JPH06285911A - Resin forming mold and weld line reinforcing method - Google Patents

Abstract

PURPOSE:To provide a weld line reinforcing method wherein sufficient strength can be obtained, the cost is advantageous, process is not so complicated, and to provide a mold for carrying out the method. CONSTITUTION:A small space 22 for lowering a pressure of either a resin flow 18 or a resin flow 20 which is injected from one or two gates 12, 14 becoming a confluence in a cavity 16 is provided so as to communicate with the cavity 16 at a position nearer to the gate 12 than a position where a weld line is to be formed. After a full shot, a valve 22B at an inlet of the small space is artificially opened or automatically opened in response to the resin pressure. By opening and closing the gates, one resin pressure of the resin flow is lowered and other resin pressure is raised relatively, thereby forming a weld line having deep irregularity for improving the strength and appearance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention, when a synthetic resin is injected into a mold to be molded, two or more flows of the injected resin meet in a resin filling space inside the mold to form a weld line. In this case, the present invention relates to a resin molding die and a weld line reinforcing method for increasing the strength of the weld line.

[0002]

2. Description of the Related Art In a mold for injection molding, depending on the shape of a molded product such as an object with holes or a louver of an air conditioner,
In some cases, the resin flow cannot but be divided in the resin filling space (cavity) inside the mold. Two or more flows that have been split are joined together, and the joined portions are solidified without being sufficiently fused with each other, and a weld line (also called a weld portion)
To form. A problem with the weld line formed at this joining portion is that its strength is lower than that of the other portions. In particular, in the case of a resin or polymer alloy reinforced by glass fiber (GF) or carbon fiber (CF), the tensile strength of the weld line of the molded product is caused by the reason that the orientation direction of the fiber is likely to be along the weld line at the joining portion. , Bending strength and impact strength are apt to decrease.

As a method for solving this problem, the resin temperature, the injection pressure, and the mold temperature, which are various conditions at the time of molding, are increased and the injection speed is increased, and further, the mold design. In, the gate size is increased, the thickness of the molded product is increased, and sufficient degassing is achieved.
More recently, MLFM (Multi Live Feed Molding) or shear orientation control injection described on page 4 and below of "Interplus 90 Inspection and Precision Injection Mold / Molding Technology Study Team Report" issued by Plastic Industry Research Group. The method of using two pistons, which is known as the control of fibers in composite material molding by molding, and the twin screw injection molding method shown on page 217 and below of "Molding processing '92" issued by Japan Society for Plastic Molding Processing have been developed. There is.

Further, as shown in JP-A-63-221023 and JP-A-2-202414, a part of the tip of one molten resin enters the tip of the other molten resin at the confluence. There is a method of forming a recess.
Furthermore, as shown in JP-A-4-310715 and "Plastic Age", "Development of Weld Countermeasure Injection Molding Technology", March 1993, pp. 175-179.
There is a method of using a resin retainer for providing a pressure difference to the resin flow that has flowed into the cavity.

[0005]

In the above-mentioned conventional techniques, in the method of adjusting various conditions at the time of molding or changing the design condition of the mold, it is necessary to repeat trial and error until the optimum condition is found, and it is not always necessary. In some cases, sufficient strength may not be obtained. In addition, the MLFM and twin screw injection molding methods that use two pistons make the molding machine larger and more complicated,
There is a problem of increasing costs. Further, in the weld line reinforcing method described in JP-A-63-221023, it is necessary to dispose a bent plate or a pin in the cavity in advance in order to form a recess at the tip of one flow, which complicates the process and is practical. There was a problem not. Further, in the method described in JP-A-2-202414, the opening / closing timing of the gate is simply adjusted, and it is not possible to form a sufficiently deep uneven shape. Therefore, it was not always possible to obtain sufficient strength. Further, in the method described in JP-A-4-310715 and "Plastic Age" March 1993, one of the resin streams flowing from the two gates flows into the resin reservoir.
Although a pressure difference occurs, the difference is not always sufficient,
It was not possible to form a weld line having a sufficiently deep uneven shape, and the strength was also insufficient.

Therefore, an object of the present invention is to provide a method for reinforcing a weld line which has sufficient strength, is advantageous in terms of cost, and is not so complicated in the process, and a mold therefor. .

[0007]

In order to achieve the above object, in the present invention, a small space communicating with the cavity is provided, a valve is provided at the inlet thereof, and molten resin is injected into the cavity from two gates. The gate on the side of the small space is closed and then the valve is opened to reduce the pressure of the resin in the vicinity thereof, so that the recess is formed in the weld line. Manual or sequential control can be used to open this valve. Furthermore, by detecting the resin pressure,
The valve may be opened automatically when a predetermined value is exceeded.

