JPH09155931A - Mold for sandwich molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make the pressure gradients in the lengthwise and lateral directions of the cavity uniform by injection charging a core material continuously to a skin material in the mold cavity from an injection unit through a spool, a cold runner provided by the cavity width and a gate. SOLUTION: The skin material melted resin injected from a first injection unit 2A becomes constant in the flowing pressure loss in the lateral direction of a mold cavity 21 from the time point of introducing into a cold runner 27 through a sprue 14 until it is injection charged in the cavity 21. Then, a core material melted resin is injection charged from a second injection unit 2B in the cavity 21 through a first resin passage 45. When the molds 7, 9 bodies are cooled, the core material melted resin is also lowered at its temperature to prevent it from being fluidized, and diffused in the skin material semi-melted and solidified in the approximate parallel flow state. The melted resin introduced into the cavity becomes constant flowing pressure loss so that the thicknesses of the skin and core materials become uniform.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sandwich molding die for molding a sandwich molded product composed of a skin material resin and a core material resin.

[0002]

2. Description of the Related Art A molding die for molding a two-layer molded product such as a sandwich molded product or a hollow molded product has been conventionally used, for example, as shown in FIG.
Further, as shown in FIG. 9, a cavity 91 is provided, and a film gate 92 is provided in communication with the end of the cavity 91. The film gate 92 is connected to a synthetic resin device (not shown) via a runner 93 and a spool 94.

At the time of molding a sandwich molded product, first, a softened synthetic resin 81 is injected from the film gate 92 into the cavity 91 to form a surface layer. Next, the skin material synthetic resin 81 softened from the film gate 92.
Synthetic resin 82 for core material in a softened state as an injection material
Is injected to form an inner layer (FIG. 12).

[0004]

In the molding die for molding the above-mentioned conventional two-layer molded product, defective injection of the injected material occurs near the gate at the time of molding. That is, the flow of the injectate is greatly affected by the molten state of the surface layer and the pressure gradient. Then, a fairly steep pressure gradient exists in the injection direction of the injectate, and a gentle pressure gradient exists in the direction orthogonal to this. That is, there is a fairly steep pressure gradient in the longitudinal direction of the cavity 91, and a gentle pressure gradient exists in the width direction of the cavity 91. Therefore, the synthetic resin 82 as an injectate can be injected only in a slender shape in the longitudinal direction of the cavity 91, and there is a problem that the thickness of the inner layer is significantly different between the vicinity of the gate and the inner portion. As a solution to such a problem, simply lengthening only the film gate 92 as shown in FIG. 13 still cannot solve the problem.

In order to solve these problems, in Japanese Patent Publication No. 07-53396, as shown in FIGS. 10 and 11, in the vicinity of the gate in the cavity,
Arrange the weir along the direction orthogonal to the injection direction of the injectate,
By forming a gap between the weir and the side wall of the cavity, it is possible to prevent the injection defect of the injection material near the gate. That is, the synthetic resin injection device injects the softened synthetic resin 81 for forming the surface layer into the cavity 91 through the spool 94, the runner 93, and the film gate 92. Next, the synthetic resin 82 for molding the inner layer is injected into the synthetic resin 81 in the cavity 91. In this case, the synthetic resin 8 injected from the film gate 92
2 is blocked by the weir 1 and flows in the width direction of the cavity 91 along the weir 1.

A part of the synthetic resin 82 passes through the gap 2 formed on the side of the weir 1, and the synthetic resin 81 in the cavity 91.
Flows into. The other portion flows into the synthetic resin 81 through the gap 3 formed above the weir 1. The pressure gradient in the longitudinal direction of the cavity 91 of the synthetic resin 82 and the pressure gradient in the width direction of the cavity 91 are made uniform, and the synthetic resin 82 is uniformly injected into the synthetic resin 81. However, such a method causes a new problem that the structure becomes complicated.

An object of the present invention is to solve the above-mentioned problems, and to provide a sandwich molding die having a simple structure while making the pressure gradient in the longitudinal direction and the width direction of the cavity uniform. is there.

