JP3047213B2 - Method for molding hollow molded article and mold for molding hollow molded article - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a primary molding step of injecting a molten resin into cavities formed in a stationary mold and a movable mold to form at least one pair of primary semi-hollow molded articles, After this primary molding step, the movable mold is moved with respect to the fixed mold to butt the pair of primary semi-hollow molded products together, and the molten resin is injected into the abutted portion to form the pair of primary semi-hollow molded products. The present invention relates to a method for molding a hollow molded article, which is used to obtain a hollow molded article from a secondary molding step of integrating the articles, and a mold for molding a hollow molded article used for performing the method.

[0002]

2. Description of the Related Art As a method for producing a hollow molded article made of synthetic resin, a production method using an injection molding machine is known. When manufacturing a hollow molded article by an injection molding machine, the hollow molded article is molded as a half semi-hollow molded article or a divided body in the primary molding, and the divided surfaces are abutted in the secondary molding,
Then, a molten resin is injected into the butted portion to produce one hollow molded product.

[0003] A mold used for carrying out this injection molding method is, as schematically shown in FIG.
And a slide mold 60. In the fixed mold 50, one semi-hollow molded product A 'is molded, and in the slide mold 60, the other semi-hollow molded product B' is molded. Therefore, although not shown in the drawing, the semi-hollow molded products A ′ and B ′ are primarily molded so as to have the joining space portions a and b around the slide mold 60 in the first position, and Slide mold 6 after solidification
When 0 is slid to the second position shown in the figure, the pair of semi-hollow molded articles A ′, B ′ are butted at the joining space portions a, b. Therefore, the molten resin is injected from the sprue 52 through the gate 53 to the joining space portions a and b,
After the next molding, the pair of semi-hollow molded products A ′ and B ′ are joined in the joining space portions a and b, and the hollow molded product is molded. By opening the movable platen and projecting the ejector pins, a hollow molded product is obtained.

[0004]

According to the above-mentioned injection molding method, the slide mold 60 is slid with respect to the movable mold 50, and a pair of semi-hollow molded articles A 'and B' molded by primary molding. By injecting molten resin into the joining space portions a and b by secondary molding, a hollow molded product can be obtained. Therefore, there is an advantage that each step can be automated and the hollow molded product can be mass-produced. Further, since the pair of semi-hollow molded products 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, the strength of the joint may be weak. That is, since the gate 53 is provided at a right angle to the joining space portions a and b, the molten resin is used during the secondary molding to form the inner pieces a ′ and b ′ that constitute the joining space portions a and b.
At right angles. Therefore, when the injection pressure of the molten resin is increased, the inner pieces a ′ and b are pierced and leak into the hollow molded article. Therefore, the secondary injection pressure is kept constant. As a result, the strength of the joint is not always large. Also, since the molten resin hits the joining space portions a and b at a right angle, and the injection pressure is kept relatively low, the flow of the molten resin in the joining space portions a and b is poor, and the number of gates must be increased. There is also a problem that the entire circumference is not joined. Therefore, the present invention provides a method for molding a hollow molded article and a hollow molded article used for carrying out this method, in which the strength of the joining portion is large and the joining can be performed even with a small number of injection points of the molten resin for secondary molding. An object of the present invention is to provide a molding die.

[0005]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides at least one pair of primary semi-hollow moldings by injecting molten resin into cavities formed in a fixed mold and a movable mold. A primary molding step of molding the article, and after the primary molding step, the movable mold is moved with respect to the fixed mold so that the pair of primary semi-hollow molded articles abut each other and to the abutted portion. In a molding method for obtaining a hollow molded product from a secondary molding process of integrating a pair of primary semi-hollow molded products by injection-filling a molten resin, in the secondary molding process, the molten resin injected into the butted portion is Injection direction and
The injection filling is configured such that the angle formed by the tangent at the injection filling point of the butted portion is smaller than 90 °. According to a second aspect of the present invention, at the time of the second molding step of the first aspect, the abutted portion is injected and filled with the molten resin from a plurality of locations. The invention according to claim 3 comprises a stationary mold and a movable mold movably provided with respect to the stationary mold, and these molds have at least one pair of primary semi-hollow moldings. A mold provided with a cavity for molding an article, wherein a gate for secondary molding is opened in a peripheral wall near an opening of the cavity, and an axis of the gate and an opening in the peripheral wall are formed. The angle formed by the tangent at the point is smaller than 90 °, and the invention according to claim 4 is characterized in that a runner for secondary molding is provided outside the peripheral wall near the opening of the cavity according to claim 3. A plurality of secondary molding gates are provided from the secondary molding runner.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with respect to a mold for molding a hollow molded article and a method for molding a hollow molded article using this mold. As shown in FIG. 1A, a mold according to the present embodiment includes a fixed platen 1 located on the left side in the figure and a fixed mold 20 fixedly attached to the fixed platen 1. And a slide mold 40 which is slidably driven in the vertical direction in the figure. A driving device for driving the slide mold 40 in the vertical direction in the figure, a movable plate for driving the slide mold 40 in the mold opening direction, a slide mold 40
Are not shown in the figure.