That is, according to the present invention, a mold body for defining a resin filling space for molding a synthetic resin molded product, and a first mold for injecting a molten resin from a first predetermined position of the resin filling space. A resin molding die having one gate and a second gate for injecting resin from a second predetermined position apart from the first predetermined position in the resin filling space, wherein the first gate and the second gate are provided. When the molten resin is simultaneously injected from the gate, the two flows of the molten resin respectively injected from the two gates meet in the resin filling space to form a weld line from the third predetermined position. A small space for retracting the molten resin injected from the first gate into the resin filling space at a point close to a first predetermined position, and an inlet on the resin filling space side of the small space. Normally, the valve is closed, and after the molten resin is injected from the first and second gates, the first gate is closed, and then the inlet is opened to introduce the molten resin into the small space and withdraw it. A resin molding die is provided which has a means.

Further, according to the present invention, a mold body for defining a resin filling space for molding a synthetic resin molded product, and a molten resin for injecting the molten resin from a first predetermined position of the resin filling space. A resin molding die having a first gate and a second gate for injecting resin from a second predetermined position apart from the first predetermined position in the resin filling space, wherein the first gate and the second gate are provided. When the molten resin is simultaneously injected from the two gates, two flows of the molten resin injected from the two gates meet in the resin filling space to form a weld line from a third predetermined position. Pressure detection means for detecting that the pressure of the injected molten resin at a point near the first predetermined position exceeds a predetermined value, and the tree at a point closer to the first predetermined position than the third predetermined position. And a small space for retracting the injected from the first gate into the filling space molten resin, the entrance of the resin charging space side of the small space keep normally closed,
A valve means for opening the inlet and guiding a part of the molten resin into the small space and withdrawing the molten resin when the pressure exceeds the predetermined value in response to the pressure detecting means. A resin molding die is provided.

Further, according to the present invention, a mold body for defining a resin filling space for molding a synthetic resin molded product, and a molten resin for injecting the molten resin from a first predetermined position of the resin filling space. In a resin molding die having a first gate and a second gate for injecting resin from a second predetermined position apart from the first predetermined position in the resin filling space, a molten resin is injected from the first gate. When molten resin is injected, the molten resin injected from the first gate splits in the resin filling space, and two or more flows meet each other, and the weld resin is sandwiched between the third predetermined positions. And a small space provided at a position facing the second gate for retracting the molten resin injected from the first gate into the resin filling space, and an inlet on the resin filling space side of the small space. Normally Flip advance, after the first gate is closed from the first gate after a molten resin is injected,
There is provided a resin molding die, comprising: a valve means for opening the second gate and opening the inlet to guide and withdraw the molten resin into the small space.

Further, according to the present invention, a mold body for defining a resin filling space for molding a synthetic resin molded product, and a molten resin for injecting the molten resin from a first predetermined position of the resin filling space. In a resin molding die having a first gate and a second gate for injecting resin from a second predetermined position apart from the first predetermined position in the resin filling space, a molten resin is injected from the first gate. When the resin is injected, the molten resin injected from the first gate splits in the resin-filled space, two or more flows meet, and a weld line is expected to form a third predetermined position. 1
The pressure detection means for detecting that the pressure of the injected molten resin at a point close to the predetermined position exceeds a predetermined value, and the pressure detection means is provided at a position facing the second gate across the third predetermined position. A small space for retracting the molten resin injected from the first gate into the resin filling space and an inlet on the resin filling space side of the small space are normally closed, and in response to the pressure detecting means. Provided is a resin molding die, comprising: a valve means for opening the inlet and guiding a part of the molten resin into the small space to withdraw when the pressure exceeds the predetermined value. It

Further, according to the present invention, a part of the first tip of the molten resin injected from the first gate in the resin filling space for molding the synthetic resin molded product is injected from the second gate. In a method for reinforcing a weld line in which a concave portion for entering the second tip of the molten resin is formed in the second tip, the weld line is connected to the resin filling space, and the weld line is expected to be formed from a predetermined position. A small space with a valve for evacuating the molten resin injected from the first gate is provided at a point close to one gate, and the first and second gates are opened to allow the inside of the resin filling space from each gate. At the same time, the molten resin is injected, and after a lapse of a predetermined time, the first gate is closed, the valve of the small space is opened, and a part of the molten resin injected from the first gate is guided into the small space. Evacuate Weld line reinforcement and wherein the door is provided.

Further, according to the present invention, a part of the first tip of the molten resin injected from the first gate located at the first predetermined position in the resin filling space for molding the synthetic resin molded product is aforesaid. The second recess is provided for entering the second tip of the molten resin injected from the second gate at the second predetermined position in the resin space.
In the method for reinforcing a weld line formed at a tip, the first and second gates are opened, a molten resin is simultaneously injected into the resin filling space from each of the gates, and the molten resin is injected from each of the two gates in the resin space. It is detected whether the pressure of the injected molten resin exceeds a predetermined value at a point closer to the first predetermined position than the third predetermined position where it is expected that the two flows of the melted molten resin meet to form a weld line. However, after a lapse of a predetermined time after opening the first and second gates and simultaneously injecting, or when the pressure exceeds the predetermined value, only the first gate is closed and the third predetermined position is exceeded. A small space for evacuating the molten resin injected from the first gate is provided at a point near the first predetermined position, and the small space is provided at the inlet on the resin filling space side. The means is normally closed, and when the pressure exceeds the predetermined value due to the detection of the pressure, the valve means is opened to guide a part of the molten resin into the small space and withdraw it. A method of reinforcing a weld line is provided.

