JPS5917665B2 - Mold for molding rubber products - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the structure of a mold for molding rubber products. By installing a movable valve, or a structure consisting of an outer cylinder and a movable valve (hereinafter referred to as a vent unit), the gas can be smoothly exhausted out of the mold and the molded product can be prevented from flowing out. The present invention relates to a type 5 molding die for rubber products that can completely prevent the formation of unnecessary protrusions on the surface of the molded product and obtain a good molded product.

When molding rubber products such as tires, there is a space between the inner surface of the mold and the molded product, and if the product is molded without air or other gases being discharged into this space, defects may occur due to residual gas called light. It tends to be a certain type of product.

Therefore, in order to prevent this type of defect, various methods have been implemented to remove residual gas between the molded product and the mold during molding. Conventionally, this type of method consists of (1) making small holes penetrating the inside and outside of the molding die; During molding, a part of the molded material flows out through the small holes as gas is discharged, resulting in a loss of molding material.Furthermore, there is a process of mechanically cutting and removing protrusions caused by the flow of the molded material. There were drawbacks such as the need for

In addition, sometimes the small holes are blocked because the molded material is cut while still being filled in the small holes, resulting in defective products or requiring work to repair the blocked 'J-ji L'. There were flaws. ■5(2) Use the slit between the opening that penetrates the mold and the plug fixedly inserted into the opening to prevent the molded product from flowing out and discharge gas to the outside of the mold. - by using the force method (Special Publication No. 41-1956) or installing a structure in which a large number of fine wires are bundled and tightly fixed in the above opening, the gaps between the thin wires and between the object that fixes the thin wires and the thin wires are utilized. There are methods to discharge the gas inside the mold without causing the molded product to flow out (Japanese Patent Publication No. 45-5897), but all of these methods remove solids attached to the molded product and various types contained in the molded product. There was a drawback that there was a high possibility that volatile substances would adhere and cause clogging.

In the former case, the gas flowing through the gap between the opening and the plug can be expected to have the effect of self-cleaning the gap, but since the plug is a fixed type, the self-cleaning effect only by the gas passing through is low. It had drawbacks such as difficulty in long-term use. (3) An intermediate stage is provided by widening the inner surface of the opening that penetrates the mold, and this intermediate stage is made of a material that allows only gas to pass through, but not the molded product, such as sintered metal, and is breathable. Tungsten carbide products A method of embedding various ceramic materials with air permeability, various heat-resistant polymer materials with air permeability, etc., or a breathable embolus with a zigzag peripheral surface to provide air permeability between the opening and the above-mentioned opening. The gas inside the mold is discharged by the method of embedding the mold (Japanese Patent Publication No. 45-5896), but this method also allows solid matter adhering to the molded product and volatile components emitted from the molded product to adhere to the mold. As a result, the hole becomes clogged and cannot function as an exhaust hole in a relatively short period of time.

(4) There are many other cutting methods that utilize various micropores and slits, but depending on the hole diameter and slit width, the molded product may be cut while still flowing in, or solids may be attached to the molded product. All of them have the disadvantage that they become unable to function as exhaust holes within a relatively short period of time due to clogging due to adhesion of various volatile components emitted from objects and molded products. (5) Furthermore,
As a conventional method that is completely different from the above-mentioned methods, for example, British Patent No. 922788 discloses that a valve opening/closing mechanism is used to exhaust the gas between the molded product and the mold to the outside of the mold. describes a force method that prevents it from flowing out of the mold.

In this method, the fitting part between the valve and the valve seat to prevent the molded product from flowing out has a structure that is formed by surface contact between the sloped surface or flat surface of the valve and the valve seat. Moldings tend to adhere to the parts and the valve tends to malfunction within a relatively short period of time, making it difficult to withstand reliable use over a long period of time. The present invention aims to solve the above-mentioned drawbacks of the prior art, and the molded product flows out from the exhaust hole provided to exhaust the gas existing between the mold and the molded product to the outside of the mold in the molding of rubber products. This prevents the formation of unnecessary protrusions on the surface of the molded product, and also improves the performance and durability of the movable valve used for this purpose, or the vent unit consisting of the movable valve and the outer cylinder. The purpose of this invention is to provide a mold for molding rubber products.