A substantially central shaft portion of the fixed platen 1
The sprue 2 is provided so as to traverse. Also,
As shown in (b) of FIG.
A runner 3 for primary molding extending symmetrically with respect to the sprue 2 in the vertical direction in the figure and a runner 4 for secondary molding extending upward are formed. These runners 3 and 4 communicate at a sprue switching device 5 described later. Furthermore, one sprue 2 is attached to the fixed platen 1.
A sprue switching device 5 for switching between a runner 3 for the next molding and a runner 4 for the secondary molding is provided. The sprue switching device 5, as shown in FIG.
In FIG. 1A, a cylinder 6 having a semicircular cross section formed in a direction perpendicular to the paper surface, a valve element 7 slidably guided by the cylinder 6, and a piston cylinder device for driving the valve element 7 8.

As shown in FIG. 2A, the valve body 7 has a shape obtained by dividing a cylindrical body into two parts, and the lower surface 7 ′ thereof is in contact with the parting surface of the fixed mold 20. It is designed to move. A first resin passage 9 ′ is formed in the lower surface 7 ′ of the valve element 7 and opened to the lower surface so as to cross the valve element 7. A first through-hole 9 is formed in the first resin passage 9 'perpendicularly to the plane of FIG. A second through hole 10 is provided at a predetermined distance from the first through hole 9 in the axial direction. This second through hole 10
Are also provided in the concave groove 11 for the resin passage at substantially the same depth as the first resin passage 9 ′. This concave groove 11 communicates with a side opening 12 parallel to the paper surface.

Therefore, the valve element 7 is shown in FIG.
In the first position shown in (c), the sprue 2 of the fixed platen 1 is aligned with the first through hole 9, and the sprue 2 is connected to the runner 3 for primary molding through the first resin passage 9 '. Communicate with When the valve body 7 is driven by the piston cylinder device 8 in the direction of the dashed line and the sprue 2 is at the second position where the sprue 2 is aligned with the second through-hole 10, the sprue 2 is And runner 4 As described above, the first and second runners 3 and 4 are provided on the party surface of the fixed platen 1, and the first resin passage of the valve body 7, the concave groove 11, and the like are opened downward, that is, toward the parting line P. Therefore, when the fixed mold 20 is opened, sprues, runners and the like are taken out. In addition,
If a hot runner is used, the sprue switching device 5 that switches between the first and second runners 3 and 4 can be easily configured.

At a position above the fixed die 20, a fixed-side concave portion 21 having a rectangular side surface and having a predetermined depth is formed on the parting line P side. This fixed side recess 21
Is the bottom wall 22, the peripheral wall 2 rising from the bottom wall 22
2 ′, a flange wall 23 extending outward from the upper end of the peripheral wall 22 ′, and a second rising from the flange wall 23.
Of the peripheral wall 24. And the second peripheral wall 24
, A gate for secondary molding is opened. The fixed-side recess 21 cooperates with a slide-side core of a slide mold 40 to be described later to constitute a first cavity for forming a first semi-hollow molded product, and includes a flange wall 23 and a second peripheral wall 24.
Cooperates with the annular core of the slide mold 40 during the primary molding to form a part of the joint space.

A fixed core 25 of a predetermined size having a rectangular side surface and protruding outward from the parting line P is formed below the fixed mold 20.
An annular core 26 is formed around the fixed core 25 so as to surround the fixed core 25 at a predetermined interval. The fixed-side core 25 cooperates with a slide-side recess of a slide mold 40 to be described later to constitute a second cavity for forming a second semi-hollow molded product.
Numeral 6 cooperates with the second peripheral wall of the slide mold 40 to form a joint space at the time of primary molding.

At a position above the slide mold 40, a slide-side core 41 having a square side surface protruding outward from the parting line P is formed. The slide-side core 41 constitutes a first cavity in cooperation with the fixed-side recess 21 of the fixed mold 20 and is smaller by the thickness of the hollow molded product. And at a certain interval around it,
An annular core 42 surrounds the slide-side core 41.
Are formed. The annular core 42 and the fixed mold 20
As shown in FIG. 3A, the flange wall 23 and the second peripheral wall 24 form a half of the above-mentioned annular joint space.

