JP2003191291A - Valve gate type mold apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent lowering of characteristics of a resin by decreasing temper ature difference of the resin in a material path in a valve device and preventing generation of a locally excessively high temperature part. <P>SOLUTION: A linear heater 40 for heating a valve main body 1 is fitted on the outer peripheral face of the valve main body 1 in such a way that doubly folded one is wound into a cylindrical coil-like shape. By linearly extending an apex folded part 42a of the linear heater 40, a connecting part 45 being extended to an apex part of a casing 2 is formed and by opening the apex folded part 42a, an arc-shaped folded part 46 to be fitted on the apex outer peripheral face 1a of the valve main body 1 is formed. In this arrangement, an intermediate part in the axial direction of the valve main body 1 is heated by means of the linear heater 40 and in addition, it is heated by means of the arc-shaped folded part 46 of the linear heater 40. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a valve gate type mold apparatus used for injection molding of thermoplastic resin.

[0002]

In a hot runner die apparatus for heating a resin, which is a molding material in a material passage to a gate to a product cavity, to constantly keep a molten state,
2. Description of the Related Art A valve gate type mold device is known in which a gate is mechanically opened and closed by a valve pin. The hot runner mold device is intended to increase the molding efficiency, and the gate is closed to prevent the resin from leaking from the gate when the mold is opened.

FIG. 4 (a) shows an example of a valve body 1 of a valve device in a valve gate type mold device of this type. In the figure, reference numeral 2 denotes a cylindrical casing, which is connected to a manifold (not shown) located on the left side of the figure and is formed on the main body portion 3 of a mold body such as a stationary mold plate. It is to be inserted into the formed hole 4. The casing 2 has a fixing ring 7 which is a fixing member fixed to the flange portion 5 on the end portion on the manifold side and the outer peripheral surface of the end portion on the opposite gate 6 side.
Are supported by the body portion 3 of the mold body by being fitted in the hole portion 4, and in other portions, a heat insulating layer is formed between the valve body 1 and the body portion 3 of the mold body. A gap is formed. The inside of the casing 2 is a material passage 8 communicating with the gate 6. A valve pin (not shown) that penetrates the material passage 8 and moves in the left-right direction in the drawing to open and close the gate is provided. Also,
A heater 9 that heats the resin in the material passage 8 is provided on the outer peripheral surface of the casing 2, and a cylindrical heater cover 10 that covers the heater 9 from the outer peripheral side is fixed. The heater 9 is composed of a linear heater and is wound around the outer peripheral surface of the casing 2. The heater 9 is tightly wound on both ends of the casing 2, but is coarsely wound on the intermediate portion. For the reason,
It will be described later. The number of turns of the heater 9 is two on the manifold side and three on the gate 6 side.

FIG. 4B shows the result of measuring the temperature in the material passage 8. In the graph of the figure,
The horizontal axis represents the distance from the tip of the valve body 1 on the gate 6 side, and the vertical axis represents the temperature. The temperature was measured at each point indicated by a black circle in the material passage 8. And the dashed graph
a1 and a2 are the results when the set temperature for control of the valve body 1 and the manifold is set to 300 ° C. The solid line graphs b1 and b2 are the results when the set temperature is set to 250 ° C and the dotted line graphs. c1 and c2 are the results when the same set temperature is set to 200 ° C. The mold cooling temperature is 10 ℃
Set to.

As is clear from the graphs a1, b1 and c1, the temperature tends to be low at both ends of the valve body 1 and high at the central portion. It is considered that this is because heat is transferred from both ends in the central portion. Further, the valve body 1 is in contact with the body portion 3 of the mold body that is cooled in order to quickly solidify the resin in the product cavity only at both ends. It is thought that another cause is that heat is released to the body portion 3 of the body. In the illustrated valve device, in order to eliminate such non-uniformity of temperature, the heater 9 is tightly wound on both end sides of the valve body 1 and roughly wound in the middle portion.
Nevertheless, as the measurement results show, the temperature distribution is highly non-uniform.

At the lowest temperature portion of the material passage 8, that is, at both ends, it is necessary to obtain a temperature at which the fluidity of the resin can be ensured. Therefore, the temperature of the intermediate portion becomes excessively high. When the temperature is too high, the resin in the material passage 8 is burned (causing black charring), and the characteristics of this resin deteriorate.

