JPH0976288A - Injection molding method and injection molding die - Google Patents

Abstract

(57) Abstract: [PROBLEMS] To provide an injection molding method in which a substantially uniform force acts on a mold or the like both during mold clamping and during injection, and can be molded even in a narrow space. Melting into a cavity (44, 45, 44 ', 45') formed in a fixed mold (20) and two slide molds (40, 40 ') divided into approximately equal parts. When a primary molded product (A, B, A ′, B ′) is molded by injecting a resin, an even number of molded products are formed at a position with the substantially central axis portion of the fixed mold (20) as the center of symmetry. Primary molded products (A, B,
When A ', B') is solidified, slide mold (40, 4,
0 ') to slide the primary molded product (A, B, A',
B ') are butted against each other, and molten resin is injected into the butted parts to form a primary molded product (A, B, A', B ')
Also in the case of integrally molding, the fixed mold (20) is molded at a position with the substantially central axis portion as the center of symmetry.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to molding a primary molded product by a movable mold and a fixed mold, and then moving the movable mold with respect to the fixed mold to abut the primary molded product, and The present invention relates to an injection molding method for injecting a molten resin into a butted portion to integrate a primary molded product to obtain a molded product, and an injection molding die used for carrying out this method.

[0002]

2. Description of the Related Art As a method for producing a synthetic resin hollow molded article, a method using an injection molding machine is known. When manufacturing a hollow molded product with an injection molding machine, the hollow molded product is molded as a half-hollow molded product or a split body in the primary molding, and the split surfaces are butted to each other in the secondary molding.
Then, one hollow molded product is manufactured by heating or welding. To carry out this injection molding method, as shown schematically in FIG. 4A, a mold composed of a fixed mold 50, a slide mold 60, etc. is used. The slide die 60 is provided so as to be slidable in the vertical direction in the figure with respect to the fixed die 50, and two cores 61 and 62 are formed on the parting line side thereof at a predetermined interval. Below the cores 61 and 62, two recesses 63 and 64 are similarly formed at predetermined intervals. The fixed mold 50 includes the core 6 of the slide mold 60.
Recesses 51 and 52 are formed corresponding to the recesses 1 and 62, and cores 53 and 54 are formed corresponding to the recesses 63 and 64 of the slide mold 60. Therefore, these cores 61, 62 and 53, 54 and the recesses 51, 52, 63, 64 form four cavities 71 to 74. And sprues 75-78 are placed in these cavities 71-74.
Are in communication with each other.

Therefore, the mold is clamped in the state shown in FIG. 4A, and the molten resin is sprued on the sprue 75 of the fixed mold 50.
When injected into the cavities 71 to 74 from ~ 78, semi-hollow molded products a, b, a ', b'which are primary molded products are molded by these cavities 71 to 74. Although not shown in the figure, the movable platen is opened to slide the slide mold 60 upward by the piston cylinder mechanism 65, and as shown in FIG. 4B, the semi-hollow molded product a,
When the flange portions of b, a ′, b ′ are butted, and the mold is clamped and the molten resin is injected from the sprues 79, 80, the semi-hollow molded products a, b, a ′, b ′ are joined at the flange portion and hollow. The molded product is molded. Open the movable metal plate,
A hollow molded product is obtained by protruding the ejector pin.

[0004]

