JPH06238676A - Rubber core member - Google Patents

Abstract

PURPOSE:To facilitate the pulling-out of a core member at the time of mold opening by forming at least a part coming into contact with a molded product of the core member arranged in a mold from a rubber material at the time of the molding of a resin product having a hollow part or a through-hole. CONSTITUTION:At the time of the molding of a pipe-shaped article 2, a rubber core member 1 wholly composed of a rubber material is used. Or, the core member 1 may be constituted by attaching a rubber sleeve to a metal core material. In the case of the core member used in the molding of a resin product having an undercut part, for examaple, only a part 8A becoming a hooking part with respect to the product is made of rubber and the other part 8B can be formed from a metal. When at least the part coming into contact with a molded product is partially made of a rubber material as mentioned above, the core member can be easily pulled out only by usual mold opening and closing operation even with respect to a long pipe-shaped article having uniform wall thickness or a product having an undercut part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber core member,
In particular, the present invention relates to a core member such as a core or a core pin arranged in a molding die when molding a resin product having a hollow portion or a through hole, which is a rubber core member that can be easily pulled out when the die is opened.

[0002]

2. Description of the Related Art When molding a resin product having a hollow portion or a through hole, a protruding portion called a core or a core pin is provided in a molding die (mold), and the mold is filled with resin. It is solidified to form a hollow portion and a through hole.

Conventionally, such a core or core pin is made of metal like the mold.

By the way, since the resin shrinks in the mold when it solidifies, the product molded into the core and core pins bites, making it difficult to remove (remove) from the mold or take it out. Often becomes. Then, if the product is taken out forcibly, the product may be scratched or, in a significant case, the product may be damaged.

Therefore, in the past, in order to alleviate the bite of the product on the core or core pin and enable smooth demolding and removal, the core or core pin is generally expanded in the direction of removal. A taper to make a diameter is performed. This is called a draft taper, and the taper angle is usually 1 to 2 °.

The most serious problem of such biting on the core or core pin due to the shrinkage of the resin is a hollow elongated product, a so-called pipe-shaped product.

That is, since the length in the longitudinal direction of the core pin used for molding the pipe-shaped product is extremely long, a large force is required to pull out the core pin at the time of demolding, and the solidification of the resin is insufficient. If so, buckling may occur when the core pin is pulled out, and the product may be wrinkled or cracked.

In this case, as described above, the removal of the mold is facilitated by providing the core pin with a taper, but the middle hole of the obtained product is also tapered, and the pipe has a uniform wall thickness. It is not suitable for use as a general-purpose pipe.

For example, when a core taper is formed with a taper of 1 ° to form a pipe having a length of 1 m, the difference in wall thickness between the end faces of the obtained pipe is as large as 17.5 mm, which cannot be put to practical use. .

Therefore, a method has been proposed in which a collapsible core is used as a core pin in order to eliminate the taper of the core pin and form a pipe-shaped product having a constant wall thickness.

The collapsible core is provided with a mechanism for reducing the cross-sectional area of the core by utilizing the opening / closing operation of the mold, and the core can be released from the product without difficulty. Moreover, its mechanism is very simple and can be used just like an ordinary core pin, so it has been widely used in the past for molding products such as cap-shaped lids, pipe-shaped objects, sleeves and ring-shaped objects. There is.

However, due to the structure of the collapsible core, there is a limit to the product size that can be molded, and the length is about 50 mm and the diameter is about 80 mm. Therefore, it is usually impossible to produce a pipe-shaped product having a length of several tens of cm to 1 m or more that can be used as a high-strength structural member, and such a long pipe-shaped product is generally extruded. It is currently manufactured in.

Another problem in mold-molding a resin product having a hollow portion or a through-hole portion and releasing the same is that there is an undercut. That is, if there is a protrusion on the side surface of the product or if there is a recess in the product with respect to the direction in which the product is taken out, this part will be caught by the mold and cannot be taken out. In this way, when the product is taken out of the mold, the part that becomes caught in the opening / closing direction of the mold is called an undercut, and for example, holes, grooves, letters on the side of the box-shaped product, ribs on the inside, Others are cap screws.

In the case of demolding a product having such an undercut, the following measures have hitherto been taken.

First, as a first measure, there is a method using the above-mentioned collapsible core. Since this method has a simple mechanism and good productivity, it is most suitable for molding products with hollow parts and holes that have undercuts. Among them, cylindrical products with screws, such as caps, rings and sleeve products. Is extremely effective for However, as mentioned above, there is a limit to the core size of about 50 mm in length and about 80 mm in diameter, and the maximum amount of the tip of the core that directly affects the releasability of the product is about 4 mm on each side. Therefore, there is a drawback that the protruding width or the retracting width of the undercut portion is also limited.