[0008]

In order to achieve the above object, in the first aspect of the present invention, an injection unit for co-injecting two or more kinds of resins is provided with a spool section, a cold runner section, and a gate section. A mold for sandwich molding, in which a skin material of a new resin is successively injected and filled into a mold cavity, and a core material of an old resin is sequentially injected to mold a sandwich molded product. The cold runner portion is a mold cavity. In the second invention having the first invention as a main component, the cold runner portion is formed in the coat hanger shape. Further, in the third invention mainly based on the first invention, the wall thickness of the resin filled in the sub-runner portion connecting the cold runner portion and the gate portion is gradually reduced in the injection direction, and in the width direction, the central portion is formed. In the fourth invention mainly based on the first invention, the gate portion is provided at the front end portion on the cold runner portion side. The cross section of the resin passage of the gate portion is minimized in the vicinity of the central portion and is gradually increased in both width directions of the mold cavity while being provided by the width of the mold cavity.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, a cold runner portion having a coat hanger shape, and a gate portion having a narrow resin passage cross section at the cold runner portion and the front end portion of the mold cavity on the cold runner portion side, respectively. The cross section of the resin passage of the gate part is gradually increased in the width direction of the mold cavity, and the sub-runner part connecting the cold runner part and the gate part is injection-filled. Since the gradient is made so as to gradually reduce the resin thickness so that it becomes thinner in the injection direction, the pressure gradient becomes uniform, so the core material resin flowing through the weir has a shape closer to the mold cavity width. Due to the so-called parallel flow that spreads evenly, the core material is injected and filled sufficiently between the skin materials, and the sand layer with a uniform thickness is used for both the inner and outer layers. Chi molded products can be obtained.

[0010]

EXAMPLES Specific examples of the shut-off nozzle of the injection molding machine according to the present invention will be described in detail below with reference to FIGS.

FIG. 1 is a plan view of a sandwich molding die,
2 is a cross-sectional view of each cross section of the sandwich molding die shown in FIG. 1, FIG. 3 is a cross-sectional view taken along line AA of FIG. 1, FIG. 4 is an explanatory view showing a filling state of the core material, and FIG. 5 is a die. FIG. 6 is an explanatory view showing the flow state of the skin material resin in the cavity, FIG. 6 is a plan view of the sandwich molding machine, and FIG. 7 is a cross-sectional view seen from BB of FIG.

Reference numeral 5 is a fixed plate of a mold clamping device (not shown) provided on the left side (referred to as the front) of the injection device 1 in the figure. The fixed board 5 has an opening 6 of a predetermined size, and a sandwich molding block 10 interposed between a fixed mold 7 and the injection unit 2 is fixedly mounted on a support 8 in the opening 6. ing. Reference numeral 41 is a movable plate, and 9 is a movable mold.

The injection unit 2 is composed of two first injection units 2A and 2B,
As shown in FIG. 1, the injection units 2A and 2B are installed so as to have an eight-character shape.
A and 2B are placed on the first base 39. Also,
Two sets of linear guides 38A, 38 are provided on the first base 39.
B is laid and these linear guides 38A, 38B
The injection unit 2 fixed on the moving bases 11A and 11B above
A and 2B can be moved back and forth together with the movable bases 11A and 11B. The forward and backward movements of the injection units 2A and 2B are rotatably supported by pin support shafts between the support base 8 and the movable bases 11A and 11B, which are erected forwardly at the tip of the first base 39. This is performed by expanding and contracting the piston rod 44a of the two hydraulic cylinder 44. Reference numeral 42 indicates a machine base on which the first base 39 is placed.

A sandwich molding block 10 is fixedly mounted on the support base 8 at the tip of the first base 39. A pair of linear guides 43 is arranged on the machine base 42, and a first base 39 on which the injection units 2A and 2B are mounted is provided on the linear guide 43 so as to be movable back and forth. The back and forth movement of the first base 39 is
One end is on the end surface of the fixed plate 5 on the injection device 1 side, and the other end is the first end.
This is performed by expanding and contracting the piston rod 40a of the first hydraulic cylinder 40 that is rotatably supported by the pin support shaft between the lower convex portions 39a of the base 39.

The inside of the sandwich molding block 10 is the second
The first resin passage 45 connected to the injection unit 2B and the first
A second resin passage 46 connected to the injection unit 2A is provided, and the inside of the block nozzle 15 disposed on the fixed plate 5 side of the sandwich molding block 10 is located with the first resin passage 45 at the center. Second resin passage 46
Is located at the outer peripheral portion, and the inner and outer annular passages are concentrically arranged by the first resin passage 45 and the second resin passage 46. The sandwich molding block 10 is heated by an appropriate heating means (not shown).