According to the above injection molding method, the slide mold 60 is slid with respect to the movable mold 50 to form semi-hollow molded products a, b, which are molded by primary molding.
Since a hollow molded product can be obtained by abutting a'and b'and injecting a molten resin by secondary molding, there is an advantage that each step can be automated and the hollow molded product can be mass-produced. In addition, a pair of semi-hollow molded products a, b,
Since a'and b'are molded by injection molding, it has a feature that a hollow molded product having a complicated shape can be manufactured. However, there is a drawback that an unbalanced load acts on the fixed mold 50, the slide mold 60, and the like. That is, when the mold clamping force and the injection pressure are made to uniformly act on the fixed mold 50 and the slide mold 60 at the primary molding position shown in FIG. 4A, the slide mold 60 is moved. In the secondary molding position in which the core 50 is slid upward with respect to the mold 50, the lower cores 53 and 54 are in an idle state and are not balanced, as shown in FIG. On the contrary, if a balance is provided at the secondary molding position, an eccentric load acts in the primary molding state. In this way, when an imbalanced load acts on the fixed mold 50 and the slide mold 60, the mold 50,
Problems will occur not only in 60 itself, but also in the molded product. For example, if an unbalanced load is applied, the molds 50, 60, etc. will be damaged, and the mold clamping device will be unevenly worn, so that the molds 50, 60, etc. cannot be used at an early stage. Further, if uneven wear occurs, a precise molded product cannot be obtained. Furthermore, the conventional slide mold 60 has a long slide distance,
It also has the drawback of requiring a large installation space. The present invention
It is an object of the present invention to provide an injection molding method which solves the above-mentioned problems and an injection molding die which is directly used for carrying out this method. Specifically, a metal mold is used both at the time of mold clamping and at the time of injection. It is an object of the present invention to provide an injection molding method and an injection molding die that allow substantially uniform force to act on a mold and the like and can mold even in a narrow space.

[0005]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a method of injecting a molten resin into a cavity formed in a fixed mold and a moving mold divided into substantially equal parts.
A primary molding step of molding a secondary molded article, and after the primary molding step, the moving mold is moved with respect to the fixed mold to abut the primary molded articles with each other, and the molten resin is applied to the abutted portion. And a secondary molding step of integrating the primary molded articles with each other. At the time of the primary molding step, an even number of primary moldings are performed at positions where the substantially central axis portion of the fixed mold is the center of symmetry. The product is molded, and is molded at a position with the substantially central axis portion of the fixed mold centered symmetrically even in the secondary molding step. According to a second aspect of the present invention, there is provided a mold comprising a fixed mold and a moving mold which is divided into substantially equal parts, wherein the moving mold is primarily molded with respect to the fixed mold. The cavity formed by the fixed mold and the movable mold is movably provided so as to take a position and a second position for the secondary molding, and a substantially central shaft portion of the fixed mold is formed. An even number is arranged as the center of symmetry. The invention according to claim 3 is configured such that the movable mold divided into substantially equal parts according to claim 2 is a first and second slide mold that slides in parallel with a parting line. Therefore, in molding, a fixed mold and a movable mold, which is divided into substantially equal parts, are used. The moving mold is set to the first position for primary molding with respect to the fixed mold, and molten resin is injected into an even number of cavities to mold an even number of primary molded products, for example hollow products. At this time, since an even number of cavities are arranged with the substantially central axis portion of the fixed mold as the center of symmetry,
Unbalanced load does not work. After cooling and solidification, the moving molds are moved to the second position, for example, in the state where the primary moldings are left in the fixed mold and the moving mold. As a result, the primary mold product of the fixed mold and the primary mold product of the movable mold are butted. Secondary molding is performed at the second position, and the primary molded product is integrated to obtain a molded product. Since this second position is also a position with the substantially central shaft portion of the fixed mold as the center of symmetry, an eccentric load does not act. Open the moving mold and take out the molded product. Molding is performed by repeating the above operation.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION A mold for molding a hollow molded article and a molding method using this mold will be described below as examples of the present invention. As shown in FIG.
The mold according to this embodiment is composed of a fixed plate 1 located on the left side in the figure, a fixed mold 20 fixedly attached to the fixed plate 1, divided into approximately equal parts, and vertically in the figure. First, which is designed to be slidably driven,
The second slide mold 40, 40 ', a movable plate 46 for driving the slide molds 40, 40' in the mold opening direction, and the like.

