JP3709843B2 - Valve gate type mold equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a valve gate mold apparatus used for injection molding of a thermoplastic resin.
[0002]
[Problems to be solved by the invention]
In a hot runner mold apparatus that heats the resin that is the molding material in the material passage to the gate to the product cavity and keeps it in a molten state at all times, a valve gate mold apparatus that mechanically opens and closes the gate with a valve pin is known. ing. The hot runner mold apparatus 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.
[0003]
FIG. 4 ( A ) shows an example of the valve body 1 of the valve device in this type of valve gate mold apparatus. In the figure, reference numeral 2 denotes a cylindrical casing. The casing 2 is connected to a manifold (not shown) located on the left side of the figure, and is formed on a main body 3 of a mold body such as a fixed side template. It is inserted into the hole 4 made. In the casing 2, the flange 5 at the end on the manifold side and the fixing ring 7 which is a fixing member fixed to the outer peripheral surface of the end on the opposite gate 6 are fitted in the hole 4. As a result, it is supported by the main body portion 3 of the mold body, and a gap forming a heat insulating layer is formed between the valve main body 1 and the main body portion 3 of the mold body in other portions. Further, the inside of the casing 2 is a material passage 8 communicating with the gate 6. A valve pin (not shown) that passes through the material passage 8 and moves in the horizontal direction in the drawing to open and close the gate is provided. 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 a linear heater and is wound around the outer peripheral surface of the casing 2. The heater 9 is densely wound on both end sides of the casing 2, but is roughly wound on the intermediate portion. The reason will be described later. The number of turns of the heater 9 is 2 on the manifold side and 3 on the gate 6 side.
[0004]
FIG. 4B shows the result of measuring the temperature in the material passage 8. In the graph of the figure, the horizontal axis is the distance from the tip of the valve body 1 on the gate 6 side, and the vertical axis is the temperature. The temperature was measured for each point indicated by a black circle in the material passage 8. 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. The solid line graphs b1 and b2 show the results when the set temperature is set to 250 ° C. As a result, dotted line graphs c1 and c2 are the results when the set temperature is set to 200 ° C. The mold cooling temperature was set to 10 ° C.
[0005]
As is apparent 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 center. This is considered to be due to heat being transmitted from both ends in the central portion. In addition, the valve body 1 is in contact with only the both ends of the mold body 3 which is cooled in order to quickly solidify the resin in the product cavity. It is thought that another cause is that the heat escapes to the main body 3 of the body. In the illustrated valve device, in order to eliminate such temperature non-uniformity, the heater 9 is tightly wound at both ends of the valve body 1 while being roughly wound at the intermediate portion. As shown, the non-uniformity of temperature distribution is large.
[0006]
It is necessary to obtain a temperature that can ensure the fluidity of the resin at the lowest temperature portion of the material passage 8, that is, at both ends, but the temperature of the intermediate portion becomes excessively high. If the temperature is too high, the resin in the material passage 8 is burnt (causes black scorch), and the properties of the resin deteriorate.
[0007]
An object of the present invention is to provide a valve gate mold apparatus capable of reducing the temperature difference of molding materials in a material passage of a valve apparatus.
[0008]
[Means for Solving the Problems]
The valve gate mold apparatus according to the first aspect of the present invention communicates a plurality of molds that open and close each other and form a product cavity therebetween when the mold is closed, and a material passage provided in the mold body. and a valve device for opening and closing the gate, the valve device has a valve body that is embedded and held in the mold body in the hole formed in the body portion, communicating with the gate to the valve body molding to form a material passage of material, the valve in the valve gate type mold apparatus provided with a linear heater coiled on the outer periphery of the body, the linear covered from the outer side by the heater cover made of metal The heater is folded back into two layers, and the linear heater folded back into the two layers is formed in a cylindrical coil shape along the outer periphery of the valve body, and folded into the two layers. The returned linear heater is formed with a connecting portion extending from the tip portion to the tip portion in the axial direction of the valve body, and the tip turn-up portion of the linear heater extends along the outer peripheral surface of the tip end of the valve body. Thus, it is opened in an arc shape to form an arc-shaped bent portion .