Therefore, when the piston rod 40a of the first hydraulic cylinder 40 and the piston rod 44a of the second hydraulic cylinder 44 are respectively retracted, the spool portion 14 of the fixed mold 7 and the block nozzle 15 of the sandwich molding block 10 come into contact with each other. And the contact portions 13 (13A, 13B) of the sandwich molding block 10 and the injection units 2A, 2
The injection nozzles 12A and 12B of B are connected to each other and have a closed shape. On the contrary, when the piston rod 40a of the first hydraulic cylinder 40 and the piston rod 44a of the second hydraulic cylinder 44 are respectively extended, as shown in FIG. 1, the spool portion 14 of the fixed mold 7 and the block of the sandwich molding block 10 are blocked. The nozzle 15 is separated, the abutting portion 13 (13A, 13B) of the sandwich molding block 10 and the injection nozzles 12A, 12B of the injection units 2A, 2B are separated from each other, and an open state is exhibited.

Of the inner and outer annular resin passages provided in the block nozzle 15, the second resin passage 46 located on the outer side and the first resin passage 45 located on the inner side are both at the tip end port 26 of the block nozzle 15. It merges and continues to the cold runner section 27. Further, shut-off valves 23A and 23B for opening or closing the first resin passage 45 and the second resin passage 46, respectively, are provided, and are operated by a connecting member (not shown) from the upper surface of the sandwich molding block 10. It is designed to open and close. Reference numeral 21 indicates a cavity portion.

Here, the sandwich molding die 3 of the present invention comprises a fixed die 7 and a movable die 9, and as shown in FIG. 1, the spool portion 14, the cold runner portion 27, the sub-runner portion 28, and the gate portion 29. And a mold cavity portion 21.

The molten resin injected from the injection unit 2 is introduced through the spool portion 14 into the coat hanger-shaped cold runner portion 27 having a plane of eight shapes and provided by the width of the mold cavity portion 21. It has become. On the other hand, the gate portion 29 located at the molten resin inflow port at the front end of the mold cavity portion 21 has the smallest cross section of the resin passage near the central portion as shown in FIG.
The cross section of the resin passage gradually increases in the width direction of No. 1. Therefore, as shown in FIG. 1, the distance between the cold runner portion 27 and the gate portion 29 is the longest between the cold runner portion 27 having the spool portion 14 and the gate portion 29, and gradually increases toward both ends of the mold cavity portion 21. It is configured to be short.

The cold runner portion 27 and the gate portion 29 are connected by a sub-runner portion 28, and the thickness of the resin filled in the sub-runner portion 28 is gradually reduced in the injection direction (longitudinal direction) and the width is reduced. In the direction, it has the smallest structure in the vicinity of the central portion, and gradually increases in both width directions of the mold cavity, resulting in a simple structure as a whole. That is, the slope G of the upper surface of the sub-runner portion 28 is configured to increase from the axial center position of the spool portion 14 in the width direction, and the position indicated by XX in FIG. 1, that is, the cold runner portion 27 to the gate. The slope G1 of the upper surface between the portions 29 is the gentlest, and then Y in FIG.
The gradient G2 at the position indicated by -Y, that is, the upper surface between the cold runner portion 27 and the gate portion 29 gradually increases to G1. Further, the position shown by ZZ in FIG. 1, that is, the slope G3 of the upper surface between the cold runner portion 27 and the gate portion 29 is configured to be steep following G2.

The operation of sandwich molding using the injection molding machine 1 configured as described above will be described.

Clamping subsequent to the mold closing of the fixed mold 7 and the movable mold 9 is performed by an appropriate mold clamping device (not shown) (for example, a direct pressure type or toggle type mold clamping means is used).
Next, the piston rod 40a of the first hydraulic cylinder 40 is retracted to move the first base 39 to the fixed mold 7 side, and the block nozzle 15 of the sandwich molding block 10 is moved.
Is brought into contact with the spool portion 14 of the fixed mold 7.

Further, the piston rod 44a of the second hydraulic cylinder 44 is retracted to cause the first injection units 2A, 2B to retract.
The movable pedestals 11A and 11B on which the respective parts are mounted are brought into contact with the contact portions 13A and 13B of the sandwich molding block 10 to fix the fixed mold 7, the sandwich molding block 10, the first injection unit 2A and the second injection unit 2B. To connect. Next, with the shut-off valve 23A opened (at this time, the shut-off valve 23B is closed), the screw of the first injection unit 2A is advanced into the mold cavity portion 21 formed between the molds 7 and 9. Then, the molten resin for the skin material is injected and filled through the second resin passage 46.