[0007] The fixed plate 1 is attached to a substantially central shaft portion of the fixed plate 1.
A sprue 2 is provided so as to traverse. Also,
As shown in (b) of FIG. 1, the fixed platen 1 has first and second runners 3 and 4 symmetrically extending in the vertical direction in the figure with the sprue 2 as a center. Has been formed. Further, the fixed platen 1 is provided with a sprue switching device 5 for switching the sprue 2 to the first and second runners 3 and 4. The sprue switching device 5 includes a cylinder 6 having a semicircular cross section, which is formed in a direction perpendicular to the plane of FIG. 1A, a valve body 7 slidably guided by the cylinder 6, and a valve body 7. 7 and a piston cylinder device 8 for driving the device 7.

As shown in FIG. 2 (a), the valve body 7 has an overall shape of a cylinder divided into two in the axial direction. The lower surface 7 ′ is in contact with the parting surface of the fixed mold 20 and slides. First and second resin passages 9 ′ and 12 are formed at predetermined intervals on the lower surface 7 ′ of the valve body 7 so as to cross the valve body 7 and cut to a predetermined depth. And the 1st through-hole 9 is opened in the 1st resin path 9 '. A groove 11 having the same depth extends in the axial direction from the second resin passage 12, and the second through hole 1 is formed at the end of the groove 11.
0 is opened. Therefore, when the valve body 7 is set to the first position shown in (b) and (c) of FIG. 2, the sprue 2 of the fixed plate 1 is aligned with the first through hole 9 and the first through hole 9 is formed.
Communicate with the first runner 3. Piston cylinder device 8
Drive the valve body 7 in the direction of the chain line, and
As shown in (e), the sprue 2 has the second through hole 1
In the second position aligned with 0, the sprue 2 communicates with the second runner 4 via the second through hole 10, the concave groove 11 and the first resin passage 12. In this way, the valve body 7 has a shape in which the cylinder is divided into two in the axial direction, and the first and second resin paths 9 ′, 1
Since 2 is open at the bottom, the runner can be taken out by opening the fixed mold 20. If the hot runner is used, the sprue switching device 5 can be simply constructed.

A first core 21 and a first core 21 are provided at a vertical center position of the fixed mold 20, that is, at a position above the sprue 2.
And a recess 22 of the same are provided at a predetermined interval. The second core 23 and the second core 23 are provided below the sprue 2.
Similarly, the recesses 24 are provided at a predetermined interval. The first core 21 and the second core 23 are formed at positions equidistant from the center position where the sprue 2 is provided, and the first and second recesses 22 and 24 are also arranged at positions equidistant. Has been formed. Although not shown in the drawing, the cores 21 and 23 and the recesses 22 and 24 are also balanced in the horizontal direction. Since they are symmetrically provided in this way, an eccentric load does not act on the fixed mold 20 and the like when the mold is clamped and when the primary and secondary molding is performed.

A first sprue 25 communicating with the first runner 3 is opened at the top surface of the first core 21, and the first recess 2 is formed.
A second sprue 26, which is also in communication with the first runner 3, opens at the bottom of the second runner 3. Similarly, a third sprue 27 communicating with the first runner 3 is provided on the top surface of the second core 23.
And a fourth sprue 28 that is also in communication with the first runner 3 is opened at the bottom of the second recess 24. The fixed mold 20 is further provided with first and second sprues 29 and 30 for secondary molding. The first and second sprues 29 and 30 for secondary molding communicate with the second runner 4.

The slide mold is composed of first and second slide molds 40 and 40 'which are divided at a substantially central portion in the vertical direction. Then, the first slide mold 40 located above is provided with a first recess 41 that forms a pair with the first core 21 and the first recess 22 of the fixed mold 20, and a first core 42. ing. Thereby, the first and second semi-hollow molded products A, between the fixed mold 20 and the first slide mold 40,
First and second cavities 44 and 45 for forming B are formed. Further, the second slide mold 40 ′ located below is also provided with a second recess 41 ′ that is paired with the second core 23 and the second recess 24 of the fixed mold 20, and a fourth core 42. 'And are formed respectively. This allows
Similarly, third and fourth cavities 44 'and 45' for molding the third and fourth semi-hollow molded products A'and B'are formed.

