JP2009241377A - Sprue bush and sprue bush device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sprue bush using a ceramic heater which hardly breaks as a heating means capable of keeping synthetic resin in molten state even with a simple structure. <P>SOLUTION: The sprue bush 1 is constituted by integrally forming a tabular base body 2 to be fixed to a metal mold, a cylindrical body 3 erected perpendicular to the base body 2 and in which a flow path of molten resin is formed in an axial center, and a tabular body 4 arranged parallel to the cylindrical body 3 and erected perpendicular to the base body 2. Further, the ceramic heater 10 is accommodated between the outer planar face 3c of the cylindrical body 3 and the inner planar face 4a of the plate like body 4. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a sprue bush heated by a heater, and more particularly to a simple sprue bush and a sprue bushing device that can be easily mounted on a mold.

  2. Description of the Related Art Conventionally, injection molding dies having a structure in which a heater is disposed in the vicinity of a sprue bush, a runner, and a gate so as to keep the injected molten resin in a molten state without solidifying. As the heater used for the mold having such a structure, various heaters such as a cartridge heater, a band heater, a heater wound in a coil shape, and the like are used. These heaters have good heating efficiency such as a short temperature rise time, and are not easily disconnected (failed) even if the heater is overheated due to floating from the installation part. It has been demanded. Further, not only heating is always performed, but heating is performed intermittently, and the resin state is often controlled between a molten state and a softened state, and in such a case, the heater is easily disconnected. A so-called ceramic heater may be used as a heater that is difficult to break under such conditions.

  In the molding die proposed in Patent Document 1, a band heater is used for heating the sprue bush, a cartridge heater is used for the manifold provided with the runner, and a band is provided on the outer periphery of the valve casing. A heater is used. The heater used here is presumed to be a conventional heater incorporating a nichrome wire because there is no particular mention.

  In addition, the valve gate mold apparatus proposed in Patent Document 2 discloses an embodiment in which a band heater is fitted to the outer peripheral surface of the valve body to keep the material of the material passage in the valve body in a molten state. ing.

Patent Document 3 proposes an injection molding nozzle using a ceramic heater. In this injection molding nozzle, a pair of recesses having a flat bottom surface symmetrical to the central axis of the cylindrical body is formed in the outer peripheral portion of the cylindrical body, and a flat ceramic heater is formed on the bottom surface. It is joined by an adhesive or the like. In addition, an example in which a gate having the same structure as the injection molding nozzle is used as a gate is disclosed.
JP 2000-167845 A (see [0017] [0020]) JP 2006-305850 A (see [0024]) JP 2000-218671 A (see [Summary] [0037])

  The conventional heaters disclosed in Patent Documents 1 and 2 may float from the installation portion due to repeated expansion and contraction related to thermal expansion. For this reason, in particular, it is necessary to retighten the screw portion for attaching the band heater or the like from time to time, and not only the maintenance takes time, but also there is a problem that the mold cannot be used during that time.

  In order to solve the problem, it is conceivable to use a ceramic heater instead of a conventional heater which is relatively inexpensive but easily breaks. However, the nozzle for injection molding disclosed in Patent Document 3 is different from the nozzle for molding a general-purpose resin, so that the silicon nitride can be formed by injection molding of a molding material containing a metal component such as magnesium thixo molding. This is a special nozzle made of quality ceramic. Therefore, in order to prevent the ceramic heater from protruding from the recess due to expansion and contraction due to repeated thermal cycles, a method using a high melting point glass has been proposed as a suitable method for joining the ceramic heater to the recess.

  Therefore, although using a heater that is difficult to break, sprue bushes and gates having the same structure as the injection molding nozzle disclosed in Patent Document 3 lead to cost increase if used in a general-purpose resin molding die. It is difficult to adopt.

  The present invention has been made by paying attention to such a problem, and the object of the present invention is a ceramic that is not easily broken as a heating means that can keep a synthetic resin in a molten state while having a simple structure. An object of the present invention is to provide a sprue bush and a sprue bushing device using a heater.

