JPS60145817A - Manufacture of hollow semispherical body and apparatus therefor - Google Patents

Abstract

PURPOSE:To obtain a hollow semispherical body whose quality is uniform, whose roundness is high and that has a three-layer structure, by rotating a core and/or a cavity of a mold for injection molding, and injecting a resin from a gate diverted from the central part of the mold. CONSTITUTION:A melted resin is injected into a molding space between a cavity 1 and a core 4 that is rotated via a driving shaft 12, gears 13, 14, and a main shaft 6 from a gate 3 diverted from the central part of the mold, turbulent flows are caused with the rotation of the core 4, and a hollow semispherical body is molded with a three-layer structure being formed due to the temperature difference between the cooled cavity 1 and an intermediate layer that is out of direct contact with the part directly engaged with the core 4. Then the rotation of the core 4 is stopped, and the molded item is removed by a stripper plate 15 and a stripper bush 16. Then this is sucked to perforated plate surfaces 19a, 20a by holders 19, 20 with vacuum sucking plates, shafts 21, 22 are rotated, an adhesive is added dropwise from an applicator 23 in the form of a needle, and the shafts 21, 22 are drawn together to join the open peripheries.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method and apparatus for manufacturing hollow hemispheres used for pin-bong balls, flush toilet floats, fishing floats, toys, etc.

Prior Art Conventional techniques for manufacturing hollow spheres using resin include blow molding,
There are methods such as a method in which hemispheres are manufactured by sheet homing and then fitted together, and a rotary molding method.

Problems to be Solved by the Invention According to the first blow molding method, thickness unevenness during molding is unavoidable, and burr occurs at the joint part of the mold. The disadvantage is that the strength of the part is reduced.

According to the so-called pressure forming method in which the hemispheres are manufactured and then fitted together by second sheet forming, uneven thickness occurs as in the blow molding method described in Clause 1, and the roundness of the sphere cannot be changed and the fitting is caused. There were also problems with workability during bonding.

According to the third rotational molding method, there is no uneven thickness reduction than in the first and second methods, and a sphere with roundness can be obtained, but there are restrictions on the materials suitable for rotational molding.
In addition, problems still remain regarding the occurrence of flakes on the joint surfaces of the molds and workability during fitting and adhesion.

In particular, pinbong balls are manufactured by the second method using celluloid sheets, but they still have the same problems as the second method.

That is, in the method of forming a hemisphere from a sheet, it is impossible in principle to obtain a uniform film thickness over the entire spherical surface, and therefore uneven thickness tends to occur.

If there is uneven thickness on the membrane surface, it will not be possible to obtain the normal bounce required for a bing pong ball.

In addition, since the hemispheres are cut out from the sheets and joined together, only small-line cut surfaces can be obtained, which makes bonding with dope cement in the subsequent process extremely difficult. It was not possible to obtain a Bing Pong ball with extremely roundness.

Furthermore, since the dope cement bonding method uses the same material as the material to be bonded as a solvent, the solvent acts on the cellulose base material, causing internal distortion, strength deterioration, and other negative causes such as shrinkage. .

Means to Solve the Problems As a result of intensive research, the inventors of the present invention devised a method of producing a hollow hemisphere using a new injection method, and were unable to solve the above-mentioned problems.

That is, the present invention involves rotating either or both of an injection mold consisting of a cavity or a core, and injecting resin into the mold through a gate located at a position offset from the center of the mold. While molding a hemisphere, the resin is compressed while rotating the mold, or after the mold rotation is stopped, the mold is rotated in the opposite direction to form three layers of resin in the hollow hemisphere. The first invention is a method for manufacturing a hollow hemisphere characterized by forming a structure, and an injection molding mold having a function of rotating one or both of the molds having a gate at a position offset from the center. The second invention is an injection molding device configured with a mold.

Effects of the Invention According to the manufacturing method and apparatus according to the present invention, a hollow hemisphere is made by an injection molding method, so not only can the resin material used as the material be freely selected, but also a perfect circle with uniform flesh quality can be produced. It is possible to move around the hollow hemisphere, and compared to the conventional method of making a hemisphere using pressure molding and fitting and bonding, which limits the shape of the joint surface, it is possible to freely select a shape for the application. It not only improves workability by improving the adhesive, improves joint strength, and improves roundness accuracy, but also allows you to freely select the adhesive. The decrease in strength due to strain can be eliminated by rotating either the mold cavity or the core, or both, to effectively create a three-layer structure between the membrane layers, resulting in high tensile strength, burst resistance, and fi impact resistance. It has the characteristic of being able to roam around a perfectly circular hollow hemisphere.

In any case, the most distinctive feature of the present invention is that injection molding is performed by virtually rotating either the cavity or the core of the mold, which has a gate located at a position offset from the center, or both.