The present invention is intended to solve such a problem, and an object of the present invention is to provide a valve gate type mold apparatus capable of reducing the temperature difference of the molding material in the material passage of the valve apparatus.

[0008]

A valve gate type mold apparatus according to the invention of claim 1 is provided with a plurality of molds which are opened and closed to form product cavities between them when the molds are closed. A valve device for opening and closing a gate for communicating a material passage with the product cavity, the valve device comprising:
The valve body has a valve body held and incorporated in a hole formed in the body portion of the mold body, and a material passage communicating with the gate is formed in the valve body, and a coil is formed on the outer peripheral portion of the valve body. A wound linear heater is provided, and the tip of the linear heater is extended to the axial tip of the valve body located on the gate side.

At the time of molding, a plurality of mold bodies are closed to form a product cavity between these mold bodies, a gate is opened, and a molding material is filled from the material passageway through the gate into the product cavity. Then, the gate is closed by the valve device, and after the molding material in the product cavity is solidified, the mold is opened to take out the molding material in the product cavity, that is, the molded product. After that, the mold is closed again and the above molding cycle is repeated. Throughout the entire molding cycle, the molding material in the material passage of the valve body is always kept in a molten state by the heating of the linear heater. Here, since the valve body is uniformly heated by the linear heater from the axially intermediate portion to the axially tip portion, the temperature difference of the molding material in the material passage of the valve body is reduced.

According to a second aspect of the invention, in the valve gate mold apparatus according to the first aspect of the invention, the linear heater is 2
It is formed by folding back in a three-fold manner and further winding it in a coil shape, and the leading end folding portion is extended to the axial leading end portion of the valve body.

By folding back two linear heaters for heating the valve body, the amount of heat generated per unit length of the entire heater increases.

According to a third aspect of the present invention, in the valve gate mold apparatus according to the second aspect of the invention, the linear heater is formed in a cylindrical coil shape along the outer peripheral portion of the valve body, and the tip end portion thereof is formed. To form a connecting portion extending from the valve body to the axial tip portion of the valve body, and an arc-shaped bent portion having an arc shape so that the tip folded portion of the linear heater is along the tip outer peripheral portion of the valve body. It was formed.

The linear heater makes good contact with the outer periphery of the intermediate portion of the valve body and the outer periphery of the distal end of the valve body, and the contact is secured.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION A first embodiment of a valve gate type mold apparatus of the present invention will be described below with reference to FIGS. In the following description, the same parts as those in FIG. 4A described above are designated by the same reference numerals. 11 is a fixed type and 12 is a movable type. The fixed type 11 and the movable type 12, which are mold bodies, move in the vertical direction (the mold opening / closing direction) shown in FIG. The product cavity 13 having a product shape is formed. The fixed mold 11 is a fixed mold plate 3 made of metal as its main body.
And a fixed side mounting plate (not shown) fixed to the back side of the fixed side template 3 via a spacer block, and between the fixed side mounting plate and the fixed side template 3. Is provided with a manifold 16. This manifold 16 has a runner 17 that is a material passage formed inside, and the thermoplastic resin that is the molding material in this runner 17 is always in a molten state by the heating of a heater (not shown) provided in the manifold 16. It is designed to be kept at. The fixed mold plate 3 may be composed of a plurality of members in addition to a fixed receiving plate or a gate bush. Further, a hole 4 is formed through the fixed-side mold plate 3, and the tip of the hole 4 on the side of the movable mold 12 is a gate 6 communicating with the product cavity 13.

Further, a valve device 21 for opening and closing the gate 6 is incorporated in the fixed mold 11. Next, the configuration of the valve device 21 will be described. A valve body 1 whose axial direction is the mold opening / closing direction is incorporated in the hole 4 of the stationary mold plate 3. Most of the valve body 1 is composed of a cylindrical casing 2. One end of the casing 2 is a flange portion 5 which is fixed and supported between the manifold 16 and the fixed side mold plate 3. ing. At the same time, the flange portion 5 is fitted in the step portion 23 formed at the end of the hole portion 4 on the manifold 16 side. A fixing ring 7 is fitted and fixed to the outer peripheral surface of the end of the casing 2 on the gate 6 side, and the fixing ring 7 is a cylindrical fitting surface formed in the hole 4. It is fitted with 24. As a result, the portion of the casing 2 on the gate 6 side is supported by the fixed-side template 3. As described above, the valve body 1 is in contact with the fixed-side template 3 at both end portions, but is a fixing member between the outer surface of the valve body 1 and the inner surface of the hole portion 4 in other portions. First and second gaps 25, 26 that are blocked by the fixing ring 7 are formed. This first and second gap
The fixing ring 7 causes the first gap 25 located on the gate 6 side of the fixing ring 7 to be located at the gate 6 by the fixing ring 7.
The fixing ring 7 blocks the inflow of resin into the second gap 26, which serves as an air heat insulating layer.