That is, the present invention includes an exhaust hole that penetrates the mold, and a valve seat is provided in the exhaust hole with a part of the inner wall surface of the exhaust hole as a fitting edge portion, and the valve is attached to and detached from the valve seat. In addition to providing a movable valve that functions, it is also possible to ensure that the fitting part of the valve seat and the movable valve are 0.
．． 2m! A slightly wide gap is formed between the inner wall surface of the exhaust hole and the movable valve following the valve seat, and a narrow gap that does not impede ventilation is formed following this gap. The gist of the mold is a mold for molding rubber products, which is characterized by having a gap or a sliding part to prevent the movable valve from moving laterally, and also includes an exhaust hole that penetrates the mold. Inside, there is provided a vent unit consisting of an outer cylinder, a valve seat with a part of the hole in the outer cylinder as a fitting edge part, and a movable valve that is attached to and detached from the valve seat to perform a valve action. , the fitting edge of the valve seat and the movable valve should be in contact with each other with a width of 0.2 mm or less, and a slightly wider gap should be provided between the inner wall surface of the outer cylinder and the movable valve following the valve seat. A mold for molding a rubber product is characterized in that a slit or a sliding portion is provided following this gap to an extent that does not impede air permeability, thereby preventing sideways wobbling of a movable valve. This is a summary.

Note that the rubber products in the present invention include vulcanized rubber used for tires, belts, etc., thermoplastic rubbers such as SBR, polyisoprene, polyolefin, polyurethane, and polyester, or compression moldable thermoplastic rubbers. Contains plastic resin, etc.

The present invention will be further described below with reference to embodiments shown in the accompanying drawings.

FIG. 1 is a partial cross-sectional view schematically showing a state in which a tire is molded using a tire molding mold according to the present invention. In the figure, reference numeral 1 indicates a part of the mold, and inside the mold 1, a tire 2 is formed. It is formed.

A large number of exhaust holes 3 are bored in the mold 1. Inside this exhaust hole 3, a vent unit 4 consisting of an outer cylinder and a movable valve built into the outer cylinder is installed as shown below. FIG. 2 shows one embodiment of this vent unit 4, in which FIG. 2a is a front sectional view of the vent unit 4, and FIG. 2b is a sectional view taken along line AO) AA in the same figure.

The vent unit 4 consists of an outer cylinder 5 installed in the exhaust hole 3 of the mold 1, and a movable valve 6 built in the hole 5a of the outer cylinder 5 to perform a valve function. An exhaust hole 3 is provided at one end of the outer cylinder 5.
A guide taper 7 is provided to facilitate installation of the vent unit 4 inside, and the movable valve 6 is attached to the outer cylinder 5 by a caulking portion 8 at one end via a ring 9 to prevent falling off. ing.

In addition to this example, the movable valve 6 can be attached to the outer cylinder 5 by cutting a thread at the end of the movable valve 6 and screwing a nut into it, by drilling a small hole and inserting a split pin, or by drilling a small hole and inserting a split pin. Alternatively, the end portion may be bulged to be larger than the diameter of the hole 5a of the outer cylinder 5, and the movable valve 6 can move in the axial direction within the hole 5a by a maximum of about 5 mm, preferably within a range of 1 mm or less. It is desirable to be able to do so. The hole 5a of the outer cylinder 5 has a stepped structure, and a fitting edge 10 formed in the step serves as a valve seat. The movable valve 6 is engaged and disengaged to perform a valve action.