[0009]
At the time of molding, a plurality of molds are closed to form product cavities between the molds, the gate is opened, and the molding material is filled into the product cavities from the material passage through the gates. Next, 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. Thereafter, 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, the valve body is uniformly heated by the linear heater from the axial middle part to the axial tip part, so that the temperature difference of the molding material in the material passage of the valve body is reduced.
[0010]
Moreover, the amount of heat generated per unit length of the entire heater is increased by folding back two linear heaters for heating the valve body.
[0011]
Furthermore, the amount of heat generated per unit length of the entire heater is increased by folding back two linear heaters for heating the valve body.
[0012]
According to a second aspect of the present invention, in the valve gate mold apparatus according to the first aspect of the present invention, a fixing ring is fitted and fixed to the outer peripheral surface of the tip end portion on the gate side of the valve body. The fixing ring is fitted with a cylindrical fitting surface formed in the hole, and a cover portion is formed to cover the arc-shaped bent portion, and between the outer surface of the valve body and the inner surface of the hole. First and second gaps that are blocked by the fixing ring are formed, and the first gap is a heat insulating layer that communicates with the gate and into which the molding material flows, and the second gap is an air insulation. Is a layer .
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a first embodiment of the valve gate mold apparatus of the present invention will be described with reference to FIGS. In the following description, the same reference numerals are given to the portions common to FIG. 4A described above. 11 is a fixed mold, 12 is a movable mold, and these fixed mold 11 and movable mold 12 which are mold bodies move to each other in the illustrated vertical direction (mold opening / closing direction) in FIG. A product cavity 13 having a product shape is formed. The fixed mold 11 includes a metal fixed-side mold plate 3 as a main body, and a fixed-side mounting plate (not shown) fixed to the back side of the fixed-side mold plate 3 via a spacer block. A manifold 16 is provided between the fixed side mounting plate and the fixed side mold plate 3. The manifold 16 has a runner 17 that is a material passage formed therein, and the thermoplastic resin that is a molding material in the runner 17 is always melted by heating of a heater (not shown) provided in the manifold 16. To be kept. The fixed-side template 3 may be constituted by a plurality of members by adding a fixed-side receiving plate or a gate bush. Further, a hole 4 is formed through the fixed mold 3, and the tip of the hole 4 on the movable mold 12 side is a gate 6 that communicates with the product cavity 13.
[0014]
Further, the fixed mold 11 incorporates a valve device 21 for opening and closing the gate 6. Next, the configuration of the valve device 21 will be described. A valve body 1 having the axial direction of the mold opening / closing direction is incorporated in the hole 4 of the fixed-side mold plate 3. Most of the valve body 1 is constituted by a cylindrical casing 2, and one end portion of the casing 2 is a flange portion 5, and is fixed and supported between the manifold 16 and the stationary side template 3. ing. At the same time, the flange portion 5 is fitted in a step portion 23 formed at the end portion on the manifold 16 side in the hole portion 4. Further, a fixing ring 7 is fitted and fixed to the outer peripheral surface of the end portion on the gate 6 side in the casing 2, and this fixing ring 7 is a cylindrical fitting surface formed in the hole 4. 24 is fitted. Thereby, the gate 6 side portion of the casing 2 is supported by the fixed-side template 3. As described above, the valve main body 1 is in contact with the fixed-side template 3 at both ends, but is a fixing member between the outer surface of the valve main body 1 and the inner surface of the hole 4 in other portions. First and second gaps 25 and 26 that are blocked by the fixing ring 7 are formed. The first and second gaps 25 and 26 are connected to the gate 6 by the fixing ring 7 so that the first gap 25 located on the gate 6 side of the fixing ring 7 is in communication with the resin as a molding material. In the second gap 26, the inflow of the resin is blocked by the fixing ring 7 and becomes an air insulation layer.