Further, the inside of the casing 2 serves as a material passage 8 for communicating the runner 17 in the manifold 16 with the gate 6. The material passage 8 has a substantially columnar shape with the mold opening / closing direction as the axial direction, but the end on the runner 17 side is a bent portion 31. The bent portion 31 is formed by embedding the insert 32 in the casing 2. Also, the gate 6 in the material passage 8
Three or more support blades 33 extending in the mold opening / closing direction are formed on the inner peripheral surface of the tip end portion on the side.

Further, a linear heater 40, which is a heating means for heating the material passage 8, is provided on the outer peripheral surface of the casing 2, and the linear heater 40 is provided on the outer peripheral side by a cylindrical heater cover 10 made of metal. Are covered from. Also,
As shown in FIG. 3, the linear heater 40 has a non-heat generating portion 41b at the base end of the heat generating portion 41a. And the heat generating part 41a
Is folded in two and wound on a cylindrical coil so as to fit on the outer peripheral surface of the casing 2. The heating part
The linear heater 40 is densely wound on both end sides of 41a, but the linear heater 40 is roughened in the central portion with a pair of aluminum coil spacers 43 interposed.
This is to prevent the temperature in the central portion from becoming excessively higher than the temperature in the peripheral portion. Also, the linear heater 40
Includes a heating wire made of nichrome wire or the like (not shown) inside the outer tube 44 made of stainless steel coaxially, and a powdery magnesia (illustrated as an insulating material between the heating wire and the outer tube 44). No) is interposed. Further, the tip end turnback portion 42a of the heat generating portion 41a forms a linearly extending connecting portion 45 to extend from the tip end of the casing 2 to the tip end portion of the valve body 1, and the tip end side of the connecting portion 45 is horizontally oriented. It is bent to. Here, the tip turn-back portion 42a bent in the horizontal direction
Since the heat generating portion 41a is folded back in two layers, the tip folding portion 42a is opened in an arc shape so as to be fitted to the tip outer peripheral surface 1a of the valve body 1 and the tip outer peripheral surface 1a of the valve body 1 is opened.
An arc-shaped bent portion 46 for heating the is formed. A step groove 47 that fits the arc-shaped bent portion 46 is formed on the outer peripheral surface 1a of the distal end of the valve body 1 in which the arc-shaped bent portion 46 is mounted, and the step portion groove 47 communicates with the step-shaped groove 47 to connect the connecting portion 45. A groove portion 48 is formed inside the fixing ring 7. Further, a cover portion 7A is formed on the bottom of the fixing ring 7 to cover the front end folded portion 42a of the heat generating portion 41a. Although not shown, the casing 2 is provided with a temperature sensor along the inside of the linear heater 40.

The casing 2 incorporates a valve pin 36 as a valve body which moves in the mold opening / closing direction by driving a driving device such as a hydraulic cylinder device (not shown) provided on the fixed side mounting plate. The valve pin 36 closes the gate 6 by a gate closing portion 37 formed at the tip end on the gate 6 side being removably fitted into the gate 6. Further, the valve pin 36 has the mold opening / closing direction as an axial direction, and the support blade 33 of the casing 2 is provided.
The outer peripheral surface is always slidably in contact with the inner edge of the. As a result, the tip of the valve pin 36 on the gate 6 side is supported. Further, the valve pin 36 is supported at the end of the valve body 1 on the manifold 16 side by a guide bush 38 fixed in the insert 32. That is, the valve pin 36 slidably penetrates through the guide bush 38. In order to connect the valve pin 36 to the drive device provided on the fixed side mounting plate,
36 also penetrates through holes 39 formed in the manifold 16.