Below the slide mold 40, a slide-side recess 44 having a rectangular side surface opening toward the parting line P is formed. This slide side recess 44
Is the bottom wall 45, the peripheral wall 4 rising from the bottom wall 45.
5 ', a flange wall 46 extending outward from the upper end of the peripheral wall 45', a second rising from the flange wall 46.
Of the peripheral wall 47. This slide side recess 4
4 constitutes a second cavity for forming the second semi-hollow molded product in cooperation with the stationary core 25 of the stationary mold 20 described above. In addition, the flange wall 46 and the second
Peripheral wall 47 cooperates with the annular core 26 of the fixed mold 20 at the time of the primary molding to form a half of the joint space. The second peripheral wall 47 has no gate for secondary molding.

The stationary mold 20 has first and second primary moldings.
Are provided, and a sprue 33 for secondary molding is provided. First and second sprues 31, 3 for primary molding
One of the two 2 is connected to the runner 3 for primary molding described above. The other of the first sprues 31 is open to the bottom wall 21 ′ of the fixed-side recess 21, and the other of the second sprue 32 is open to the top of the fixed-side core 25. FIG. 1 (b) is a schematic side view seen from the parting line P side to show the runner and gate through which the molten resin flows during the secondary molding. As shown in FIG. Outside the second peripheral wall 24 of the fixed side recess 21, a second runner 3 for secondary molding is formed so as to surround the peripheral wall 24.
5 are provided. Then, in the illustrated embodiment, four gates 36, 36,...
At the opening point 39 of the peripheral wall 24.

The axis 3 of these gates 36, 36,...
, And tangents 38, 38,... Of the second peripheral wall 24 at the opening points 39, 39,.
θ are 90 ° or less.

Next, the first and second semi-hollow molded articles A and B are molded by primary molding using the fixed mold 20 and the slide mold 40, and a molten resin is injected into the periphery thereof. A molding method for molding a hollow molded article by the secondary molding method will be described. The slide mold 40 is slid to the first position shown in FIG. Further, the valve body 7 of the sprue switching device 5 is also switched to the first position shown in FIG. Then, a molten resin for primary molding is injected from the sprue 2 of the fixed platen 1 in a known manner. The molten resin is supplied 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, the runner 3 for the primary molding, and the first and second sprues 31 and 3 for the primary molding.
2, the first and second cavities 27 and 28 are injected and filled. The molten resin for the primary molding is indicated by dots in FIG. Thereby, the first and second primary semi-hollow molded products A and B in which the annular butting surface M, the flange portion F, the annular recess K and the like are integrally formed at the butted portions C and C are shown in the figure. Molded as is.

After cooling and solidification, the slide mold 40 is opened at a predetermined interval. Then, the slide mold 40 is moved to the second
The first semi-hollow molded product B is slid upward in a state where it is attached to the mold, and the butt portion C of the second semi-hollow molded product B is placed at the opening or butt portion C of the first semi-hollow molded product A. Move to a matching second position. Then clamp the mold. Further, the valve element 7 of the sprue switching device 5 is switched to the second position shown in (d) and (e) of FIG.
The state where the mold is clamped at the second position is shown in FIG. In this state, the annular butting surfaces M, M of the first and second primary semi-hollow molded products A, B abut, and a joint space S is formed between the flanges F.

A molten resin for secondary molding is injected from an injection machine. The molten resin is supplied to the sprue 2 of the fixed plate 1, the second through hole 10, the groove 11, the side opening 1 of the valve body 7 of the sprue switching device 5.
2, through the second runner 4, the secondary forming sprue 33 and the like, reach the secondary forming second runner 35, and are injected from the gates 36, 36,. At this time, as shown in FIG. 3C, the emission angles θ, θ,... Are the angles formed by the emission direction line J and the tangent T of the joining space S at the emission points P, P,. Is made to be 90 ° or less. By this secondary molding, the first and second semi-hollow molded articles A and B are integrated. The state of being integrated by the secondary molding is shown by bold diagonal lines in FIGS. After cooling and solidification, the slide mold 40 is opened. Although the surface area of the primary semi-hollow molded products A and B is not accurately shown in the figure, there is a difference, and when the slide mold 40 is opened, the integrated molded product is Opened with. The molded product is protruded by the ejector pin. 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 this embodiment, since a hollow molded article having a cubic shape is formed, the gate angle θ can be set to zero. That is, the primary semi-hollow molded article A,
When the injection and filling are performed from the corner of B, the injection direction becomes parallel to the sides of the primary semi-hollow molded products A and B, and the gate angle θ becomes zero. Further, a hollow molded article having a circular cross section can be formed. It is clear that the gate angle θ at this time is the angle formed by the axis of the gates 36, 36,... And the tangent at the opening point. Further, according to the present embodiment, the first and second semi-hollow molded products are composed of the main bodies having substantially the same shape.
A primary molded product having substantially no concave portion, such as a lid,
Can be joined by secondary molding. Further, it is clear that the shape of the joining space S is not limited to the embodiment. Also, the mold is not limited to the embodiment. For example, by increasing the number of cavities, a plurality of hollow molded products can be simultaneously molded using a single-sided mold. Further, the slide mold 40
It is also clear that the present invention can be practiced with a rotary mold that takes the first position and the second position by rotating instead of the above.