[0015]
Further, the inside of the casing 2 is a material passage 8 that allows the runner 17 in the manifold 16 to communicate with the gate 6. The material passage 8 has a substantially cylindrical shape with the mold opening / closing direction as an axial direction, but an end portion on the runner 17 side is a bent portion 31 that is bent. The bent portion 31 is formed by embedding the insert 32 in the casing 2. In addition, three or more support blades 33 extending in the mold opening / closing direction are formed on the inner peripheral surface of the distal end portion of the material passage 8 on the gate 6 side.
[0016]
Further, a linear heater 40 as 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 covered from the outer peripheral side by a cylindrical heater cover 10 made of metal. ing. Further, as shown in FIG. 3, the linear heater 40 has a non-heat generating portion 41b at the base end portion of the heat generating portion 41a. The heating portion 41a is fitted on the outer peripheral surface of the casing 2 by winding those folded into two superimposed cylindrical coil shape. Note that the linear heater 40 is tightly wound at both ends of the heat generating portion 41a, but the linear heater 40 is roughened by interposing a pair of aluminum coil-shaped spacers 43 at the central portion. This is to prevent the temperature at the center from becoming excessively higher than the temperature at the periphery. Further, the linear heater 40 coaxially incorporates a heating wire made of nichrome wire (not shown) inside the outer tube 44 made of stainless steel, and becomes an insulating material between the heating wire and the outer tube 44, for example. It has a structure in which powdered magnesia (not shown) is interposed. Further, the tip folding portion 42a of the heat generating portion 41a forms a connecting portion 45 that extends linearly so as to extend from the tip of the casing 2 to the tip of the valve body 1, and the tip side of the connecting portion 45 is horizontally oriented. Is bent. Here, since the tip folded portion 42a bent in the horizontal direction has two heat generating portions 41a folded in an overlapping manner, the tip folded portion 42a is formed in an arc shape so as to fit the tip outer peripheral surface 1a of the valve body 1. An arcuate bent portion 46 that opens and heats the outer peripheral surface 1a of the tip of the valve body 1 is formed. A step groove 47 that fits with the arc-shaped bent portion 46 is formed on the outer peripheral surface 1a of the valve body 1 to which the arc-shaped bent portion 46 is mounted, and the connecting portion 45 is connected to the step groove 47 to communicate with the connecting portion 45. A groove portion 48 is formed inside the fixed ring 7. Further, a cover portion 7A is formed on the bottom of the fixing ring 7 so as to cover the leading 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.
[0017]
The casing 2 incorporates a valve pin 36 as a valve body that moves in the mold opening and closing direction by driving of a driving device such as a hydraulic cylinder device (not shown) provided on the fixed mounting plate. The valve pin 36 is configured such that a gate closing portion 37 formed at a distal end portion on the gate 6 side is detachably fitted to the gate 6 to close the gate 6. Further, the valve pin 36 has the mold opening / closing direction as an axial direction, and an outer peripheral surface is slidably in contact with an inner edge of the support blade 33 of the casing 2 at all times. Thereby, the front-end | tip part by the side of the gate 6 of the valve pin 36 is supported. Further, the valve pin 36 is supported by a guide bush 38 fixed in the insert 32 at the end of the valve body 1 on the manifold 16 side. That is, the valve pin 36 is slidably penetrated through the guide bush 38. In order to connect the valve pin 36 to the driving device provided on the fixed side mounting plate, the valve pin 36 also penetrates the through hole 39 formed in the manifold 16.
[0018]
Reference numeral 50 denotes a movable side mold plate of the movable mold 12, and this movable side mold plate 50 forms a product cavity 13 together with the fixed side mold plate 3.
[0019]
Although not shown, the stationary mold plate 3 and the movable mold plate 50 are formed with fluid passages through which a cooling fluid such as water for cooling the product cavity 13 passes.