As a second measure, there is a method in which the mold has a slide core structure. In this method, the mold part of the undercut part is used as a slide core, and this core is slid in advance when releasing from the mold so that the undercut part does not get caught in the mold when taking out the product. It has a type structure. As a method of moving this slide core, there are a method of moving it in conjunction with opening and closing of the mold using an angular pin or an angular cam, and a method of moving it separately from the opening and closing of the mold using a hydraulic cylinder or pneumatic cylinder separately installed. There is. The former method is used when the slide core is provided on the movable side of the mold, and the latter method is used when the slide core is provided on the fixed side. By using such a slide core, there are no dimensional restrictions such as the length and diameter of the core, and above all, the protruding width and the withdrawal width of the undercut part, unlike the collapsible core. However, there is an advantage that the mold can be removed from a complicated product. However,
On the contrary to the above advantages, the mold structure becomes complicated and the attached cylinder device is required, which causes the mold to become larger and heavier, resulting in poor workability during mold replacement and the need for regular maintenance. Then, a problem such as an increase in cost occurs.

[0017]

As described above, the conventional molding of resin products using cores or core pins has the following problems when the products are demolded.

Since the resin shrinks when it solidifies, the product sticks to the core and core pins, making it very difficult to pull out the core and core pins, and it is impossible to demold. This problem is particularly noticeable in the case of a long pipe-shaped product, and if the core pin is forcibly pulled out at the time of demolding, wrinkles or cracks will occur due to buckling.

In order to solve the problem of (1), if the core pin is formed with a taper, the core pin can be easily drawn out, but on the other hand, the hollow part has a tapered pipe shape with an uneven wall thickness. I don't get.

In contrast to the above, if a collapsible core is used by giving priority to the extraction of the core in order to obtain a pipe having a uniform wall thickness, dimensional constraints are added to the pipe shape, for example, a length of about 50 mm, The upper limit is about 80 mm in diameter.

When the undercut portion is processed on the core or core pin side, the protrusion or recess of the undercut portion may be caught in the mold by only opening and closing the mold, and it is physically impossible to take out the product. It will be possible.

In order to solve the above problem, there is a method of using a collapsible core or a method of forming a mold into a slide core structure. However, the collapsible core has dimensional restrictions in length and diameter as described above, Since the amount of narrowing is also limited, the protruding width and the retracting width are also limited due to the undercut portion, and as a result, the product that can be molded is also limited to within that range. On the other hand, if the slide core structure is adopted, there are no restrictions on the product shape,
The mold structure becomes complicated and the attached cylinder device is also required, resulting in larger and heavier molds, poor workability during mold replacement, the need for regular maintenance, and increased costs. There is a problem such as.

The present invention solves the above-mentioned problems caused by the conventional metal core or core pin, and produces a product having a long pipe shape of uniform thickness or an undercut, a special core mechanism or a die structure. It is an object of the present invention to provide a rubber core member capable of promptly pulling out a core and taking out a product by simply opening and closing a mold without requiring the above.

[0024]

The present invention is characterized in that, in a core member arranged in a molding die, at least a part of a portion in contact with a molded product is made of a rubber material.

In the present specification, "core member"
Includes all members such as the cores and core pins described above, which are arranged in the mold for forming hollow portions, through holes, and undercut portions of the product.

Further, in the present specification, the "rubber material" causes a considerably large deformation at room temperature with a small stress, and when the stress is released, the deformation is rapidly and almost completely restored to the original shape. It refers to a polymer substance that can be used.

Basic rubber materials suitable for the rubber core member of the present invention include natural rubber (NR) and synthetic rubber. Of these, specific examples of the synthetic rubber include isoprene rubber (IR), butadiene rubber (BR), 1,2-polybutadiene rubber (1,2-BR), styrene-butadiene rubber (SBR), chloroprene rubber (CR), Nitrile rubber (NBR), butyl rubber (IIR), ethylene-propylene rubber (EPM), chlorosulfonated polyethylene (CSM), acrylic rubber (ACM), epichlorohydrin rubber (CO), silicone rubber (Q), fluorine rubber (FKM) , Urethane rubber (U), etc. Of these, NR, IR, BR, 1,2-BR, SBR, C
R, NBR, IIR, EPM, CSM, ACM, Q, F
Particularly preferred are KM, U and the like. These rubbers can be used alone or as a mixture of two or more kinds. In addition, various reinforcing agents and fillers are added for the purpose of improving properties such as heat resistance, wear resistance, thermal expansion, flame retardancy, chemical resistance, mold release property, processability, fluidity, and adhesion to metal. It is also possible to mix required amounts of agents, anti-aging agents, crosslinking agents, oils, plasticizers, accelerators, oligomers and the like.

In particular, in the present invention, it is preferable to use a rubber material satisfying the following characteristics in consideration of the withdrawal performance and strength as the core member.