Further, according to the present invention, the synthetic resin molded product to be molded has a through hole, and the molten resin injected from the first gate and the second gate surrounds the through hole. 9. The method for reinforcing a weld line according to claim 7, wherein the positions of the first gate and the second gate are selected so as to form a weld line by shunting each of them and joining at least two predetermined positions. To be done.

Further, according to the present invention, the molten resin injected from the first gate is shunted around the through hole in the resin filling space for molding the synthetic resin molded product having the through hole. In the weld line reinforcing method of forming a recess at the one tip so that they merge and a part of one tip enters the other tip, the weld line is formed so as to communicate with the resin filling space. A small space with a valve for evacuating the molten resin injected from the first gate is provided at a point closer to the first gate than an expected predetermined position, and the first gate is opened to open the first gate. The molten resin is injected into the resin filling space from above, and after a predetermined time has passed, the first gate is closed, and the first gate is opposed to the predetermined position where the weld line is expected to be formed. The second gate at the position is opened to further inject the molten resin into the resin filling space, and the valve of the small space is opened to partially discharge the molten resin injected from the first gate into the small space. A method for reinforcing a weld line is provided, which is characterized by guiding and retracting.

Further, according to the present invention, the molten resin injected from the first gate at the first predetermined position in the resin filling space for molding the synthetic resin molded product having the through hole has the through hole. In the weld line reinforcing method, the first gate is opened and the first gate is opened in the weld line reinforcing method, in which a concave portion is formed in the one tip by diverging into the surroundings and joining them so that a part of the one tip enters the other tip. The molten resin is injected from the gate into the resin filling space, and two or more shunts of the molten resin injected from the first gate meet in the resin space to form a weld line. It is detected whether or not the pressure of the injected molten resin at a point closer to the first predetermined position than the position exceeds a predetermined value, and the predetermined time elapses after the first gate is opened and the simultaneous injection is performed, or Exceeds the predetermined value, the first gate is closed, the second predetermined position is sandwiched, and the second gate located opposite to the first gate is opened to fill the molten resin with the molten resin in the filling space. And a small space for retracting the molten resin injected from the first gate is provided at a point closer to the first predetermined position than the third predetermined position. Normally, the valve means provided at the inlet on the filling space side is closed, and when the pressure exceeds the predetermined value by the detection of the pressure, the valve means is opened to partially melt the molten resin into the small space. A method for reinforcing a weld line is provided, which is characterized in that the weld line is guided and retracted.

Further, according to the present invention, it is injected from the first gate provided on the thick portion side in the resin filling space for molding the synthetic resin molded product having the thick portion and the thin portion. In a weld line reinforcing method in which a recess for allowing a part of one tip of a branched flow of molten resin to enter the tip of another branch is formed at one tip of the branched flow, the weld line is communicated with the thin portion of the resin-filled space. A small space with a valve for evacuating the molten resin injected from the first gate is provided at a position facing the first gate across a predetermined position where the weld line is expected to be formed. , Opening the first gate, injecting molten resin from the first gate into the resin filling space, closing the first gate after a lapse of a predetermined time, and presumably forming the weld line. Position The molten resin is injected from the second and third gates into the resin filling space by opening the second gate and the third gate provided at the position facing the entrance of the small space and on the thick portion side. At the same time, the weld line reinforcing method is provided, characterized in that the valve of the small space is opened to guide a part of the molten resin injected from the first gate into the small space to evacuate.

Further, according to the present invention, the first gate located in the resin-filled space for molding the synthetic resin molded product having the thick portion and the thin portion at the first predetermined position of the thick portion. In the weld line reinforcing method, a recess is formed at one end of the split flow so that a part of one end of the split flow of the molten resin injected from the other end enters the tip of another split flow.
The gate is opened, the molten resin is injected from the first gate into the resin filling space, and it is detected whether or not the pressure of the injected molten resin in the thin portion in the resin space exceeds a predetermined value. 1 When a predetermined time has elapsed after opening the gate and injecting, or when the pressure exceeds the predetermined value,
A second gate and a third gate which are provided in the thick portion at a position facing the entrance of the small space across the position where the weld line is expected to be formed by closing the first gate. And a molten resin injected from the second and third gates into the resin filling space, and the molten resin injected from the first gate to a point closer to the first predetermined position than the third predetermined position. Has a small space for retreating, and the valve means provided at the resin filling space side entrance of the small space is normally closed, and the pressure exceeds the predetermined value by the detection of the pressure. At the same time, there is provided a weld line reinforcing method, characterized in that the valve means is opened and a part of the molten resin is guided into the small space and retracted.

[0019]

Since the present invention has the above-mentioned structure, the opening / closing of the gate is operated, and when the valve is opened, the resin in the vicinity is guided to the small space and retracts, whereby the pressure of the flow on the opposite side in the portion where the weld line can be formed. Is relatively high,
The central portion of the tip of the flow flows in, and the uneven weld line is formed deeply. Therefore, the strength of this portion is increased.