  In order to solve the above-mentioned problem, the invention of the sprue bush according to claim 1 is a sprue bush installed in a mold for molding a synthetic resin. A cylindrical body in which a flow path is formed and a plate-like body arranged in parallel to the cylindrical body and projecting from the base are formed integrally, and the cylindrical body and the plate-like body are opposed to each other. Each surface to be formed is a flat surface capable of accommodating a ceramic heater.

  According to the first aspect of the present invention, since the surfaces of the cylindrical body and the plate-like body facing each other are formed as flat surfaces, the interval between the flat surfaces is substantially the same as the thickness of the plate-shaped ceramic heater. In this way, the ceramic heater can be accommodated in a close contact state. Then, most of the heat of the ceramic heater is transmitted to the cylindrical body and the plate body. Further, since the cylindrical body and the plate-like body are formed integrally with the base body, most of the heat transmitted to the cylindrical body and the plate-like body is conducted to the base body. Therefore, the heat of the ceramic heater can keep the synthetic resin in the sprue bushing in a molten state with excellent thermal efficiency.

  The invention according to claim 2 is the sprue bush according to claim 1, wherein the plate-like body is formed in the base at at least two locations equidistant from the axis of the cylindrical body. To do.

  According to invention of Claim 2, a ceramic heater can be arrange | positioned in the position of equal intervals from the axial center of a cylindrical body, and the synthetic resin in the flow path of a cylindrical body can be heated evenly. When the plate-like bodies are arranged in two places, the two plate-like bodies are respectively located on opposite sides of the square, and when the plate-like bodies are arranged in four places, the four plate-like bodies are Each will be located on each side of the square. Moreover, when arrange | positioning a plate-shaped body in three places, each of the three plate-shaped bodies will be located in each edge | side of an equilateral triangle.

  According to a third aspect of the present invention, in the sprue bush according to the first or second aspect, a screw insertion hole is formed at a tip of the plate-shaped body, and the cylindrical body at a position corresponding to the hole. Is formed with a screw hole, and a ceramic heater is sandwiched between the plate-like body and the cylindrical body by tightening and fixing the tip of the plate-like body to the cylindrical body using a screw. It is characterized by this.

  According to invention of Claim 3, a ceramic heater can be clamped between each plane which a cylindrical body and a plate-shaped object oppose using the elastic force of a plate-shaped object. Therefore, even if there is a difference in the coefficient of thermal expansion between the plate-like body and the cylindrical body and the ceramic heater, the plate-like body can absorb the displacement caused by the difference by elastic deformation.

  According to a fourth aspect of the present invention, in the sprue bush according to any one of the first to third aspects, the tubular body and the plate-shaped body of the base are provided with a tubular shape on a surface thereof. A heat insulating hole is formed outside the body and the plate-like body.

  According to the fourth aspect of the present invention, when the heat of the base is transmitted from the surface of the base that contacts the mold to the mold side, the amount of heat can be reduced. In addition, when heat is transmitted from the center portion of the base to the outer peripheral portion, the heat insulating hole is an obstacle, and it is difficult for heat to be transmitted.

According to a fifth aspect of the present invention, in the sprue bush according to the fourth aspect, the heat insulating hole is arranged on a circumference concentric with the center of the flow path.
According to the fifth aspect of the present invention, the heat transmitted from the ceramic heater to the plate-like body is transmitted from the root of the plate-like body to the outer peripheral surface side of the base body. To be prevented evenly.

  The invention of the sprue bushing device according to claim 6 is the sprue bushing according to any one of claims 1 to 5, and a ceramic heater sandwiched between the cylindrical body and the plate-like body. It is characterized by comprising.

  According to the invention described in claim 6, since the ceramic heater is sandwiched between the cylindrical body and the plate-like body, a sprue bushing device that is efficiently heated by the ceramic heater is obtained.