The first slide mold 40 is vertically driven by a piston cylinder device 45 which is a drive device, and the second slide mold 40 'is similarly moved downward and upward by a piston cylinder device 45'. It is designed to be driven by. Further, well-known ejector pins 50 and 50 ′ face the bottoms of the first and second recesses 41 and 41 ′, and these ejector pins 50 and 50 ′ are attached to the ejector plate 5
The first and third cavities 44, 44 'by 10, 51'
It is designed to stick out inside.

Next, using the fixed mold 20 and the first and second slide molds 40, 40 ', the first to fourth semi-hollow molded products A, B, A', B are subjected to primary molding. 'Molded,
Then, a molding method for molding a hollow molded article by a secondary molding method in which a molten resin is injected around the periphery will be described. First,
The second slide mold 40, 40 'is slid to the first position shown in FIG. Also,
The valve element 7 of the sprue switching device 5 is also switched to the first position shown in (b) and (c) of FIG. Then, the molten resin for primary molding is injected from the sprue 2 of the fixed mold 1 as is conventionally known. The molten resin flows from the sprue 2 of the fixed plate 1 to the first through hole 9 of the valve body 7 of the sprue switching device 5,
Through the runner 3 and the first to fourth sprues 25 to 28, and injection-filled into the first to fourth cavities 44 to 45 '.
As a result, the first to fourth primary semi-hollow molded products A, B,
A'and B'are molded. The state where the primary molding is completed is shown in FIG.

Waiting for cooling and solidification, the movable plate 46 and the first and second plates
Open the slide molds 40, 40 'of FIG. Then, the first slide mold 40 is slid upward by the piston cylinder device 45, and the opening of the first semi-hollow molded product A is aligned with the opening of the second semi-hollow molded product B. Move to position 2. Second slide mold 40 '
Is slid downward by the piston cylinder device 45 ′ and moved to the second position where the opening of the third semi-hollow molded product A ′ is aligned with the opening of the fourth semi-hollow molded product B ′. Then clamp the mold. The state where the mold is clamped in the second position is shown in FIG. In this state,
The open ends of the first to the first semi-hollow molded products A to B ′ are butted against each other. In addition, the valve body 7 of the sprue switching device 5
To the second position.

A molten resin for secondary molding is injected from an injection machine. The molten resin reaches the second runner 4 through the sprue 2 of the fixed plate 1, the second through hole 10 of the valve body 7 of the sprue switching device 5, the concave groove 11, and the second resin passage 12, and The first and second sprues 29 and 30 for secondary molding are injected to the abutting portion. As a result, the first to fourth primary semi-hollow molded products A, B and A ′, B ′ are integrated respectively. The integrated state is shown in FIG. Waiting for cooling and solidification, movable plate 46 and first and second slide dies 40, 4
Open 0 '. The surface area of the primary semi-hollow molded products A to B'includes
Although not shown exactly in the figure, there is a difference and the movable metal plate 46
When is opened, the integrated molded article is opened toward the first and second slide molds 40 and 40 '. The molded product is ejected by the ejector pins 50 and 50 '. The above operation is repeated to mold.

The present invention can be implemented in various forms without being limited to the above embodiments. For example, in the above embodiment, the slide molds 40 and 40 'are adapted to slide in the vertical direction to take the first position and the second position, but instead of sliding, the slide molds 40 and 40' are respectively replaced. It is also possible to take the first and second positions even when rotating. Further, in the above-mentioned embodiment, the primary hollow molded products A to B'are molded so that there is no flange at the peripheral edge of the opening, but it is desirable to mold them so as to have a flange. When the flanges are integrally molded, the molten resin can be injected between the flanges in the secondary molding, so that a molded product having a high bonding strength can be obtained. In addition, in the above embodiment, an example of obtaining a hollow molded product from the first to fourth primary semi-hollow molded products A to B ′ has been described, but it is also clear that molded products other than the hollow molded product can be molded in the same manner. is there.