Reference numeral 50 denotes a movable side mold plate of the movable mold 12, and the movable side mold plate 50 forms the product cavity 13 together with the fixed side mold plate 3.

Although not shown, the stationary mold plate 3 and the movable mold plate 50 are provided with fluid passages for passing a cooling fluid such as water for cooling the product cavity 13.

Next, the operation of the above configuration will be described. First, the fixed mold 11 and the movable mold 12 are closed, a product cavity 13 is formed between the fixed mold 11 and the movable mold 12, and then the valve pin 36 is separated from the movable mold 12 as shown by a chain line in FIG. And the gate 6 is opened.
Then, a molten thermoplastic resin, which is a thermoplastic molding material, is injected into the fixed mold 11 from the injection molding machine. This resin passes through the runner 17 of the manifold 16, the material passage 8 in the valve body 1, and the support blades 33 in which the valve pin 36 is fitted, and then the resin from the gate 6 to the product cavity 13
Flows in. After the resin is filled in the product cavity 13 as described above, the pressure is maintained, and the valve pin 36 moves toward the movable die 12 as shown by the solid line in FIG. Gate 6 is closed. The resin in the product cavity 13 is positively cooled by the cooling fluid passing through the fluid passage. Then, after the resin in the product cavity 13 is cooled and solidified, the fixed mold 11 and the movable mold 12 are opened, and the resin in the product cavity 13, that is, the molded product is taken out. After that, the mold is closed again and the above molding cycle is repeated.
Like the resin in the runners 17 of the resin 16, the resin in the material passage 8 of the valve body 1 has a linear heater 40 wound around the outer periphery of the valve body 1 and the outer peripheral surface 1a of the tip of the valve body 1.
The arc-shaped bent portion 46 formed on the tip-turned-back portion 42a of the linear heater 40 wound around is constantly kept in a molten state.

As described above, in the valve body 1,
Originally, the temperature tends to be higher at the central portion in the axial direction than at both ends, but in the present embodiment, the valve body 1 has its outer peripheral portion heated by the linear heater 40, and the tip of the valve body 1 is further heated. By heating the outer peripheral surface 1a by the arc-shaped bent portion 46 formed in the tip folded portion 42a of the linear heater 40, the valve body 1 is heated substantially uniformly from the axial middle portion to the axial tip portion of the valve body 1. To do. This reduces the temperature difference of the resin in the material passage 8 of the valve body 1. Therefore, in order to ensure the fluidity of the resin in the material passage 38, it is possible to prevent a portion of the material passage 8 where the temperature of the resin becomes excessively high, and it is possible to prevent the resin from being burned. It is possible to prevent deterioration of the characteristics of this resin.

Here, the result of measuring the temperature in the material passage 8 will be described with reference to the graph of FIG.
Although the same figure has already been described, in the graph of the figure, the horizontal axis represents the distance from the tip of the valve body 1 on the gate 6 side, and the vertical axis represents the temperature. The temperature is measured in the material passage 8
It carried out about each point shown by the black circle inside. The broken line graphs a1 and a2 show the results when the set temperature for control of the valve body 1 and the manifold is set to 300 ° C, and the solid line graphs b1 and b2 show the case when the set temperature is set to 250 ° C. As a result, the dotted line graphs c1 and c2 are the results when the same set temperature was set to 200 ° C. Also, thin line graphs a1, b1,
c1 is the result of the conventional mold device without the arc-shaped bent portion 46 for heating the tip portion of the valve body 1, and the thick line graph a2,
b2 and c2 are arc-shaped bent portions that heat the tip of the valve body 1.
It is a result of the mold apparatus of this embodiment provided with 46. The mold cooling temperature was set to 10 ° C.

When there is no arc-shaped bent part 46 for heating the tip of the valve body 1 (graphs a1, b1, c1) and the arc-shaped bent part
Comparing with the case with 46 (graphs a2, b2, c2), the temperature difference between the axially intermediate portion of the valve body 1 and the tip side is smaller in the case with the arc-shaped bent portion 46. It is clear that the temperature distribution in the material passage 8 is more uniform.