[0020]

Embodiments of the present invention will be described below with reference to the drawings. 1 is a schematic front sectional view showing a first embodiment of a mold of the present invention, FIG. 2 is a schematic plan sectional view thereof, and FIG. 3 shows an uneven portion formed in a weld line in the mold. FIG. 4 is a schematic front cross-sectional view showing a state in which the above is performed. 1 to 3, the resin molding die is indicated by 10 in its entirety, and has a resin filling space (cavity) 16 inside. Resin filling space 1
First and second gates 12 and 14 for injecting the molten resins 18 and 20 are provided near both ends of 6.
Further, a resin reservoir 22 as a small space communicating with the resin filling space 16 is provided near the first gate 12 of the resin filling space 16. This resin reservoir 22 has a first
Guide a part of the molten resin 18 injected from the gate 12,
It is for evacuating. The resin reservoir 22 is provided with a valve 22B at an inlet 22A on the resin filling space 16 side.

Next, the operation of the first embodiment shown in FIGS. 1 to 3 will be described. First, the first gate 12 and the second gate 1
The molten resins 18 and 20 are simultaneously injected and injected from 4, respectively. That is, a so-called full shot is performed. In addition,
Here, “full shot” means that the resin injected from the two gates 12 and 14 is injected and filled until they merge. At this time, the valve 22B of the resin reservoir 22 is closed. The injected resin meets as two flows 18 and 20 near the center of the resin filling space 16 and joins them. At this time, weld line 2 between the tips of each flow
4A is being formed. After the full shot, only the first gate 12 is closed. Immediately after or at the same time, the resin reservoir 2
Open the second valve 22B. Then, as shown in FIG. 2, the pressure of the molten resin 20 flowing from the second gate 14 is changed to the first gate 1
Since it becomes higher than the pressure of the molten resin 18 flowing from 2,
A part of the molten resin 18 is introduced into the resin reservoir 22. Due to this partial withdrawal, as shown by the dotted line in FIG. 2, the central portion of the weld line 24A enters the right side in the drawing to form an uneven shape. That is, as shown also in FIG. 3, an uneven weld line 24B is formed in which the center of the tip of one resin flow enters into the tip of the other resin flow. The valve 22B is omitted in FIGS. 2 and 3. The valve 22B may be manually operated in principle, but it is desirable that the valve 22B be capable of performing sequential control by being controlled by a timer according to the operation of the gates 12 and 14.

FIG. 4 is a partial sectional view schematically showing the flow of resin in the mold. In FIG. 4, 26 indicates a solidified layer, 2
8 shows a fluidized bed. That is, it shows that the portion near the inner wall of the mold 10 is solidified because it cools quickly, and the central portion of the flow is going forward. Due to the synergistic effect of the property of the resin flow and the opening of the resin reservoir 22 as the small space, the uneven weld line 24B as shown in FIGS. 2 and 3 is formed.

Next, a second embodiment of the present invention will be described with reference to FIGS. 5 and 6 are schematic front cross-sectional views of the mold as in FIGS. 1 and 3. In this embodiment, the small space 3 communicating with the resin filling space 16 at a position where the weld line 24B is expected to be formed, that is, at a position closer to the first gate 12 than the approximate middle point of the resin filling space 16 in the figure.
6 is provided. The small space 36 acts as a hole for dropping the resin. This small space 36 has, for example, a cylindrical shape, a pin 34 that operates as a valve is provided at the inlet on the resin filling space 16 side, and the coil spring 32 that is compressed by the pressure of the resin 18 that operates on the pin 34 is the small space 36. It is provided inside. Although the pin 34 is shown only in the head portion, there is actually a rod portion that slides in the coil spring 32 under the head portion.

The operation of the second embodiment shown in FIGS. 5 and 6 will be described. As shown in FIG.
The entrance of 6 is closed, and in this state, a full shot is similarly performed from the first gate 12 and the second gate 14. After the full shot, the first gate 12 is closed. 1st gate 1
Since the resin flowing in from 2 disappears, the pressure on the right side in FIG. 6 becomes relatively high, so that the pin 34 is effectively lowered, and the uneven shape of the weld line 24B becomes deep. As shown in FIG. 6, when the two resin streams 18 and 20 are merging to form a weld line, the resin stream 18
The coil spring 32 is compressed by the increase in pressure of the pin 3
4 descends, thus opening the entrance to the small space 36. Therefore, since a part of the resin 18 flows into the small space 36, the pressure of the resin flow 20 on the right side in the drawing becomes higher than that of the resin flow 18 on the left side, and the uneven weld line 24B is formed as in the first embodiment. The pressure before the resins 18 and 20 merge is 50
~ 200 kg / cm ² , but 200 to 10 when they merge
It rises to 00 kg / cm ² .

In the second embodiment described above, the pin is lowered according to the pressure of the resin. However, the configuration is not limited to this, and the pressure of the resin is reduced at a position closer to the first gate 12 than the position where the weld line 24B is formed. It suffices if the pressure is detected and the inlet of the small space 36 is opened when the value exceeds a predetermined value, and other pressure detecting means and a solenoid valve or a mechanical valve means responsive thereto can be used. .