  According to the present invention, a sprue bush and a sprue that can be used as a heating means that can keep a synthetic resin in a molten state while having a simple structure, and that can be used as a ceramic heater that is difficult to break, and that can obtain high thermal efficiency. A bushing device can be provided. Moreover, since 2 to 4 ceramic heaters can be used, the number and type of ceramic heaters can be selected in consideration of the heater capacity and the like as necessary.

(First embodiment)
Hereinafter, embodiments of a sprue bush 1 and a sprue bushing device embodying the present invention will be described with reference to FIGS. In addition, although the material of the sprue bush 1 is not specifically limited, steel materials, such as S50C, are used suitably. Further, the sprue bushing device is composed of the sprue bushing 1 and the ceramic heater 10, and it is sufficient that the ceramic heater 10 is appropriately selected from commercially available ones in consideration of the shape, dimensions and heater capacity.

  As shown in FIGS. 1 and 2, the sprue bushing device of the present embodiment is used by being incorporated into a mold 11 for synthetic resin injection molding, and the ceramic heater 10 is provided outside the mold 11 by wiring (not shown). It is connected to a power source so that it can receive power. Similarly, the temperature of the ceramic heater 10 is controlled not to increase more than necessary using a temperature sensor (not shown). The sprue bush 1 is inserted into an opening formed at the center of the fixed-side mounting plate 12 and is fixed to the fixed-side template 13 using a bolt (not shown). A gap is formed between the outer peripheral surface 4b of the plate-like body 4 of the sprue bushing 1 and the inner wall of the hole 13a for loosely fitting the sprue bushing 1 of the fixed-side mold plate 13, and the heat of the plate-like body 4 is fixed. It is difficult to be transmitted to the side mold plate 13. Further, the fitting portion 3 b of the cylindrical body 3 is fitted into the fitting hole 14 a of the mold die 14. The distal end surface 3 a of the cylindrical body 3 faces the cavity 17 formed in the core mold 15 of the movable side mold plate 16 and forms a part of the cavity 17. Note that the sprue bushing device of this embodiment also serves as a direct gate in the mold 11 that does not use a runner.

  As shown in FIG. 2, the sprue bush 1 includes a disc-shaped base body 2, a cylindrical body 3 projecting perpendicularly to the base body 2, a parallel arrangement with the cylindrical body 3, and the base body 2. A pair of plate-like bodies 4 projecting so as to be orthogonal to each other are integrally formed. Two outer planes 3 c of the cylindrical body 3 facing the pair of plate-like bodies 4 are arranged symmetrically with respect to the axis of the cylindrical body 3. Further, an inner plane 4a is formed inside the plate-like body 4 so as to face the outer plane 3c in parallel with the outer plane 3c. The distance between the outer plane 3c and the inner plane 4a is formed substantially the same as the thickness of the ceramic heater 10. Then, if the plate-shaped ceramic heater 10 is accommodated between the outer plane 3 c and the inner plane 4 a and the distal end portion 4 c of the plate-shaped body 4 is fastened and fixed to the cylindrical body 3 using the cross-recessed screw 7. The ceramic heater 10 is sandwiched between the outer plane 3c and the inner plane 4a. A seat surface for the cross-recessed screw 7 is recessed in the distal end portion 4c, and a hole 4d is formed therethrough. A screw hole 3e is formed in the cylindrical body 3 at a position corresponding to the hole 4d.

  In the present embodiment, the outer peripheral surface of the cylindrical body 3 excluding the outer plane 3c positioned axisymmetrically is a plane in a direction orthogonal to the outer plane 3c, and is a rectangular tube shape together with the pair of outer planes 3c. The outer peripheral surface is formed. If the cylindrical body 3 is formed into a rectangular tube shape in this way, the heat capacity of the portion can be reduced, so that the heat of the ceramic heater 10 is spent to efficiently keep the synthetic resin in the flow path 8 in a molten state. It is. The square cylindrical cross-sectional shape is a square.