Further, the linear heater 40 has two heating parts 41a.
Since it is folded back in a heavy fold and wound around the outer peripheral surface of the valve body 1 in a coil shape, the watt density of the entire linear heater 40 can be increased and the amount of heat generation per unit length can be increased. As a result, the entire linear heater 40 can be made thinner,
This is advantageous in incorporating the linear heater 40 in the limited space in the mold. Further, since the tip end folded-back portion 42a of the linear heater 40 is expanded in an arc shape to heat the tip outer peripheral surface 1a of the valve body 1, the casing 2 of the valve body 1 is heated by one continuous linear heater 40. To the outer peripheral surface 1a of the tip of the valve body 1 can be uniformly heated. Therefore, it is not necessary to separately provide a heater for heating the casing 2 of the valve body 1 and the tip outer peripheral surface 1a of the valve body 1. Furthermore, linear heater
Since the outer tube 44 covering 40 is made of metal, it can maintain the shape along the outer peripheral surface of the valve body 1 when wound in a cylindrical coil shape, and the valve body 1 can be attached to the valve body 1 in a linear shape. Assembly work of the heater 40 is also easy. Further, by forming the cover portion 7A on the fixing ring 7 so as to cover the front end folded portion 42a of the linear heater 40, the linear heater 40 and the molten thermoplastic resin do not come into contact with each other. Therefore, the thermal effect of the linear heater 40 due to the molten thermoplastic resin can be suppressed, and the linear heater 40 due to heat can be suppressed.
Can be prevented from deteriorating.

The present invention is not limited to the above embodiment, and various modifications can be made. For example,
The basic structure of the valve gate type mold device and the number of windings of the linear heater 40 to be assembled in the valve body are not limited to those in the above embodiment, and may be appropriately selected.

[0027]

According to the valve gate mold apparatus of the first aspect of the present invention, the linear heater can heat the valve body substantially uniformly from the axial central portion of the valve body to the axial distal end portion of the valve body. The temperature difference of the resin in the material passage of the valve body can be reduced. Therefore, it is possible to prevent a portion where the temperature of the resin locally becomes excessively high in the material passage, and prevent the resin from being burned.
It is possible to prevent the characteristics of the resin from being deteriorated and prevent the characteristics of the molding material from being deteriorated.

According to the valve gate type mold apparatus of the invention of claim 2, in addition to the effect of claim 1, the heat generation amount per unit length of the entire heater is increased, and the entire linear heater can be made thin and linear. The heater can be installed in the limited space in the mold.

According to the valve gate mold apparatus of the second aspect of the invention, in addition to the effect of the second aspect, the linear heater is surely contacted from the central portion in the axial direction of the valve body to the distal end portion in the axial direction of the valve body. Thus, the valve body can be efficiently heated, and the work of assembling the linear heater to the valve body becomes easy.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing a first embodiment of a valve gate type mold device of the present invention.

FIG. 2 is an enlarged sectional view of a gate portion of the same.

FIG. 3 is a perspective view of the same linear heater.

4A and 4B show temperature measurement results, where FIG. 4A is a vertical cross-sectional view of a valve device, and FIG. 4B is a graph showing temperature.

[Explanation of symbols]

1 valve body 1a Tip outer peripheral surface 3 Fixed side template (main body) 4 holes 8 material passage 11 Fixed type 12 Movable type 13 Product cavity 17 Runner (material passage) 21 valve device 25,26 First and second gap 40 linear heater 42a Tip folding part 46 Arc-shaped bend

Claims (3)

[Claims] 1. A plurality of molds which are opened and closed to form product cavities between them when the molds are closed, and a valve device which opens and closes a gate for communicating a material passage provided in the molds with the product cavities. The valve device has a valve main body held and incorporated in a hole formed in the main body of the mold body, forms a material passage communicating with the gate in the valve main body, and A valve gate mold, wherein a linear heater wound in a coil shape is provided on an outer peripheral portion, and a tip portion of the linear heater is extended to an axial tip portion of the valve body located on the gate side. apparatus. 2. The linear heater is formed by folding back two wires and further winding them in a coil shape, and having a tip-turning portion thereof extended to an axial tip portion of the valve body. The valve gate mold apparatus according to claim 1. 3. The linear heater is formed into a cylindrical coil shape along the outer peripheral portion of the valve body, and a connecting portion extending from the tip portion to the axial tip portion of the valve body is formed. 3. The valve gate mold apparatus according to claim 2, wherein an arc-shaped bent portion is formed so that the bent-back portion of the linear heater extends along the outer peripheral portion of the distal end of the valve body.