Next, a third embodiment of the present invention will be described with reference to FIGS. FIG. 7 shows a third embodiment, and FIG. 8 shows a variation thereof. This third embodiment and its variation are suitable when the resin product to be molded has one or more through holes. In the first and second embodiments, two gates 1 are used.
Although 2 and 14 are simultaneously opened to inject the resin into the cavity 16 from both gates 12 and 14, only the first gate 12 is first opened to inject the resin in this embodiment. as a result,
The resin flow is divided into left and right of the through hole 38,
The weld line is formed by joining at the position of the weld line indicated by A. At this time, the first gate 12 is closed, the second gate 14 is opened, and the valve 22 in the small space 22 is closed.
Open B. Then, the resin flows from the second gate 14, the pressure on the right side of the weld line 24A in the figure becomes higher than that on the left side, and a part of the resin flows into the small space 22. As a result, an uneven portion is formed on the weld line 24A from the right side to the left side in the figure. In the case of the variation of FIG. 8, since there are two holes 38A and 38B, there are three resin flows from the first gate 12, and two weld lines 24A and
Although 24B is formed, the same state is obtained by the same operation as described above.

Here, the first gate 12 and the second gate 14
Considering the position where the small space 22 is provided, first, the first gate 12 is provided at an arbitrary position so that the resin injected from the first gate 12 quickly flows into the cavity. As a result, the divided resin flows merge to determine the positions where the weld lines 24A and 24B are formed. The second gate 14 and the small space 22 are connected to the weld line 24.
It is most desirable that the weld lines 24A are provided at positions opposite to each other with the expected formation of the weld lines 24A therebetween so that irregularities can be effectively formed on A and 24B.

As for the timing of closing the first gate 12, the timing of opening the second gate 14, and the timing of opening the valve 22B, a timer or pressure detection can be used as in the above two embodiments. Table 2 schematically shows the operation of the third embodiment. Table 1 schematically shows the operation of the first and second embodiments. In these tables, ◯ indicates the open state of the gate or the valve, and x indicates the closed state.

[0029]

[Table 1]

[0030]

[Table 2]

Next, a fourth embodiment of the present invention will be described with reference to FIG. This embodiment is for making a molded product having holes as in the third embodiment. The first gate 12 and the second gate 14 are provided so as to be in contact with a hole 38C which is a central through hole, and the position of the gate is determined so that the two weld lines 24A and 24B are formed at desired positions. You can The operation of the fourth embodiment is as shown in Table 3 below.

[0032]

[Table 3]

That is, the first gate 12 and the second gate 1
4 is opened, resin is injected, weld line 24
A and 24B are formed. After that, the first gate 12 is closed and the valve 22B of the small space 22 is opened. As a result, the pressure on the left side of the figure increases, and the weld lines 24A, 24
B has an uneven shape that flows from left to right.

Next, a fifth embodiment of the present invention will be described with reference to FIG. This embodiment is suitable for a so-called uneven thickness molded product having a change in thickness. 10A shows a plan sectional view, and B shows a side sectional view. Three gates are used in this embodiment. That is, the cavity 16
A first gate 12 provided on the thick side 16A at the center of
The second gate 14 provided near both ends of the thick side 16A
A and the third gate 14B. Further, a small space 22 having a valve 22B is provided at the center of the thin portion 16B side.
The fifth embodiment operates as shown in Table 4.

[0035]

[Table 4]

As shown in Table 4, only the first gate 12 is opened and the cavity 16 is filled with resin. Since the resin has a property of flowing to the thicker side, the resin is diverted in the cavity 16 and weld lines are formed at the positions indicated by 24A and 24B. Then, the first gate 12A is closed, the second gate 14A and the third gate 14B are opened, and the valve 22B is opened.
As a result, the resin flows from the second gate 14A and the third gate 14B, and the resin in the vicinity of the small space 22 becomes small.
2, and unevenness is generated in the weld lines 24A and 24B. In order to effectively produce this unevenness, the second
It is desirable that the gate 14A and the entrance 22A of the small space 22 are opposite to each other across the weld line 24A, and similarly, the third gate 14B and the entrance 22A are in the weld line 2.
It is desirable to be in the opposite position with 4B in between.

The timing of opening and closing each gate and the timing of opening the valve 22B and the pin 34 in each of the above-mentioned embodiments vary depending on the size of the cavity, the pressure of the resin, etc. It takes about 3 seconds from the formation of the weld line to the formation of the weld line. At this time, as shown in each table, opening and closing of the gate and opening of the valve 22B and the pin 34 are performed, and a pressure holding time of 10 to 20 seconds is provided.
The valve 22B of the third to fifth embodiments is the pin 34 of FIG.
May be

[0038]

As described above, according to the present invention, the pressure of one resin flow in the resin filling space 16 is reduced, or because the resin is further injected from another gate, the other resin flow is relatively discharged. As a result, the pressure rises and the weld line formed at the confluence of the two can have a deep uneven shape. Therefore, the strength of the weld line can be sufficiently increased, and it becomes possible to provide a practical mold that can be used in an inexpensive molding machine and a method for reinforcing the weld line.