Hardness: 40-80 Tensile strength: 150 kg / cm ² or more Elongation: 200-600% If the hardness of the rubber material used in the present invention is less than 40, sufficient rigidity as a core member cannot be obtained, If it exceeds 80, sufficient deformation cannot be obtained, and there is a possibility that defects such as scratching the product at the time of pulling out may occur. Also, the tensile strength is 150
If it is less than kg / cm ² , the strength is insufficient with respect to the stress at the time of drawing, and drawing may be difficult. Furthermore,
If the elongation is less than 200%, sufficient deformation of the core member cannot be obtained during drawing, and if it exceeds 600%, the rigidity of the core member is insufficient.

The rubber core member of the present invention may be entirely composed of such a rubber material, or may be composed of a combination of a rubber material and a metal material. For example, only the surface layer in contact with the molded product may be made of a rubber material, and the central portion may be made of a metal material. Further, a part of the portion contacting the molded product or only the surface layer portion of the part may be made of a rubber material, and the other portions may be made of a metal material.

[0031]

In the rubber core member of the present invention, at least a part of the portion in contact with the molded product is made of a rubber material. Even for long pipe shaped products and products with undercuts, it is possible to easily pull out the core member only by normal mold opening and closing operation without requiring any special core mechanism or mold structure. To be done.

That is, when a pipe-shaped product having a uniform thickness is molded and released from the mold, the rubber core member of the present invention is simply pulled, and the cross-sectional area of the rubber core member is reduced by Poisson contraction. The interface between the product and the rubber core member is separated, and the core member can be easily pulled out.

Further, even in the case of a product having an undercut, the rubber core of the present invention can provide the softness of the rubber material with respect to the protrusion and the withdrawal which become a catching portion in the pulling direction of the core member. The core member can be quickly pulled out due to its flexibility and large deformability.

By fully utilizing the characteristics of rubber materials such as flexibility, large deformation performance, and incompressibility that metal materials do not have, the long pipes that cannot be demolded by only opening and closing the dies have been used. It is possible to easily take out a shaped product or a product having an undercut from the mold. Moreover, according to the rubber core member of the present invention, it is possible to provide a die which is excellent in mass productivity, has a simple structure, and is low in cost.

[0035]

Embodiments of the rubber core member of the present invention will be described in detail below with reference to the drawings.

1 to 8 are sectional views showing an embodiment of the rubber core member of the present invention. 1 to 8, A and B indicate molds.

FIGS. 1 and 2 show a core member 1 used for molding a pipe-shaped product 2, the rubber core member 1 being entirely made of a rubber material.

As described above, the advantage in the case where the entire core member is made of only the rubber material is that the deformation amount of the core member can be made large and the core member can be easily pulled out. That is, when the core member 1 is pulled out from the pipe-shaped product 2 shown in FIG. 1, when the rubber core member 1 is pulled along with the opening of the molds A and B as shown in FIG. Even if the shape 2 bites the core member 1, the cross-sectional shrinkage of the rubber is much larger, so the interfaces 2A, 1A between the resin (pipe shape 2) and the core member 1 are easily separated, and the core The member 1 can be easily pulled out.

FIG. 3 shows a rubber / metal composite core member 3 which is also a core member used for molding a pipe-shaped product.

That is, the core member 3 of this embodiment is constructed by attaching a rubber sleeve 3B to a metal core material 3A.

Although the rubber core member 1 made of only the rubber material shown in FIGS. 1 and 2 can be largely deformed,
Since it has low rigidity, it has a weak point that it is easily deformed by external force. On the other hand, the rubber / metal composite core member 3 shown in FIG. 3 can be a high-performance core having both high rigidity due to the metal core material 3A and large deformability due to the rubber sleeve 3B. With such a core member 3, a product having high dimensional accuracy can be molded without being bent or deformed even with a high resin pressure generated at the time of molding due to its high rigidity.

Such a rubber / metal composite core 3 member is
In manufacturing the same, a rubber sleeve 3B and a metal core material 3
If A and A are firmly bonded and integrated, they can be handled in the same manner as a conventional metal core. On the other hand, by putting a lubricant such as oil in the interface between the rubber sleeve 3B and the metal core material 3A so that they can be easily separated from each other, when the mold is opened, the metal core is first Only the material 3A is pulled out, the rubber sleeve 3B is left as it is on the product side, and then, as a second step, the rubber sleeve 3B is pulled out from the inside of the product, so that it can be easily released from the mold. As described above, first, when only the metal core material 3A is pulled out, the rubber sleeve 3B is made of only a rubber material and is in a hollow state, so that the deformation at the time of pulling out the rubber sleeve 3B in the second stage is prevented. Noticeably bigger,
It can be pulled out from the product with very little force. Therefore,
Such a two-step drawing method using a rubber / metal composite core member is effective for a material having extremely large shrinkage or a pipe having an undercut on the inner surface.