According to the invention, a somewhat wider gap 12 is provided below the fitting edge 10 of the outer cylinder 5, and below this gap 12 a narrow gap 13 with a small clearance is provided. As is clear from FIG. 3, which is an enlarged view of part a in FIG. This is to discharge the air from the inside of the hole 5a in the order of gaps 12 and slits 13, and to prevent the molded product from flowing into the back (downward) of the hole 5a.For this purpose, after discharging the air through the hole 5a, The mating edge portion 10 and the mating inclined surface 11 are in mating contact to prevent the molded product from flowing deeper (downward) from the mating contact portion in the hole 5a.

In order to achieve this purpose, the fitting contact portion between the movable valve 6 and the outer cylinder 5 does not necessarily need to be in line contact as in this embodiment, but may be in surface contact. However, preferably, as in this embodiment, a part of the inner wall surface of the hole 5a of the outer cylinder 5, which performs a valve action by fitting into contact with the movable valve 6, is formed into a sharp edge shape as a fitting edge part 10, It is desirable that this fitting edge portion 10 be edge-fitted and in line contact with the fitting inclined surface 11 of the movable valve 6, and line contact by this edge fitting is also an important feature of the present invention.

When the present inventors conducted a comparative study on the performance of the case of line contact using edge fitting and the case of surface contact according to this embodiment, the following remarkable effects were found. In this experiment, a fitting part 10a having a sharp edge shape like the fitting edge part 10 of this embodiment as shown in FIG. The fitting part 10b that has been applied and the edge part as shown in C in the same figure are
．． The performance was compared with the fitting part 10c with chamfered X2 of 4m71L, and the quality of the performance was judged by the number of times a defect called light started to appear on the molded product after 100 repeated experiments. Table 1 shows the results. The following results were obtained.

As is clear from Table 1, it was experimentally confirmed that as the contact area of the fitting portion increases, the reliability of the vent unit decreases.

In order to clarify the reason for this, we disassembled the unit after the experiment and investigated, and found that in the case of the fitting parts 10b and 10c, the rubber material or various components contained therein were deposited on the minute slopes created by the chamfering. This is thought to be because the phenomenon occurred relatively early in the experiment, making it difficult to move the movable valve 6 up and down, and impeding the ventilation of the vent unit. In contrast, the fitting portion 10a has a sharp edge shape.
In the case of , the deposition of rubber material, etc. on the edge portion did not occur in at least 100 repeated experiments, and highly reliable performance could be demonstrated. However, in reality, there is a possibility that various volatile substances contained in the molding material may be released during molding, and furthermore, a small amount may be released due to the timing deviation of the mating contact. The molding material may flow deeper (downward) than the fitting contact area, and after repeated use over a very long period of time, it may form on the inner wall surface 5b of the outer cylinder 5 and the wall surface 6a of the movable valve 6. It is not inconceivable that solids of molding material could adhere and accumulate, impairing the full functionality of the vent unit 4.

Therefore, in order to completely prevent such a phenomenon, the present inventors conducted further intensive research, and as a result, the above-mentioned It has been discovered that the life span or durability of the vent unit 4 can be significantly improved by providing a slightly wider gap 12 as shown in FIG.

During this time? 12, that is, the clearance between the wall surfaces 5b and 6a, must be within a range where the fitting contact between the fitting edge portion 10 and the fitting inclined surface 11 is formed over the entire circumference of the vent unit 4. No. As this clearance becomes larger, the horizontal wobbling, that is, the wobbling, of the movable valve 6 becomes larger, and the movable valve 6 becomes less seated when the fitting edge portion 10 and the fitting inclined surface 11 come into fitting contact. If the movable valve 6 is poorly seated, there is a high probability that the mating contact will be incomplete, resulting in moldings flowing into the gap 12 and shortening the life of the vent unit 4.
In order to eliminate such backlash of the movable valve 6, it has been found that it is effective to provide a narrow gap 13 with a small clearance in the lower blade of the gap 12.