  The length of the ceramic heater 10 that can be accommodated between the outer plane 3c and the inner plane 4a is limited by the height of the plate-like body 4, but the height of the plate-like body 4 is increased to increase the heating amount. The use of a longer and longer ceramic heater 10 is not appropriate for the sprue bushing 1 of this embodiment. This is because the synthetic resin in the tapered hole 9 of the cylindrical body 3 is not brought into a molten state, and the reason will be described below.

  If the sprue bushing device of this embodiment is used, even if the nozzle of the injection molding machine is always in contact with the nozzle receiving surface 5, the temperature at the nozzle tip does not drop, so the synthetic resin in the nozzle is kept in a molten state. The molten synthetic resin is always injected. However, the synthetic resin present in the tapered hole 9 of the fitting portion 3b of the cylindrical body 3 needs to be cooled at the same time as cooling the molded product for each shot of injection molding. For this purpose, the fitting portion 3b can extract the sprue together with the molded product when the molded product is taken out without disposing the ceramic heater 10 as a non-heated portion. Then, the next shot is performed when the melted synthetic resin fills the tapered hole 9 that has been taken out of the sprue and becomes a cavity.

  As shown in FIGS. 2 and 3, the mounting surface 2a of the base 2 for mounting the sprue bush 1 to the stationary mold plate 13 of the mold 11 is provided on the outside of the cylindrical body 3 and the plate-like body 4 and on the cylindrical side. A total of eight heat-insulating holes 6 are formed on the circumference concentric with the axis of the body 3 to a depth not more than half the thickness of the base 2. The presence of the heat insulating hole 6 reduces the contact area of the mounting surface 2a with the fixed-side mold plate 13 and restricts the movement of heat from the base of the plate-like body 4 toward the outer periphery of the base 2. . As shown in FIGS. 2 and 4, two bolt holes 2 c are formed in the base 2, and a seating surface is formed from the surface 2 b of the base 2 in order to accommodate the heads of the bolts inserted through the bolt holes 2 c. 2d is recessed. The bolt hole 2c also restricts the movement of heat in the base body 2 to the outer peripheral side, like the heat insulating hole 6.

  As shown in FIG. 5, at the center of the sprue bush 1, a straight circular hole 8 communicating between the nozzle receiving surface 5 and the tip surface 3a and a tapered hole that expands outward. 9 is formed. As described above, the synthetic resin in the flow path 8 is always kept in a molten state by receiving heat from the ceramic heater 10, and the synthetic resin remaining in the tapered hole 9 after injection changes from a molten state to a softened state with time. Thus, the hardness can be taken out from the mold 11 together with the molded product after the cooling time.

  In the sprue bushing device of this embodiment, two ceramic heaters 10 having a heater capacity of 100 V and 40 W are used so that the synthetic resin in the flow path 8 having a diameter of 3 mm can always be kept in a molten state.

Therefore, according to the above embodiment, the following effects can be obtained.
(1) In the embodiment described above, the plate-shaped ceramic heater 10 can be accommodated between the outer flat surface 3 c of the cylindrical body 3 and the inner flat surface 4 a of the plate-shaped body 4. Therefore, most of the heat of the ceramic heater 10 can be transmitted to the cylindrical body 3 and the plate-like body 4. In addition, since the cylindrical body 3 and the plate-like body 4 and the base body 2 are integrally formed, most of the heat transferred to the cylindrical body 3 and the plate-like body 4 can be conducted to the base body 2. Therefore, it is possible to provide the sprue bush 1 that can keep the synthetic resin in the flow path 8 in a molten state with high thermal efficiency.

  (2) In the above embodiment, since the ceramic heater 10 can be arranged at two positions equidistant from the axial center of the cylindrical body 3, the synthetic resin in the flow path 8 of the cylindrical body 3 is heated evenly. The sprue bush 1 which can be provided can be provided.