[0020]

As described above, according to the present invention, at least one pair of primary and semi-hollow molded articles is formed by injecting molten resin into the cavities formed in the fixed mold and the movable mold. After the molding step and the primary molding step, the movable mold is moved with respect to the fixed mold to butt the pair of primary semi-hollow molded articles with each other, and the abutted portion is injected and filled with a molten resin to form the pair. When obtaining a hollow molded product from the secondary molding process of integrating the primary semi-hollow molded product, at the time of the secondary molding process,
Injection and filling is performed so that the angle between the injection and filling direction of the molten resin injected into the butted portion and the tangent at the injection and filling point of the butted portion is smaller than 90 °, or oblique to the butted portion Therefore, even if the injection pressure for the secondary molding is increased, there is little danger that the molten resin for the secondary molding leaks from the abutted portion to the inside. Therefore, according to the present invention, a hollow molded article having a large bonding strength can be obtained. Further, since the injection pressure for the secondary molding can be increased, the flow path of the flow of the molten resin for the secondary molding can be lengthened. Therefore, according to the present invention, the number of gates for secondary molding can be reduced, and the effect of simplifying the structure of the mold can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of an embodiment of a mold according to the present invention;
(A) is a schematic cross-sectional view showing the slide mold opened,
(B) is a side view of (a) as viewed in the direction of harha.

FIGS. 2A and 2B are diagrams schematically showing an example of an embodiment of a sprue switching device, wherein FIG. 2A is a perspective view of a valve body, and FIG. A plan view of the switching device, (C) is a cross-sectional view thereof, and (D) is a second valve body.
Is a plan view of the sprue switching device when it is moved to the position of FIG.

FIG. 3 is a view showing a molding state using the mold shown in FIG. 1, and FIG.
(B) is a cross-sectional view schematically showing a state in the middle of the secondary molding, and (C) is a side view of (B) as viewed in the direction of harha.

FIG. 4 is a cross-sectional view illustrating a molding state using a conventional mold.

[Explanation of symbols]

1 fixed board 20
Fixed mold 21 Fixed side recess 25
Fixed side core 27 First cavity 28
Second cavity 31, 32 First and second sprues for primary molding 33 Sprue for secondary molding 35 Runner for secondary molding 36 Gate for secondary molding 40
Slide die 41 Slide side core 44
Sliding side recess A First semi-hollow molded product B Second semi-hollow molded product S Joining space

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-87315 (JP, A) JP-A-3-230924 (JP, A) JP-A-4-161313 (JP, A) JP-A 5- 342808 (JP, A) JP-A-5-342809 (JP, A) JP-A-6-91693 (JP, A) JP-A-6-179228 (JP, A) JP-A-8-34032 (JP, A) JP-A-4-25423 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B29C 45/00-45/84

Claims (4)

(57) [Claims] 1. A molten resin is injected into cavities (27, 28) formed in a fixed mold (20) and a movable mold (40) to form at least one pair of primary semi-hollow molded articles (A,
B) a primary molding step of molding, and after the primary molding step, the movable mold (40) is moved with respect to the fixed mold (20) to form a pair of primary semi-hollow molded articles (A , B) are butted against each other, and the butted portion (S) is injection-filled with a molten resin to form a pair of primary semi-hollow molded products (A, B) into a secondary molding process to obtain a hollow molded product. In the molding method, at the time of the secondary molding step, the injection filling direction (J) of the molten resin injected into the butted portion (S) and the tangent (T) at the injection filling point (P) of the butted portion (S) are obtained. Injection molding so that the angle (θ) is smaller than 90 °. 2. A method for molding a hollow molded article, comprising: injecting and filling a molten resin from a plurality of locations into abutted portions (S) during the secondary molding step according to claim 1. 3. A fixed mold (20) and a movable mold (40) movably provided with respect to the fixed mold, and these molds (20, 40) have at least A mold provided with cavities (27, 28) for molding a pair of primary semi-hollow molded articles (A, B), wherein a peripheral wall (24) near an opening of the cavity (27) is provided. , The gate (36, 36,...) For secondary molding is open, and the axis (3) of the gate (36, 36,.
7) and the tangent (3) at the opening point (39) of the peripheral wall (24).
8) a mold for molding a hollow molded article, wherein an angle (θ) formed by the mold is less than 90 °. 4. A runner (35) for secondary molding is provided outside the peripheral wall (24) near the opening of the cavity (27) according to claim 3, and the runner (35) for secondary molding is provided. )
, A mold for molding a hollow molded product in which a plurality of gates (36, 36,...) For secondary molding are branched.