This narrow gap 13 also serves as a passage for discharging the exhaust gas discharged through the gap 12 to the outside (downward), and therefore, its clearance depends on the ventilation capacity of the vent unit 4. Although it is determined in relation to the allowable amount of rattling of the movable valve 6, it is generally 0.01 to 0.00 in the case of a vent unit 4 with the minimum necessary size for exhaust, for example, an outer diameter of about 5 mm. It is desirable that the length be about 20 mm. When attaching the vent unit 4 to the mold 1, the vent unit 4 can be punched into the exhaust hole 3 provided in the mold 1, screwed in by cutting a screw, or mechanically or chemically bonded with adhesive, etc. There is a method or a method using a combination of these methods, but it is easy to install, does not easily fall off during molding of rubber products, and can be relatively easily removed without damaging the mold 1 when replacing with a new one. Taking this into account, it is most preferable to use a mechanical sword method.
FIG. 4 is a diagram showing a second embodiment of the vent unit 4 according to the present invention, where a is a partial front cross-sectional view of the vent unit 4, and FIG. FIG.
In this embodiment, the gap 12a is formed by two-stage machining on the movable valve 6 side, and in this respect, the outer cylinder 5
This is different from the above embodiment in which two-stage processing was performed on the surface. In some cases, both the outer cylinder 5 and the movable valve 6 may be processed in two stages to form a gap of an appropriate width. It can be determined freely while considering the width.

FIG. 5 shows a third embodiment of the vent unit 4 according to the present invention, in which FIG. 5a is a partial front sectional view of the vent unit 4, and FIG. It is. In this embodiment, the gap 12b is formed continuously around the entire circumference of the movable valve 6 as in the second embodiment, but the narrow gap 13 is omitted, and there is a space below the gap 12b that is approximately the same as the gap 12b. A suitable number of gaps 12b1 having similar widths are formed, divided into six in the illustrated example, and the remaining portion is used as the sliding portion 14 on the outer periphery 5.
slides in the axial direction without contacting the inner wall surface of the Previously, in this embodiment, ventilation with the inside of the mold was performed using the spacer 12b.
and 12b', and the sliding portion 14 effectively prevents the movable valve 6 from rattling or moving laterally. Note that the contact of the sliding portion 14 may be either a line contact or a surface contact, and in some cases may be close to a point contact.

Further, the gap 12b' and the sliding portion 14 may be formed on the side of the outer cylinder 5, or may be formed on both edges of the outer cylinder 5 and the movable valve 6. Next, the operation of the movable valve 6 will be explained.
First, a mold 1 with a vent unit 4 installed in a large number of exhaust holes 3 is filled with molding material and pressurized. The liquid is discharged out of the mold 1 through a gap 12 and a narrow gap 13 between the fitting edge 10 of the cylinder 5 and the fitting slope 11 of the movable valve 6.

Next, the movable valve 6 is pressed outward by the pressing force of the molding material, and the fitting slope 11 of the movable valve 6 is pressed against the fitting edge portion 10 of the outer cylinder 5, thereby preventing the molding material from flowing out. can be prevented. When the gas between the molding material and the mold 1 is discharged to the outside of the mold 1, if the vent unit 4 is attached to the upper part of the mold 1, the movable valve 6 is moved by its own weight. The opening between the fitting slope 11 of the movable valve 6 and the fitting edge 10 of the outer cylinder 5 is automatically opened, and the gas is supplied between the fitting slope 11 and the fitting edge 10. , can be discharged from the mold 1 through the gap 12 and the narrow gap 13.

Further, the movable valve 6 is always pressed outward by the pressing force of the molding material between the fitting inclined surface 11 and the isthmus edge portion 10 by means of a spring or the like. (Other than this case) Even when the gas is biased in the opening direction, the gas can be discharged out of the mold 1 from the gap 12 and the narrow gap 13 between the fitting slope 11 and the fitting edge 10. Of course you can.

Further, when the vent unit 4 is attached to the lower part of the mold 1, the movable valve 6 is operated to prevent the vent unit 4 from being fitted, as in the case where the vent unit 4 described above is attached to the upper part of the mold 1. It is not possible to automatically open the space between the mating inclined surface 11 and the mating edge portion 10.