  (3) In the above embodiment, the plate-like ceramic heater 10 accommodated between the outer flat surface 3c and the inner flat surface 4a can be sandwiched by screwing the front end 4c of the plate-like member 4 to the cylindrical member 3. I made it. Therefore, even if there is a difference in thermal expansion coefficient between the plate-like body 4 and the cylindrical body 3 and the ceramic heater 10, it is possible to provide the sprue bush 1 that can absorb the deviation caused by the difference.

  (4) In the above embodiment, a total of eight heat insulating holes 6 are formed in the mounting surface 2 a of the base 2. Therefore, when the heat of the base 2 is transmitted from the surface where the base 2 and the mold 11 abut to the mold 11 side, the amount of heat can be reduced. Further, when heat is conducted from the central portion of the base 2 to the outer peripheral portion, the heat insulating hole 6 becomes an obstacle, so the amount of conduction heat is reduced. Accordingly, the heat of the ceramic heater 10 can be used efficiently in order to maintain the molten state of the synthetic resin in the flow path 8.

(Second Embodiment)
Next, a sprue bush 61 according to a second embodiment that embodies the present invention will be described with reference to FIGS. 7 and 8, focusing on portions different from the first embodiment. The sprue bush 61 of the present embodiment is different in the shape of the cylindrical body 63 and the number of the plate-like bodies 64 from the shape of the cylindrical body 3 and the number of the plate-like bodies 4 in the sprue bush 1, and the other parts are the same. .

  As shown in FIG. 7, the outer peripheral surface of the cylindrical body 63 is formed in a shape in which the corners of an equilateral triangle forming three sides by three outer planes 63a are chamfered by an arc 63b of the same circle. Three plate-like bodies 64 are arranged at positions facing the three outer planes 63a, and an inner plane 64a is formed inside the plate-like body 64 in parallel with the outer plane 63a. Similar to the sprue bush 1 in the first embodiment, the distance between the outer plane 63a and the inner plane 64a is formed to be substantially the same as the thickness of the ceramic heater 10.

  In the sprue bush 61 having such a structure, since three ceramic heaters 10 can be used, the heater capacity is higher than that of the sprue bush 1. Therefore, when molding a synthetic resin having a relatively high melting point, the synthetic resin can be kept in a molten state in the flow path 8 without using a relatively expensive heater with an increased watt density.

And in this 2nd Embodiment, in addition to the effect in 1st Embodiment, the following effects can be acquired.
(5) In the above embodiment, three ceramic heaters 10 can be used. For this reason, the same calorific value as that obtained when the heater capacity is increased without increasing the watt density can be provided, so that the sprue bushing 61 capable of keeping a synthetic resin having a relatively high melting point in a molten state can be provided. Further, in order to keep a synthetic resin having a particularly low melting point in a molten state, it is possible to use the ceramic heater 10 having a reduced watt density. Therefore, it is possible to provide an inexpensive sprue bush 61 with few failures.

(Third embodiment)
Next, a sprue bush 71 according to a third embodiment embodying the present invention will be described with reference to FIG. 9 with a focus on differences from the first embodiment and the second embodiment.

  As shown in FIG. 9, the sprue bushing 71 of the present embodiment is different from the sprue bushing 1 in that the plate-like body 74 is erected at four locations on the base body 2, but has a square cylindrical outer peripheral surface. The point which uses the cylindrical body 73 is similar, and the other part is the same. However, the four outer flat surfaces 73a corresponding to each side of the square cross-sectional shape are all processed into smooth surfaces so that a sufficient contact area with the ceramic heater 10 is ensured.

  An inner plane 74a is formed inside each plate-like body 74 in parallel with the outer plane 73a. Similar to the sprue bushes 1 and 61 in the first and second embodiments, the distance between the outer flat surface 73a and the inner flat surface 74a is formed substantially the same as the thickness of the ceramic heater 10.