Generally, due to the characteristics of injection, resin flows from the gate into the space between the cavity and the core, and it is common knowledge that internal distortion occurs along the flow of the resin. Normally, this internal strain is removed by annealing in a heating chamber, etc., but in the present invention, the cavity is removed by rotating the mold when injecting resin from the gate into the space between the cavity and the core. The molten resin that has entered the space between the core and the core causes a turbulent flow, and at the same time the mold surface is being cooled. However, this allows the membrane to effectively form a three-layer structure and exhibit high strength against tearing and tension.

However, since the resin is injected from the gate located at a position offset from the center of the mold, turbulent flow occurs throughout the entire molten resin, which allows the resin structure to be randomly oriented in multiple directions to be suspended. More efficient molding can be achieved by compressing the resin without rotating the mold when the mold is rotating, or by rotating the mold in the opposite direction after stopping the mold rotation.

Note that U.S. Pat. No. 340,970 describes a system in which the mold is rotated during injection molding, but this is for molding a container, and since the corners at the bottom of the container are not rounded, the molten resin does not flow in this area. Since the round corner stagnation does not cause uniform turbulent flow, it is not possible to change the molded product with good orientation.Furthermore, since the gate is provided in the center of the mold, the molten resin remains stationary in this part. This results in a molded product with even worse orientation and weaker strength, but since the present invention is molded into a hollow hemisphere and has a rounded shape as a whole, this together with the fact that the gate is offset from the center of the mold. There are no shortcomings at all.

As the resin used in the present invention, any resin can be used as long as it can be injection molded, and
For example, phenolic resin, urea resin, melamine resin, cellulose acetate, polyvinylidene chloride, methacrylic resin, polyamide, polyolefin such as polystyrene or polypropylene, polystyrene, styrene-acrylonitrile copolymer, acrylonitrile-butadiene-styrene copolymer, fluororesin, polycarbonate, polyether,
Saturated polyester or the like is used.

Example The present invention will be specifically described below with reference to the drawings.

As the injection molding machine used in the method and apparatus according to the present invention, a general-purpose molding machine is used in consideration of materials, precision, etc.
The mold is manufactured with consideration given to accuracy, roundness, etc., and the shape and surface condition of the joint surface.

However, since it is necessary to rotate either the cavity or the core, or both, the ones shown in FIGS. 1 to 4 are used. However, the illustrated one rotates the core.

FIG. 1 is a cross-sectional view of the mold portion, and FIG. 2 is a diagram showing the molds arranged in a four-speed manner.

In the injection mold, the cavity (1) is installed in the fixed side mold plate (2), and it is equipped with a gate (3), which is the same as in normal molds, from where the resin flows between the cavity and the core. Injected into space.

The rotating core (4), which forms a hemispherical space together with the cavity (1) as described above, is integrally formed with a main shaft (6) that is rotatably mounted on the movable mold plate (5). ,
The rear end of the main shaft (6) is connected to the receiving plate (
8) receives thrust.

(9') (10) is a Noso thrust roller hair ring.

The sprocket is driven via a chain from a motor (not shown) installed on the movable mold. (11)
drives the drive shaft (12), and the drive shaft (12) drives each main shaft (6) as its gear (13) is engaged with the gear (14) of each main shaft (6). , rotating core (
4) Rotate.

The rotating core (4) has a mushroom shape, and its constriction is supported by another core (4a), and together with the above-mentioned thrust roller hair rings (9) and (10), it is designed to withstand injection pressure sufficiently. It is being In addition, (15) is a stripper plate, and this has a stripper bush (16).

In addition, there is a runner and a stripper plate (17) between the fixed side mold plate (2) and the fixed side mounting plate (2a), so that the movable mold moves relative to the second fixed side mold and the core (4 ) forms a molding space together with the cavity. Others (18) are movable side mounting plates.

In the above mold, the cavity (1) is the rotating core (4
) to form a molding space, the drive shaft (1
2) through the gears (13) (14) and the main shaft (6), the °ζ core (4) is rotated and the gate (3) is rotated.
) is injected into the molding space.

At that time, the gate (3) is located at a position offset from the center of the mold.
As the rotating core (4) rotates, the molten resin that has entered the molding space creates a turbulent flow, and at the same time, as the mold is being cooled, there is a flow between the part that directly contacts the mold and the intermediate layer that does not directly contact the mold. Since it rotates while creating a temperature difference, the film is molded while effectively forming a three-layer structure.

At this time, the molten resin is injected into the molding cap from the gate (3) located at a position offset from the center of the mold, causing a turbulent flow throughout the molten resin, forming a hollow hemisphere oriented randomly in multiple directions. More efficient molding can be achieved by compressing the resin while rotating the mold, or by rotating the mold in the opposite direction after the mold has stopped rotating.

When the molding is completed, the rotary core (4) stops rotating and the molded product that leaves the cavity (1) is removed by the strip plate (15).

For example, the injection molding conditions described above are as follows.