However, since the fitting slope 11 of the movable valve 6 and the fitting edge 10 of the outer cylinder 5 are generally machined, the fitting slope 11 of the movable valve 6 and the fitting edge 10 of the outer cylinder 5 are caused by the weight of the movable valve 6 itself.
Even if the fitting edge portion 10 is in contact with the fitting edge portion 10 , the gas can be sufficiently discharged from the minute gap between the fitting inclined surface 11 and the fitting edge portion 10 . Next, we will discuss the effects of installing the vent unit 4 according to the present invention.
A specific explanation will be given based on an experiment conducted comparing the case where no unit is provided.

In this experiment, a mold 40 for molding a rubber plate as shown in FIG. 7 was used, and a molding material 41 was placed inside the mold 40.
A molded product 50 shown in FIG. 8 was obtained.

The mold 40 has three molding recesses 44 , 45 , 46 formed by two partition walls 42 and 43 , and an exhaust hole 47 is formed in the recess 44 on the right side in the figure. A vent unit 4 according to the present invention was installed inside. central recess 45
Only an exhaust hole 48 is formed in the left recess 46.
There were no exhaust holes in either. A molded product 50 molded with such a mold 40 will be explained with reference to FIG.
The convex portions 54, 55, and 56 are formed by the concave portions 44, 45, and 46 of the mold 40 shown in FIG. 7, respectively.

Corner portion 56 of convex portion 56 formed by concave portion 46 without exhaust hole
A defect called a light occurs due to the influence of residual gas, and a protrusion 5 formed by molding material flowing into the exhaust hole 48 occurs in the convex part 55 formed by the concave part 45.
8 appears. On the other hand, the convex part 54 formed by the concave part 44 in which the vent unit 4 is installed in the exhaust hole 47 according to the present invention has no unnecessary protrusions, and the corner part 54a does not generate light. Sharply shaped. As described above, according to the present invention, the vent unit 4 is provided with a gap 12.
By incorporating a two-stage structure consisting of a slit 13 and a vent 13,
Although it is clear that the performance and durability of the unit 4 can be improved, the present inventors also experimentally investigated the difference in the effect depending on the installation position of the gap 12 and the change in performance due to the omission of the narrow gap 13. confirmed. That is,
The vent unit shown by A in Fig. 6 is the above example! In a similar position to that shown (with gaps 12 and 13, the vent unit shown B is opposite to A with gaps 12 and 13).
In the vent unit C, the slit 13 is omitted and only the gap 12d is provided.

In this experiment, the clearance of gaps 12, 12c, and 12d was 0.5m7! L, and the clearance of the narrow gap 13 was set to 0.1 m11. The results of this experiment are shown in Table 2, and it was confirmed that the vent unit A according to the present invention had zero incidence of defects called lights, and was significantly different from those of B and C. . It was also confirmed that in case of A, not only rubber clogging but also rubber contamination was extremely reduced. In the above embodiment, a vent unit 4 consisting of an outer cylinder 5 and a movable valve 6 is prepared in advance as a movable valve mechanism, and this is installed in the exhaust hole 3 of the mold 1. , the exhaust hole 3 drilled in the molding die 1 is directly used as a valve seat without using the outer cylinder 5, that is, the finishing accuracy of the exhaust hole 3 is improved, and the valve function is achieved by this and the movable valve 6. It is clear that even if it is made to play, the same actions and effects as those described above (by the vent unit 4) can be expected.

The material for the movable valve 6 etc. may be general metal materials such as iron, brass, stainless steel, reinforced plastics such as nylon fluorine resin, polyphenylene sulfide, ceramics, etc., but depending on the processing surface, durability, etc. Considering this, stainless steel is preferable.