Further, in the present invention, the depth of the uneven shape of the weld line 24B can be changed by changing the volume of the small space, that is, the resin reservoir 22 of the first embodiment and the trap hole 36 of the second embodiment. Further, the small space can be provided at the outer peripheral portion of the product or near the central portion of the product, which makes it possible to design a mold that meets the needs of the product to be molded. Further, not only the strength in the weld line is improved, but in the fiber reinforced material, the orientation of the fibers is changed to that along the weld line, so that the fiber is smoothed and the appearance is improved. FIG. 11 is a perspective view schematically showing an injection-molded product molded according to the present invention. As shown by E, when a cross section of a part of the weld line 24 is enlarged and examined, As can be seen, the surface is flat. A in FIG. 12 is obtained by the conventional method, and the degree of improvement in appearance can be seen from the comparison of the undulations of A and B.

In order to evaluate products having deep irregularities in the weld line according to the present invention, in terms of strength and smoothness of appearance, one without a weld line (one-way injection molded product without joining) and a conventional product. The results shown in Table 5 were obtained by comparison between the method and the one provided with irregularities according to the present invention. The PC / ABS alloy shown in Table 1 is a PC / ABS polymer alloy manufactured by Mitsubishi Rayon Co., Ltd., which is known as DIA ALLOY (trademark) FC-30, while GF-containing ABS (20%). What is shown is the company's glass fiber 20% ABS, known as Diapet ™ ABSDG-120. As can be seen from this table, the strength of the molded product obtained according to the present invention is comparable to the molded product having no weld line depending on the type of resin.

[0041]

[Table 5]

The mold used in the above comparative test is 250 mm ×
50mm and thickness is 2mm and 3mm,
As described above, there are two gates. As the molding machine, N140BII (mold clamping force 140T) manufactured by Japan Steel Works was used. The molding conditions were set to the values shown in Table 6 for each resin used.

[0043]

[Table 6]

Further, in order to evaluate the injection-molded article obtained by the present invention, photographs were taken of the fracture surface and the cross section of the weld portion. FIG. 13 is a photograph showing the state of a fractured portion that was fractured by applying an external force in the weld line of the molded article molded according to the first embodiment shown in FIGS. 1 to 3 using the ABS resin containing 30% of glass fiber. is there. The white parts in the photo are the molded parts, and the black parts are the background. As can be seen from this figure, a large number of glass fibers are projected at the weld line portion, and it can be seen that the glass fiber is deeply entangled in the other resin flow to be reinforced.

FIG. 14 is a photograph of a cross section showing a weld line of a molded product similarly molded according to the first embodiment. It is easy to see how one resin flow digs deeply into the other. Although FIGS. 13 and 14 show the one according to the first embodiment, it has been confirmed that substantially the same effect is produced also in the case of the other embodiments.

[Brief description of drawings]

FIG. 1 is a schematic front sectional view showing a first embodiment of a mold and a weld line reinforcing method of the present invention.

FIG. 2 is a schematic plan sectional view showing a first embodiment of a mold and a weld line reinforcing method of the present invention.

FIG. 3 is a schematic front cross-sectional view showing how unevenness is formed on a weld line in the first embodiment.

FIG. 4 is a partial cross-sectional view schematically showing the flow of resin in a mold.

FIG. 5 is a schematic front sectional view showing a second embodiment of the mold and the weld line reinforcing method of the present invention.

FIG. 6 is a schematic front sectional view showing a second embodiment of the mold and the weld line reinforcing method of the present invention.

FIG. 7 is a schematic plan sectional view showing a third embodiment of the mold and the weld line reinforcing method of the present invention.

FIG. 8 is a schematic plan sectional view showing a variation of the third embodiment.

FIG. 9 is a schematic plan sectional view showing a fourth embodiment of the mold and the weld line reinforcing method of the present invention.

FIG. 10 is a schematic plan sectional view (A) and a schematic side sectional view (B) showing a fifth embodiment of the mold and the weld line reinforcing method of the present invention.

FIG. 11 is a perspective view schematically showing an injection-molded article formed by the present invention.

FIG. 12 is a diagram showing surface roughness showing an improvement in the appearance of a weld line according to the present invention in comparison with a conventional method.

FIG. 13 is a photograph showing a fracture surface of a molded article according to the present invention.

FIG. 14 is a photograph showing a welded part of a molded product according to the present invention.