4 and 5 show core members used for molding resin products 4 and 5 having undercuts, and rubber core members 6 and 7 made entirely of a rubber material. .

When these rubber core members 6 and 7 are pulled in the mold opening direction indicated by the arrow at the same time when the molds are opened, the rubber materials of the portions 6A and 7A serving as the protrusions of the core members 6 and 7 are largely deformed. Since the parts 4A and 5A which become the catches of the products 4 and 5 are easily overcome, the rubber core members 6 and 7 can be smoothly pulled out.

FIGS. 6 to 8 show a rubber / metal composite core member similarly used for molding a resin product having an undercut.

That is, the rubber / metal composite core member 8 of FIG.
In the case where the core is pulled out, only the portion 8A that is caught by the product is made of a rubber material, and the other portion 8B is made of metal. With such a rubber / metal composite core member 8, when the core member is pulled out, only a portion 8A made of a rubber material, which becomes a catch, is largely deformed,
The core member can be easily pulled out because it goes over the convex portion of the product that becomes a catch.

In FIG. 7, only the undercut portion 9A of the surface layer of this catching portion is made of a rubber material, and the other portion 9B is made of metal.

In such a rubber / metal composite core member 9, the surface layer portion 9A made of a rubber material is replaced by the core portion 9 made of a metal.
With respect to B, the rubber / metal composite core member 9 has a surface layer portion 9A left on the product side, and only the core portion 9B is pulled out together with the mold opening.
The core member can be easily pulled out by peeling off the surface layer portion 9A from the product.

Then, when the next molding is performed, the surface layer portion 9A made of a rubber material is replaced with a metal core portion 9B by a robot or the like.
It is possible to easily carry out automatic molding continuously by attaching to.

At this time, as shown in FIG. 8, the metal core portion 10B of the rubber / metal composite core member 10 is provided with a positioning groove or hole 10a so that the surface layer portion 10A made of a rubber material can be easily formed. Will be installed in the correct position.

Of the rubber core members of the present invention, in order to manufacture a rubber core member composed only of a rubber material, the rubber material is poured into a mold in which a portion made of the rubber material is carved, and a conventional method is used. It may be heated, pressurized and vulcanized in accordance with the procedure.
A rubber / metal composite core member is manufactured by inserting a metal core into a rubber casting mold, vulcanizing and integrating with the rubber, and simultaneously adhering and shaping the rubber and the metal. Alternatively, the rubber material portion and the metal portion may be separately formed in a predetermined shape in advance, and then integrated.

As a method of attaching such a core member to the mold body, in the case of a rubber core member made of only a rubber material, vulcanization adhesion or a method of using an ordinary rubber / metal adhesive, bolts and rivets are used. Mechanical fastening methods such as can be used together. On the other hand, in the case of a rubber / metal composite core member in which the mounting surfaces are metals, the fastening method generally used for metal molds, such as bolts, can be directly adopted.

[0053]

As described above in detail, with the rubber core member of the present invention, the core member can be easily pulled out at the time of demolding, and it is impossible to mold with the conventional metal core. It becomes possible to easily form a long pipe-shaped product. In addition, even if the product has an undercut, the core can be easily pulled out only by opening and closing the mold without adding a slide core mechanism to the mold, and the product can be taken out.

As described above, by using the rubber core member of the present invention, the performance of the conventional mold can be improved, the structure of the mold can be simplified, the weight can be reduced, and the maintenance can be made free, and the cost of the mold can be reduced. It is valid.

The rubber core member of the present invention can be effectively applied to all molds such as compression molding molds and injection molding molds for shaping the product shape by the molds.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a rubber core member of the present invention.

FIG. 2 is a cross-sectional view showing a state when the mold of the rubber core member shown in FIG. 1 is opened.

FIG. 3 is a sectional view showing another embodiment of the rubber core member of the present invention.

FIG. 4 is a sectional view showing another embodiment of the rubber core member of the present invention.

FIG. 5 is a cross-sectional view showing another embodiment of the rubber core member of the present invention.

FIG. 6 is a sectional view showing another embodiment of the rubber core member of the present invention.

FIG. 7 is a cross-sectional view showing another embodiment of the rubber core member of the present invention.

FIG. 8 is a cross-sectional view showing another embodiment of the rubber core member of the present invention.

[Explanation of symbols]

 A, B Mold 1,6,7 Rubber core member 2 Pipe shaped object 3,8,9,10 Rubber / metal composite core member 3A Metal core material 3B Rubber sleeve 4,5 Resin product

Claims (1)

[Claims] 1. A rubber core member, characterized in that, in a core member arranged in a molding die, at least a part of a portion in contact with a molded product is made of a rubber material.