  Since the four ceramic heaters 10 can be used in the sprue bushing 71 having such a structure, when molding a synthetic resin having a relatively high melting point, as with the sprue bushing 61, a relatively expensive watt density. The synthetic resin can be kept in a molten state in the flow path 8 without using a heater with a raised height.

In the third embodiment, the following effects can be obtained in addition to the effects in the first and second embodiments.
(6) In the above embodiment, four ceramic heaters 10 can be used. For this reason, the same calorific value as that obtained when the heater capacity is increased without increasing the watt density can be provided, so that the sprue bushing 71 capable of keeping a synthetic resin having a relatively high melting point in a molten state can be provided. Also, in order to keep a synthetic resin having a particularly low melting point in a molten state, the ceramic heater 10 having a reduced watt density can be used, so that an inexpensive sprue bushing 71 with few failures can be provided.

(Example of change)
In addition, you may change the said embodiment as follows.
In the above embodiment, the flow path 8 and the taper hole 9 are formed in the center of the cylindrical body 3 so that the sprue bushes 1, 61, 71 also serve as a direct gate, but the taper hole 9 is not provided. Only the path 8 may be configured so that the synthetic resin can be injected into the runner in the mold 11.
In the above embodiment, the sprue bushes 1, 61, 71 also serve as a direct gate. However, instead of the tapered hole 9, a small-diameter hole may be formed in the tip surface 3a to form a pin gate.
In the above embodiment, the total number of the heat insulating holes 6 is 8. However, the number may be changed after appropriately selecting the inner diameter and depth of the heat insulating holes 6. Further, the heat insulating holes 6 may be provided on a plurality of circumferences having different diameters without being arranged on the same circumference.

Sectional drawing of the metal mold | die incorporating the sprue bush which is embodiment of this invention. The front view of the sprue bush of 1st Embodiment. The top view of the sprue bush of 1st Embodiment. The bottom view of the sprue bush of 1st Embodiment. Sectional drawing of the AA arrow in FIG. The perspective view of the sprue bush of 1st Embodiment. Sectional drawing which shows typically the cylindrical body and plate-shaped body of 2nd Embodiment. The perspective view of the sprue bush of 2nd Embodiment. Sectional drawing which shows typically the cylindrical body and plate-shaped body of 3rd Embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1,61,71 ... Sprue bush, 2 ... Base | substrate, 3,63,73 ... Cylindrical body, 3e ... Screw hole, 4,64,74 ... Plate-like body, 4c ... Tip part, 4d, 13a ... Hole, 6 ... heat insulation hole, 8 ... flow path, 10 ... ceramic heater, 11 ... mold.

Claims (6)

  In a sprue bush installed in a mold for synthetic resin molding, a plate-shaped base, a cylindrical body protruding from the base and having a flow path of molten resin, and arranged parallel to the cylindrical body And a plate-like body projecting from the base is integrally formed, and each surface of the cylindrical body and the plate-like body facing each other is formed as a flat surface capable of accommodating a ceramic heater. Sprue bush characterized by   2. The sprue bush according to claim 1, wherein the plate-like body is formed in at least two places at equal intervals from the axis of the cylindrical body in the base body.   A screw insertion hole is formed at the tip of the plate-like body, and a screw hole is formed in the cylindrical body at a position corresponding to the hole, and the tip of the plate-like body is formed using a screw. The sprue bush according to claim 1 or 2, wherein a ceramic heater is sandwiched between the plate-like body and the tubular body by being fastened and fixed to the tubular body.   The heat insulation hole located in the outer side of the cylindrical body and plate-shaped body is formed in the surface which the said cylindrical body and the said plate-shaped body of the said base | substrate project. 4. The sprue bush according to any one of 3.   The sprue bush according to claim 4, wherein the heat insulation hole is arranged on a circumference concentric with the center of the flow path.   A sprue bushing device comprising: the sprue bushing according to any one of claims 1 to 5; and a ceramic heater sandwiched between the cylindrical body and the plate-like body.

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