[0020]
Next, the operation of the above configuration will be described. First, the fixed mold 11 and the movable mold 12 are closed, and a product cavity 13 is formed between the fixed mold 11 and the movable mold 12, and then the valve pin 36 is moved away from the movable mold 12 as shown by a chain line in FIG. The gate 6 is opened by moving in the direction. 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 flows through the runner 17 of the manifold 16 and the like, and further flows into the product cavity 13 from the gate 6 through the material passage 8 in the valve body 1 and the support blades 33 in which the valve pins 36 are fitted. After the resin is filled in the product cavity 13 in this way, after holding pressure, the valve pin 36 moves toward the movable mold 12 as shown by the solid line in FIG. Close the gate 6. The resin in the product cavity 13 is actively cooled by passing a cooling fluid 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. Thereafter, the mold is closed again and the above molding cycle is repeated. Through the entire molding cycle, the resin in the material passage 8 of the valve body 1 is the outer periphery of the valve body 1 in the same manner as the resin in the runner 17 of the manifold 16. The linear heater 40 wound around the portion and the arc-shaped bent portion 46 formed at the tip folded portion 42a of the linear heater 40 wound around the tip outer peripheral surface 1a of the valve body 1 are always kept in a molten state.
[0021]
As described above, the valve body 1 originally tends to have a higher temperature at the axial center than at both ends, but in the present embodiment, the valve body 1 has a linear heater at its outer periphery. The valve body 1 is heated from an axially intermediate portion of the valve body 1 by heating the outer peripheral surface 1a of the valve body 1 with an arc-shaped bent portion 46 formed at the tip folded portion 42a of the linear heater 40. 1 is heated almost uniformly over the axial tip. Thereby, the temperature difference of the resin in the material passage 8 of the valve body 1 is reduced. Therefore, in order to ensure the fluidity of the resin in the material passage 38, it is possible to prevent a portion where the temperature of the resin is excessively high in the material passage 8, and to prevent the resin from being burned. It can prevent that the characteristic of this resin falls.
[0022]
Here, the result of measuring the temperature in the material passage 8 will be described with reference to the graph of FIG. Although already described, the horizontal axis in the graph is the distance from the tip of the valve body 1 on the gate 6 side, and the vertical axis is the temperature. The temperature was measured for each point indicated by a black circle in the material passage 8. 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. The solid line graphs b1 and b2 show the results when the set temperature is set to 250 ° C. As a result, dotted graphs c1 and c2 show the results when the set temperature is set to 200 ° C. The thin line graphs a1, b1, and c1 are the results of the conventional mold apparatus without the arc-shaped bent portion 46 that heats the tip of the valve body 1, and the thick line graphs a2, b2, and c2 are It is a result of the mold apparatus of the present Example provided with the arc-shaped bending part 46 which heats the front-end | tip part of the valve | bulb main body 1. FIG. The mold cooling temperature was set to 10 ° C.
[0023]
Comparing the case where there is no arcuate bend 46 (graphs a1, b1, c1) and the case where the arcuate bend 46 is present (graphs a2, b2, c2) In the case where the curved portion 46 is present, it is clear that the temperature difference between the axially intermediate portion and the distal end side of the valve body 1 is smaller, and the temperature distribution of the material passage 8 is more uniform.
