has a shape that is reduced in diameter toward the small heating portion.   The injection mold according to claim 1 or 2, wherein at least the heating portion of the sprue is configured by a center hole of a cylindrical shaft member that is fitted and fixed to a mold body of a fixed side mold.   A resin reservoir that converges on the gate side is formed in front of the gate, and the tip end on the gate side of the cylindrical shaft member is disposed in the resin reservoir as a substantially conical toroid with the tip facing the gate. The injection mold according to claim 3, wherein a plurality of flow path holes branched from the center hole of the cylindrical shaft member and communicating with the resin reservoir are opened on the peripheral surface of the mold.

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