[0017]

As described above, according to the present invention, the molten resin is injected into the cavity formed in the fixed mold and the moving mold divided into substantially equal parts to mold the primary molded product. 1
At the time of the next molding, an even number of primary moldings are molded at positions where the substantially central axis portion of the fixed mold is symmetrically centered, so that even loads are applied to the fixed mold and the moving mold at the time of molding. The effect peculiar to the present invention can be obtained. In addition, the secondary molding in which the moving mold is moved with respect to the fixed mold, the primary molded products are butted against each other, and the molten resin is injected into the butted parts to integrate the primary molded products, Since it is performed at a position with the substantially central axis portion of the mold as the center of symmetry, the unbalanced load does not act even during the secondary molding. Therefore, according to the present invention, the probability of failure of the mold and the like is reduced, and uneven wear of the mold clamping device is less likely to occur. Therefore, the mold or the like cannot be unusable at an early stage, and the precision of the molded product does not deteriorate. According to another invention in which the movable die is composed of the first and second slide dies, the sliding distance is short and the installation space is narrow because the two slides are separated in comparison with the conventional sliding distance. The effect that it can be placed is further obtained.

[Brief description of drawings]

FIG. 1 is a view showing an example of an embodiment of a mold of the present invention,
(A) is a schematic cross-sectional view showing the whole, and (B) is a plan view showing a sprue portion.

FIG. 2 is a view showing a sprue switching device, in which (a) is a perspective view of a valve body, (b) is a plan view when the valve body is in the first position, and (c) is a side sectional view thereof. , (D) is a plan view when the valve body is in the second position, and (e) is a side sectional view thereof.

FIG. 3 is a diagram showing a molding state using the mold shown in FIG. 1, in which (a) shows a state in which the primary molding is finished,
And (b) is a sectional view showing a state in which the secondary molding has been completed.

FIG. 4 is a view showing a molding state by a conventional die, in which (a) is a primary molding and (b) is a sectional view showing a secondary molding state.

[Explanation of symbols]

 1 Fixed plate 20 Fixed mold 25-28 1st-4th sprue 40, 40 '1st, 2nd slide mold 44, 45, 44' 45 '1st-4th cavities A, B, A', B '' The first to fourth semi-hollow molded products

Claims (3)

[Claims] 1. A molten resin is placed in cavities (44, 45, 44 ', 45') formed in a fixed die (20) and a moving die (40, 40 ') divided into substantially equal parts. A primary molding step of injecting and molding a primary molded article (A, B, A ', B'); and, after the primary molding step, the moving mold (40, 40 ') is fixed to the fixed mold ( 20) and the primary molded products (A, B, A ', B') are abutted against each other, and molten resin is injected into the abutted parts to inject the primary molded products (A, B, A '). , B ′) are integrated into a secondary molding step, and an even number of primary molded articles are placed at positions at which the substantially central axis portion of the fixed mold (20) is a symmetrical center during the primary molding step. (A, B, A ', B') is molded, and is molded at a position with the substantially central axis portion of the fixed mold (20) as the center of symmetry even during the secondary molding step. An injection molding method comprising: 2. A mold comprising a fixed mold (20) and a moving mold (40, 40 ′) divided into substantially equal parts, wherein the moving mold (40, 40 ′) is Fixed mold (2
0) is provided so as to be movable so as to have a first position for primary molding and a second position for secondary molding, and the fixed mold (20) and the movable mold (40, 40). ')
Cavities (44, 45, 44 ', formed by
45 ') is arranged in an even number with the substantially central axis portion of the fixed mold (20) as the center of symmetry.
Injection mold. 3. The moving mold (40, 40 ') divided into substantially equal parts according to claim 2 is a first and a second slide mold (40, 40') that slides parallel to a parting line. An injection mold.