[Explanation of symbols]

 10, 30 Mold 12 First gate 14 Second gate 16 Resin filling space 18, 20 Resin (flow) 22 Resin reservoir (small space) 22A Inlet 22B valve 24A, 24B Weld line 26 Solidification layer 28 Fluidized bed 32 Coil spring 34 pins 36 Pitfall (small space) E Part of the weld line on the product

Claims (14)

[Claims] 1. A mold body for defining a resin filling space for molding a synthetic resin molded product, a first gate for injecting a molten resin from a first predetermined position of the resin filling space, A second resin-filled space separated from the first predetermined position.
A resin molding die having a second gate for injecting a resin from a predetermined position of the two gates in the resin filling space when a molten resin is simultaneously injected from the first gate and the second gate. It is expected that two flows of molten resin injected from the gate will meet and form a weld line.
A small space for retracting the molten resin injected from the first gate into the resin filling space at a point closer to the first predetermined position than the predetermined position, and an inlet of the small space on the resin filling space side. Is normally closed, and after the molten resin is injected from the first and second gates and then the first gate is closed, the inlet is opened to guide the molten resin into the small space and to withdraw. A resin molding die having a valve means. 2. A mold main body which defines a resin filling space for molding a synthetic resin molded product, a first gate for injecting a molten resin from a first predetermined position of the resin filling space, A second resin-filled space separated from the first predetermined position.
A resin molding die having a second gate for injecting a resin from a predetermined position of the two gates in the resin filling space when a molten resin is simultaneously injected from the first gate and the second gate. It is expected that two flows of molten resin injected from the gate will meet and form a weld line.
Pressure detection means for detecting that the pressure of the injected molten resin at a point closer to the first predetermined position than the predetermined position, and a point closer to the first predetermined position than the third predetermined position. A small space for retracting the molten resin injected from the first gate into the resin filling space, and an inlet of the small space on the resin filling space side are normally closed to respond to the pressure detecting means. And a valve means for opening the inlet and guiding a part of the molten resin into the small space to withdraw when the pressure exceeds the predetermined value. 3. The pin, wherein the valve means is slidably arranged in the small space and has a head for closing an inlet of the small space, and the pressure detecting means is responsive to the pin and the pressure. The resin molding die according to claim 2, further comprising a coil spring compressed by the pin. 4. A mold body for defining a resin filling space for molding a synthetic resin molded product, a first gate for injecting a molten resin from a first predetermined position of the resin filling space, A second resin-filled space separated from the first predetermined position.
In a resin molding die having a second gate for injecting resin from a predetermined position, when the molten resin is injected from the first gate, the melt injected from the first gate in the resin filling space The resin is divided and two or more flows meet each other, and it is provided at a position facing the second gate across a third predetermined position where it is expected that a weld line will be formed. The small space for retracting the molten resin injected from one gate and the inlet on the resin filling space side of the small space are normally closed, and the molten resin is injected from the first gate to the first space. After the gate is closed, open the second gate,
A resin molding die comprising: a valve means for opening the inlet to guide the molten resin into the small space and withdrawing the molten resin. 5. A mold body for defining a resin filling space for molding a synthetic resin molded product, a first gate for injecting a molten resin from a first predetermined position of the resin filling space, A second resin-filled space separated from the first predetermined position.
In a resin molding die having a second gate for injecting resin from a predetermined position, when the molten resin is injected from the first gate, the melt injected from the first gate in the resin filling space It is confirmed that the pressure of the injected molten resin exceeds a predetermined value at a point closer to the first predetermined position than the third predetermined position where it is expected that the resin splits and two or more flows meet to form a weld line. A pressure detecting means for detecting and a position for facing the second gate across the third predetermined position and for retracting the molten resin injected from the first gate into the resin filling space. The small space and the inlet of the small space on the side of the resin filling space are normally closed, and when the pressure exceeds the predetermined value in response to the pressure detection means, the inlet is opened to melt the molten resin. Resin molding die, characterized in that it comprises a valve means for retracting guided to the small space the parts. 6. The pin, wherein the valve means is slidably arranged in the small space and has a head for closing an inlet of the small space, and the pressure detecting means is responsive to the pin and the pressure. The resin molding die according to claim 5, which has a coil spring compressed by the pin. 7. A second part of the molten resin injected from the second gate, wherein a part of the first tip of the molten resin injected from the first gate is in the resin filling space for molding the synthetic resin molded product. A method for reinforcing a weld line, wherein a recess for entering the tip is formed in the second tip, the method further comprising a point closer to the first gate than a predetermined position where the weld line is expected to be formed and communicates with the resin filling space. A small space with a valve for evacuating the molten resin injected from the first gate is provided, the first and second gates are opened, and the molten resin is simultaneously injected into the resin filling space from each gate. Then, after a lapse of a predetermined time, the first gate is closed, the valve of the small space is opened, and a part of the molten resin injected from the first gate is guided into the small space and retracted. Do Eldline reinforcement method. 