[0024]
Further, since the linear heater 40 is wound around the outer peripheral surface of the valve body 1 in a coil shape by folding the electric heating portion 41a in a double fold, the watt density of the entire linear heater 40 can be increased, and its unit length can be increased. The calorific value of can be increased. As a result, the entire linear heater 40 can be made thin, which is advantageous in incorporating the linear heater 40 in a limited space in the mold. Furthermore, since the front end turning portion 42a of the linear heater 40 is expanded in an arc shape to heat the outer peripheral surface 1a of the valve body 1, the casing 2 of the valve body 1 is covered by one continuous linear heater 40. To the tip outer peripheral surface 1a of the valve body 1 can be heated uniformly. For this reason, 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. Further, since the outer tube 44 that covers the linear heater 40 is made of metal, the shape along the outer peripheral surface of the valve body 1 can be maintained when wound in a cylindrical coil shape, and the valve body 1 can be assembled to the valve body 1. The assembly work of the linear heater 40 to 1 is also easy. Furthermore, by forming the cover portion 7A that covers the tip folded portion 42a of the linear heater 40 on the fixing ring 7, the linear heater 40 and the molten thermoplastic resin do not come into contact with each other. Therefore, the thermal influence of the linear heater 40 due to the molten thermoplastic resin can be suppressed, and deterioration of the linear heater 40 due to heat can be prevented.
[0025]
In addition, this invention is not limited to the said Example, A various deformation | transformation implementation is possible. For example, the basic structure of the valve gate mold apparatus, the number of turns of the linear heater 40 assembled to the valve body, etc. are not limited to the above-described embodiment, and may be selected as appropriate.
[0026]
【The invention's effect】
According to the valve gate mold apparatus of the first aspect of the present invention, the linear heater can be heated almost uniformly from the axial center of the valve body to the axial tip of the valve body. The temperature difference of the resin in the passage can be reduced. Therefore, it is possible to prevent a portion in which the temperature of the resin is excessively high in this material passage from occurring, to prevent the resin from being burnt, and to prevent deterioration of the properties of the resin. It can prevent that the characteristic of a material falls . In addition, the amount of heat generated per unit length of the entire heater is increased, the entire linear heater can be made thinner, and the linear heater can be incorporated in a limited space in the mold . Furthermore, the linear heater can be reliably contacted from the axial center of the valve body to the axial tip of the valve body to heat the valve body efficiently, and the assembly work of the linear heater to the valve body is also possible. It becomes easy.
[0027]
According to the valve gate mold apparatus of the invention of claim 2, in addition to the effect of claim 1, the first gap is a heat insulating layer that communicates with the gate and into which the molding material flows.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view showing a first embodiment of a valve gate mold apparatus according to the present invention.
FIG. 2 is an enlarged sectional view of the gate part.
FIG. 3 is a perspective view of the linear heater.
4A and 4B show temperature measurement results, where FIG. 4A is a longitudinal 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
7 Fixing ring
7A Cover 8 Material passage
11 Fixed type
12 Movable type
13 Product cavity
17 Runner (material passage)
21 Valve device
24 mating surface
25, 26 First and second gaps
40 linear heater
42a Tip turning part
46 Arc bend

Claims (2)

A plurality of mold bodies that open and close each other and form a product cavity between the mold cavities, and a valve device that opens and closes a gate that communicates a material passage provided in the mold body with the product cavity. has the type unit body section valve body incorporated and held in the formed hole to the of, to form a material passage molding material communicating with the gate to the valve body, the outer periphery of the valve body In a valve gate mold apparatus provided with a linear heater wound in a coil shape on the part, the linear heater covered from the outer peripheral side by a heater cover made of metal is folded back into two, The folded linear heater is formed in a cylindrical coil shape along the outer periphery of the valve body, and the two folded linear heaters are arranged in front of the front end. To form a connecting portion extending in the axial direction leading end portion of the valve body, forming an arcuate bent portion of the leading end folded portion is opened in an arc shape so as to extend along the front end outer peripheral surface of the valve body of the linear heater A valve gate type mold device characterized by that. A fixing ring is fitted and fixed to the outer peripheral surface of the gate side tip of the valve body, and the fixing ring is fitted to a cylindrical fitting surface formed in the hole, A cover portion is formed to cover the arc-shaped bent portion, and a first gap and a second gap blocked by the fixing ring are formed between an outer surface of the valve body and an inner surface of the hole portion. The valve gate mold apparatus according to claim 1, wherein the gap is a heat insulating layer that communicates with the gate and into which the molding material flows, and the second gap is an air heat insulating layer.

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