Also, an outer cylinder 5, a movable valve 6, and an exhaust hole 3 into which it is inserted.
The cross-sectional shape of the cross-sectional shape is not only circular, but also various polygons, oval shapes, etc., but from the viewpoint of processing, a circular shape is preferable. As explained above, according to the present invention, the following excellent effects can be synergistically achieved.

(1) During molding of rubber products, the gas between the mold and the molded product can be easily and smoothly discharged any number of times, and the durability of the vent unit or movable valve is significantly improved.

(2) Furthermore, there is no formation of defects called lights or unnecessary protrusions due to residual gas, and the beauty of the molded product's appearance is not impaired.

(3) Since unnecessary protrusions are not formed, the time and labor required for cutting and removing protrusions as in the conventional method can be omitted.

(4) Since the movable valve is operated within the exhaust hole, the hole is self-cleaned and does not become clogged.

(5) No molding material. Since wasteful outflow is prevented, it is possible to save resources.

(6) Especially when adopting the vent unit type,
It is extremely advantageous because it can be installed and used with a slight modification of the existing exhaust hole of a conventional molding die.

(7) The inner wall surface of the exhaust hole or a part of the outer cylinder fitted to the inner wall surface is used as a valve seat with a fitting edge portion, and a movable valve that is attached to and detached from the valve seat to perform a valve action is provided; Since the fitting edge of the valve seat and the movable valve are brought into contact with a width of 0.2U or less, it is possible to more reliably prevent the molding material from flowing out of the exhaust hole, thereby preventing the generation of light. It can be used repeatedly without any problems.

[Brief explanation of drawings]

FIG. 1 is a partial sectional view of a tire molding die according to the present invention;
FIG. 2a is a partial front cross-sectional view showing an example of the vent unit according to the present invention, and FIG. 2b is a cross-sectional view taken along the line A-A.
3 is an enlarged sectional view of part a in FIG. 1, FIG. 4a is a partial front sectional view showing another embodiment of the vent unit according to the present invention, and FIG. 5a is a partial front sectional view showing still another embodiment of the vent unit according to the present invention, FIG. 5b is a sectional view taken along the line C--C, and FIG. 6 is a comparison of various vent units. Partial front sectional view showing an example,
Fig. 7 is an assembled cross-sectional view of an example of a mold for molding a rubber plate, Fig. 8 is a cross-sectional view of a rubber plate molded with the mold shown in Fig. 7, and Fig. 9 shows structural examples of various vent units. FIG. 1... Tire molding mold, 2... Tire, 3... Exhaust hole, 4... Vent unit, 5... Outer cylinder, 3a... Hole of outer cylinder, 6... Movable valve, 10... Fitting edge portion, 11... Fitting slope, 12 ,12a,1
2b, 12c, 12d...Gap, 13...
··slit.

Claims (1)

[Claims] 1. An exhaust hole passing through the mold is provided, and in this exhaust hole,
A part of the inner wall surface of the exhaust hole is a valve seat with a fitting edge, and a movable valve that is attached to and detached from the valve seat to perform a valve action is provided, and the fitting edge of the valve seat and the movable valve are provided. contact with a width of 0.2 mm or less, and form a slightly wide gap between the inner wall surface of the exhaust hole and the movable valve following the valve seat,
A mold for molding a rubber product, characterized in that a slit or a sliding portion is provided following this gap to an extent that does not impede air permeability, thereby preventing sideways movement of the movable valve. 2 Equipped with an exhaust hole that penetrates the mold, and inside this exhaust hole,
A vent unit is provided, which includes an outer cylinder, a valve seat with a part of a hole in the outer cylinder as a fitting edge, and a movable valve that is attached to and detached from the valve seat to perform a valve action. The fitting edge portion of and the movable valve are brought into contact with a width of 0.2 mm or less, and a slightly wide gap is formed between the inner wall surface of the outer cylinder and the movable valve following the valve seat, and A mold for molding a rubber product, characterized in that a slit or a sliding portion is provided following this gap to an extent that does not impede air permeability, thereby preventing sideways movement of the movable valve.