8. A part of the first tip of the molten resin injected from the first gate at the first predetermined position in the resin filling space for molding the synthetic resin molded product is the second part of the resin space. In a weld line reinforcing method of forming a recess at the second tip for entering the second tip of the molten resin injected from the second gate at a predetermined position, the first and second gates are opened and Molten resin is simultaneously injected into the resin filling space, and two flows of the molten resin injected from the two gates meet in the resin space to form a weld line from a third predetermined position. It is detected whether or not the pressure of the molten resin injected at a point close to the first predetermined position exceeds a predetermined value, and after a predetermined time elapses after the first and second gates are opened and simultaneous injection is performed, Closes only the first gate when the pressure exceeds the predetermined value, and retracts the molten resin injected from the first gate to a point closer to the first predetermined position than the third predetermined position. A small space is provided to allow the valve means provided at the resin-filled space side inlet of the small space to be normally closed, and when the pressure exceeds the predetermined value due to the detection of the pressure. A method for reinforcing a weld line, characterized in that the valve means is opened and a part of the molten resin is guided into the small space and retracted. 9. The synthetic resin molded product to be molded has a through hole, and the molten resin injected from the first gate and the second gate splits around the through hole, respectively, and at least The method for reinforcing a weld line according to claim 7 or 8, wherein the positions of the first gate and the second gate are selected so that the weld line is formed by joining at two predetermined positions. 10. The first gate is provided at a position in contact with the through hole, and the second gate is in contact with the through hole,
The method of reinforcing a weld line according to claim 9, wherein the weld line is provided at a position facing the first gate, or the second gate is provided at a position contacting an outer periphery of the resin filling space and facing the first gate. 11. A molten resin injected from a first gate in a resin filling space for molding a synthetic resin molded article having a through hole is shunted around the through hole, and they are merged with each other. In a weld line reinforcing method in which a recess for allowing a part of the tip of the other to enter the other tip is formed in the one tip, a predetermined position where the weld line is expected to be formed is communicated with the resin filling space. A small space with a valve for evacuating the molten resin injected from the first gate is provided at a point near the first gate, and the first gate is opened to allow the resin filling space from the first gate. The molten resin is injected into the container, and after a lapse of a predetermined time, the first gate is closed and a predetermined position where the weld line is expected to be formed is sandwiched,
One of the molten resin injected from the first gate is opened by opening the second gate at a position facing the first gate to further inject the molten resin into the resin filling space and opening the valve in the small space. A method for reinforcing a weld line, characterized in that the portion is guided into the small space and retracted. 12. A first resin member at a first predetermined position in a resin filling space for molding a synthetic resin molded product having a through hole.
In the weld line reinforcing method, the molten resin injected from the gate is branched around the through hole, and they are merged to form a recess at the one tip so that a part of the one tip enters the other tip. , Opening the first gate, injecting molten resin from the first gate into the resin filling space, and two or more shunts of the molten resin injected from the first gate meet in the resin space, It is detected whether or not the pressure of the injected molten resin at a point closer to the first predetermined position than the second predetermined position where a weld line is expected to be formed exceeds a predetermined value, and the first gate is opened to perform simultaneous injection. After a lapse of a predetermined time, or when the pressure exceeds the predetermined value, the first gate is closed and the second predetermined position is sandwiched,
The second gate at a position facing the first gate is opened to further inject the molten resin into the filling space, and the first gate is located at a point closer to the first predetermined position than the third predetermined position. A small space for evacuating the injected molten resin is provided, and the valve means provided at the inlet of the small space on the side of the resin filling space is normally closed, and the pressure is detected by detecting the pressure. A weld line reinforcing method, characterized in that, when a predetermined value is exceeded, the valve means is opened and a part of the molten resin is guided into the small space and retracted. 13. A shunt of the molten resin injected from a first gate provided on the thick portion side in a resin filling space for molding a synthetic resin molded product having a thick portion and a thin portion. A method for reinforcing a weld line, wherein a recess for allowing a part of one tip to enter the tip of another branch is formed at one tip of the branch, wherein the weld line is formed by communicating with the thin portion of the resin filling space. A small space with a valve for evacuating the molten resin injected from the first gate is provided at a position facing the first gate across a predetermined position where the first gate is placed. Open and inject the molten resin from the first gate into the resin filling space. After a predetermined time elapses, the first gate is closed, and the weld line is expected to be sandwiched between the predetermined positions. Small space A second gate and a third gate provided at the position facing the inlet of the thick wall portion and opening the second and third gates to inject the molten resin into the resin filling space from the second and third gates; A method for reinforcing a weld line, characterized in that the valve in a small space is opened and a part of the molten resin injected from the first gate is guided into the small space and retracted. 14. A molten resin injected from a first gate in a resin filling space for molding a synthetic resin molded product having a thick portion and a thin portion and at a first predetermined position of the thick portion. In a weld line reinforcing method for forming a recess at one end of the shunt to allow a part of one end of the shunt to enter the tip of another shunt, the first gate is opened, and the resin is removed from the first gate. The molten resin is injected into the filling space, and it is detected whether or not the pressure of the injected molten resin in the thin portion in the resin space exceeds a predetermined value, and the predetermined time elapses after the first gate is opened and injected. Afterwards, or when the pressure exceeds the predetermined value, the first gate is closed, at a position facing the inlet of the small space across a position where the weld line is expected to be formed, and Provided in the thick part The second and third gates are opened to inject the molten resin from the second and third gates into the resin filling space, and the molten resin is injected at a point closer to the first predetermined position than the third predetermined position. A small space for evacuating the molten resin injected from the first gate is provided, and the valve means provided at the inlet of the small space on the resin filling space side is normally closed to detect the pressure. A weld line reinforcing method, wherein when the pressure exceeds the predetermined value, the valve means is opened to guide a part of the molten resin into the small space and to withdraw.