Mold clamping force: 10 tons or more Injection pressure: 500 kg/cLa or more Core rotation speed: 5 Qrpm to 1000 rpm Rotating torque: 1 kgm to 20 kgm Mold temperature: 15°C
Injection time: 0.2 to 3 seconds Injection pressure: 500 to 600 kg/c+J Injection rate: 1
00 to 300 cc/S Extruder screw rotating machine 10 to 300 rpmI11 The shape of the core is a straight round bar shape following a spherical part as shown in Fig. 4, or a spherical part followed by a straight round bar shape as shown in Fig. 3. Subsequently, it is possible to form the core into a conical shape, but since the core must rotate while being subjected to considerable injection pressure, a shape as shown in FIG. 1 is preferable.

Next, the hollow hemispheres obtained by injection molding as described above are bonded together at their opening edges to form a hollow sphere.The joining method is as shown in Figure 5.6. methods are used.

That is, as shown in Fig. 5, a holder with a vacuum suction cup (1
9) Glue the hemispherical molded bodies (a) and (b) to (20) so that they fit together.

Perforated plate surface (19a) of holder (19) (20)
(20a) is formed into a hemisphere of the same shape, so the holder (19) (20a) is passed through the pipe from the vacuum pump.
) If the boxes (19b) (20b) in ) are evacuated, they will be easily adsorbed by the porous holes '1k (19a) (20a).

Each holder (19) (20) also has its shaft (21)
(22) is rotatable and can also be raised and lowered, so while rotating the shafts (21) and (22), a fixed amount is applied from the needle-shaped applicator (23) to either side of the opening edge of the hollow hemisphere. Then, one or both of the shafts (21) and (22) are brought close to each other to join the opening edges. In this case, even more uniform bonding can be achieved by changing the rotation.

The one shown in FIG. 6 uses an endless belt-shaped coating device instead of the injection needle-shaped coating device shown in FIG.

(24) is an endless belt stretched between rotating rollers (25) and (26), a part of which is immersed in an adhesive tank (27), and as it rotates, the part coated with adhesive It can be applied by directly contacting the opening edge of the hemisphere.

The hemispheres can be joined as described above to obtain a hollow sphere, but in addition to the above-mentioned adhesive application joining method, the shape of the joining surface can be freely tethered on the mold. Spin welding, high-frequency bonding, ultrasonic bonding, and doped cement bonding are used, and the optimal method is freely selected in consideration of material, application, strength, workability, etc.

As for the shape of the bonding surface, any shape shown in FIGS. 7(a) to 7(bo) is selected.

In Figure 7 (b), there are holes and notches on the outside, but it can still be used. However, in consideration of adhesive strength, the shapes shown in FIGS. 7(C), (D), and (E) are preferable.

Regarding adhesive application and bonding methods, if the adhesive uses a solvent, the influence of the solvent on the material will be large, so a solvent-free type is preferable.

When the hemispheres are joined as described above and a hollow sphere is completed, for example, in the case of the adhesive application joining method, the adhesive protrudes from the joint, so it is removed in the subsequent deburring process. This deburring is done using a polishing machine. In addition, a grinding method using a cutting tool is also used.

Finally, the surface of the sphere is also finished as a post-treatment, and a sandblasting method or a ramping method is employed.

Generally speaking, there is no Japanese Industrial Standard for Bing Pong balls, and the International Table Tennis Federation specifies that they are made of plastic, but the material has not yet been determined.

But the diameter of the sphere (37,7 m / m ± 0.5),
M amount of the ball (2,46 ± 0.06 g), repulsive force of the ball (dropped from 30.5 cm above the standard board 23.5 ~ 25,5
Bing pong balls were made according to the method of the present invention by using ABS resin, taking into consideration the specific gravity, film thickness, etc. of the resin, and also taking into consideration workability with adhesives. A new pin bong ball with extremely high strength against tear and tension.

Moreover, when the Bing Pong balls were observed with a polarizing plate, a very remarkable alignment phenomenon was observed.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of the mold of the present invention. FIG. 2 is an embodiment showing the method of arranging the mold of the present invention. FIG. FIG. 6 shows different embodiments of the joining device. FIGS. 7(A) and 7(E) show modified embodiments of various joining surfaces. (1) Cavity (3) Gate (4) Rotating core (6) Spindle procedure amendment (method) October 11, 1980 Director General of the Japan Patent Office Will Kagaku-dono 5 Planes 1, Incident Display 1986 Patent Application No. 100001/26
Name of Ming Method for manufacturing a medium-sized hemisphere and device No. 7 ft3
, Relationship with the case of the person making the amendment Applicant 4, Agent 〒102

Claims (2)

[Claims] (1) While rotating either or both of the injection mold consisting of a cavity or a core, resin is injected into the mold through a gate located at a position offset from the center of the mold to form a hollow hemisphere. While molding the body, the resin is compressed while rotating the mold, or after the mold rotation is stopped, the mold is further rotated in the opposite direction to create a three-layer structure in the resin I of the hollow hemisphere. A method for manufacturing a hollow hemisphere, characterized by forming a hollow hemisphere. (2) Implementation of the manufacturing method according to claim 1, wherein one or both of the molds having a gate at a position offset from the center is an injection molding mold with a rotation function. Hollow hemisphere injection molding equipment used.