Then, the so-called outer layer is formed by injection filling the molten resin for the skin material into the mold cavity portion 21. When molding a molded product having an outer layer and an inner layer by sandwich molding, a virgin material is used as the skin material resin, and the core material resin forming the so-called inner layer, which will be described later, is a recycled material or a different material or a different material. A resin material is used.

First, the injection and filling of the molten resin for the skin material from the first injection unit 2A into the mold cavity portion 21 is performed as follows. The injected molten resin is injected from the tip portion 26 of the block nozzle 15 provided in the sandwich molding block 10, the spool portion 14, the coat hanger-like cold runner portion 27, the sub-runner portion 28, and the gate portion 29 into a mold. The cavity 21 is filled.

In this case, the fluid pressure loss (hereinafter referred to as fluid pressure loss) of the skin material molten resin injected and filled in the die cavity portion 21 through the gate portion 29 becomes constant in the width direction of the die cavity portion 21. It is important that the tips of the molten resin flow in parallel as shown in FIG. 5, and the skin material is evenly filled in the mold cavity portion 21. Therefore, the skin material molten resin (skin material molten resin flowing near the XX line in FIG. 1) flowing from the spool portion 14 into the cold runner portion 27 is sub-runner portion 2.
When passing through 8, since the gradient G1 of the sub-runner portion 28 that gradually decreases in the injection direction is small, the flow pressure loss is also small, and the sub-runner portion 28 circulates through the gate portion 28 having the smallest cross section of the resin passage that continues because the flow pressure loss is small. At this time, the flow pressure loss becomes large, and the mold cavity portion 21 is filled with a large flow pressure loss due to the sudden expansion as soon as it flows into the mold cavity portion 21 from the gate portion 28 having the smallest cross section of the resin passage. It is like this.

When the skin material molten resin flowing from the spool portion 14 into the cold runner portion 27 passes through the sub runner portion 28 near the Y-Y line in FIG. 1, the gradient G2 of the sub runner portion 28 which gradually decreases in the injection direction is G1. Since it is larger, the flow pressure loss is slightly increased, and the flow pressure loss generated in the sub-runner portion 28 is large. Therefore, the flow path flows through the gate portion 28 where the cross section of the resin passage in the vicinity of the Y-Y position continues to be large, and the flow pressure loss is slightly increased. The mold cavity portion 21 is filled with a large flow pressure loss due to a sudden expansion as soon as it is made to flow into the mold cavity portion 21 from the gate portion 28 which becomes smaller and has a slightly larger cross section of the resin passage.

Furthermore, when the skin material molten resin flowing from the spool portion 14 into the cold runner portion 27 passes through the sub runner portion 28 near the ZZ line in FIG. 1, the gradient G3 of the sub runner portion 28 which gradually decreases in the injection direction is G2. Since the flow pressure loss is a little larger than the above, the flow pressure loss generated in the sub-runner portion 28 is large, and the resin flow passage in the vicinity of the ZZ position continues to flow through the enlarged gate portion 28, and the flow pressure loss is increased. The mold cavity portion 21 is filled with a large flow pressure loss due to a sudden expansion as soon as it flows into the mold cavity portion 21 from the gate portion 28 which is slightly smaller and has a slightly larger cross section of the resin passage. .

As described above, the first injection unit 2A
The skin material molten resin injected from the mold cavity portion 2 passes through the spool portion 14 and flows into the cold runner portion 27 until the die cavity portion 21 is injected and filled.
The flow pressure loss can be constant in the width direction of 1.

After the injection and filling of the molten resin for the skin material is completed, the holding pressure is continued while the forward limit position of the screw is maintained. After this, the shutoff valve 23A
Is closed, and in preparation for the next cycle, the screw of the first injection unit 2A is rotated and retracted to perform measurement.

Next, after a predetermined amount of the molten resin for the skin material is injected and filled into the mold cavity portion 21, the shut-off valve 2
3B open (at this time, shutoff valve 23
(A is closed), the screw is moved forward in the second injection unit 2B, and an appropriate amount of core material molten resin is injected into the mold cavity portion 21 through the first resin passage 45. In this embodiment, the mold 7 is used. , 9 Cool the body uniformly.

When the main bodies of the molds 7 and 9 are cooled, the temperature of the core material molten resin injected and filled in the mold cavity portion 21 is also lowered, the flow is prevented and the inside of the skin material molten resin flows. Although the flow of the core material molten resin becomes an approximately parallel flow, since the flow pressure loss of the molten resin until it flows into the mold cavity portion 21 is constant, the core material melted in the skin material molten resin as a whole is melted. The resin diffuses in the semi-melted and solidified skin material in the state of an approximate parallel flow.

After this, the shut-off valve 23A is again used.
The mold cavity portion 2 formed between the molds 7 and 9 in a state in which the mold is opened (at this time, the shutoff valve 23B is closed).
By advancing the screw of the first injection unit 2A into 1 and injecting and filling the skin material molten resin through the second resin passage, the core material resin is sealed with the skin material resin, and the sandwich molded product is obtained. It is molded. In addition,
First injection unit 2 after injection filling of skin material molten resin is completed
The screw on the A side is advanced to apply a holding pressure to the molten resin in the mold cavity portion 21.

After the pressure holding is completed, both the first injection unit 2A and the second injection unit 2B perform the measurement in the next cycle with the shut-off valve 23A closed (the shut-off valve 23B is already kept closed). Both molds 7, 9
After cooling for a predetermined time, both molds 7 and 9 are opened to take out the product.

[0035]

As is apparent from the above description, in the present invention, the molten resin flowing into the mold cavity through the coat hanger-shaped cold runner portion, sub-runner portion, and gate portion has a constant flow pressure loss. Therefore, the length from the cold runner part to the mold cavity part can be shortened, and the core material resin is uniformly injected between the skin material resin, so that the skin material and the core material have a uniform wall thickness. A simple sandwich molded product can be easily obtained.

[Brief description of the drawings]

FIG. 1 is a plan view of a sandwich molding die of the present invention.

FIG. 2 is a cross-sectional view of each cross section of the sandwich molding die shown in FIG.

3 is a sectional view taken along line AA of FIG.

FIG. 4 is an explanatory diagram showing a filled state of a core material.

FIG. 5 is an explanatory view showing a flow state of a skin material resin in a mold cavity.

FIG. 6 is a plan view of the sandwich molding machine.

7 is a cross-sectional view as seen from BB of FIG.

FIG. 8 is a plan sectional view of a molding die in a conventional molding state.

FIG. 9 is a side sectional view of FIG. 8;

FIG. 10 is a plan sectional view of a molding die in a conventional molding state.

FIG. 11 is a side sectional view of FIG. 10;

FIG. 12 is an explanatory view showing a state of injection and filling into a mold having a shape of a conventional spool portion and a cold runner portion.

FIG. 13 is an explanatory view showing a state of injection filling into the mold when the cold runner portion is made longer than that in FIG. 12;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Injection device 2 Injection unit 2A 1st injection unit 2B 2nd injection unit 3 Sandwich molding die 5 Fixed plate 6 Opening 7 Fixed die 9 Movable die 10 Sandwich molding block 11A, 11B Moving stand 12 (12A, 12B) Injection nozzle 13 (13A, 13B) Contact part 15 Block nozzle 21 Mold cavity part 23A, 23B Shut-off valve 26 Tip opening 27 Cold runner part 28 Sub-runner part 29 Gate part 38A, 38B, 43 Linear guide 39th 1 Base 40 1st hydraulic cylinder 41 Movable plate 44 2nd hydraulic cylinder 45 1st resin passage 46 2nd resin passage

Claims (4)

[Claims] 1. A new resin skin material is successively injected into a mold cavity through an injection unit for co-injecting two or more kinds of resins through a spool portion, a cold runner portion, and a gate portion, and then an old resin core material is filled. A mold for sandwich molding for injection-molding a sandwich molded article, wherein the cold runner portion is provided by the width of the mold cavity. 2. A sandwich molding die, wherein the cold runner portion according to claim 1 is formed into a coat hanger shape. 3. The thickness of the resin filled in the sub-runner portion connecting the cold runner portion and the gate portion according to claim 1 is gradually reduced in the injection direction and is made the smallest in the width direction near the central portion. And a mold for sandwich molding, wherein the mold is gradually increased in both width directions of the mold cavity. 4. The gate portion according to claim 1 is provided at the front end portion on the cold runner portion side by the width of the mold cavity, and the resin passage cross section of the gate portion is minimized in the vicinity of the central portion, and the mold is also formed. A sandwich molding die characterized in that it gradually increases in both width directions of a cavity.