JP3308843B2 - Press molding method for rubber products - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for press-molding rubber products such as small sealing materials and packing materials.

[0002]

2. Description of the Related Art A conventional O-ring press forming method will be described. For example, as shown in FIGS. 4 and 5, a cavity 2 as a ring-shaped concave portion is formed in 8 columns × 10 rows in the vertical and horizontal directions on the mold surface of the lower mold 1 used in this press molding method. A concave rubber relief groove 4 is formed on the peripheral edge of the molding die surface so as to surround the entire area where these cavities 2 are formed. Also, this mold surface
It is divided into four rectangular sections 3 each including two rows of cavities 2 of 8 columns × 10 rows, and a concave rubber escape groove 5 is formed between the sections 3. That is, each section 3 is surrounded by the rubber relief groove 4 or the rubber relief groove 5 around the rectangular mold surface on which the two rows of cavities 2 are formed.

As shown in FIG. 6, a molding die surface of an upper die 6 is located at a position corresponding to each cavity 2 of the lower die 1.
Each cavity 7 is formed as a ring-shaped concave portion, and when these cavities 2 and 7 are put together, a donut-shaped void conforming to the shape of the O-ring is formed. The upper mold 6 shown here does not have a rubber escape groove.

[0004] A single rubber sheet 8 made of raw rubber is placed on the surface of the lower die 1 as shown by a one-dot chain line in Figs. The rubber sheet 8 has a substantially square shape, and is placed so as to cover all the four sections 3 in which the cavities 2 of 8 columns × 10 rows are formed. It will be arranged on the groove 4.
As shown in FIG. 6, the upper mold 6 is disposed above the lower mold 1 on which the rubber sheet 8 is placed, with the mold surface in which the cavity 7 is formed facing downward. By pressing the lower mold 1 and the upper mold 6, the rubber sheet 8 is pressed.
Is filled into the cavities 2 and 7 and press-molded, and the excess rubber sheet 8 overflowing from the cavities 2 and 7 is pressed between the upper and lower molds 1 and 6 to form a peripheral side. And push it into the rubber escape grooves 4 and 5.

Since the dies 1 and 6 are pre-heated, the raw rubber of the rubber sheet 8 is vulcanized and cured during press molding. Accordingly, the rubber sheet 8 filled in each of the cavities 2 and 7 is cured in the donut-shaped gap to form an O-ring. When vulcanization is further promoted in this state, the upper mold 6 is removed upward, and the O-rings hardened in the cavities 2 and 7 are taken out. Further, since thin film-like burrs cured between the molding surfaces of the lower die 1 and the upper die 6 adhere to these O-rings, the burrs are removed in a later step.

By the way, the molding die surface of the lower mold 1 is divided into the sections 3 and the rubber escaping grooves 5 are formed between them. The excessive rubber sheet 8 overflowing from the cavity 2 must be moved while being pressed for a long distance until reaching the rubber escape groove 4 on the peripheral edge of the molding die surface, so that only a strong pressing force is required. The reason is that the raw rubber is vulcanized by heating during the long-distance movement and hardens without reaching the rubber escape groove 4. When each section 3 includes three or more rows of the cavities 2, the excess rubber sheet 8 overflowing from the cavities 2 in both rows is pressed and can be immediately released to the side rubber escape grooves 4 and 5. However, since the extra rubber sheet 8 overflowing from the cavities 2 in the center row needs to move a certain distance before reaching the side rubber escape grooves 4 and 5, the rubber sheet 8
Pressing conditions such as sheet thickness and pressurizing force for proper filling and eliminating pressure of overflowing excess rubber sheet 8 greatly differ depending on the row of cavities 2 in the same section 3, and more than necessary. The rubber sheet 8 must be thickened and the pressing force must be increased. However, if only one row of cavities 2 is included in each section 3, rubber escape grooves 5 must be formed for each row, and the number of cavities 2 that can be formed on the mold surface of the lower mold 1 is reduced. And the productivity decreases. Therefore, conventionally, each section 3 has two cavities 2.
Partitioned to include columns.

[0007]

However, in the conventional rubber product press molding method, as described above, one rubber sheet 8 is placed on the molding die surface of the lower die 1 and all the sections 3 are formed.
Was covered. That is, since the lower mold 1 is always heated, if press molding is not performed immediately after the rubber sheet 8 is placed, the raw rubber is vulcanized and cured in a sheet form. In addition, conventionally, the rubber sheet 8 is placed on the molding surface of the lower mold 1 by a manual operation or a transfer device having a simple mechanism, and therefore, only one rubber sheet 8 can be placed at a time. was there.

For this reason, even when the rubber escape groove 5 is formed between the sections 3 as in the prior art, the rubber sheets 8 have to be placed more than necessary in each section 3, so that the cavity There is a problem that the amount of the excess rubber sheet 8 overflowing from 2 becomes too large and a strong pressing force is required, and the press device is large and expensive. Also, if the amount of the excess rubber sheet 8 is too large, the burrs adhered to the O-ring may not be sufficiently removed during press molding, and a large amount of rubber sheet 8 may be pressed during this press molding. There is also a problem that the edge portions of the dies 1 and 6 are worn down when they are instantaneously moved to the side, thereby shortening the life. further,
Since the extra rubber sheet 8 is wasted material, the material yield is reduced, and furthermore, in order to remove this large amount of excess rubber sheet 8 by pressing without excess or shortage, a sheet of the rubber sheet 8 of about 0.5 mm is used. There is also a problem that it is necessary to precisely control the thickness with an accuracy of about 0.01 mm.

The above problem is not limited to the O-ring press molding method, but is common to press molding methods for producing a large number of rubber products by press-molding a rubber sheet.

[0010] The present invention has been made in view of the above circumstances, and a plurality of rubber sheets, which are slightly smaller than the section, are placed on each section on the mold surface of the mold, and thus the press is performed. An object of the present invention is to provide a method for press-molding a rubber product, which can improve the material yield by reducing the pressing force at the time of molding.

[0011]

That is, in order to solve the above-mentioned problems, the present invention provides press molding by placing and pressing a rubber sheet on a molding die surface of a mold provided with a number of cavities. In the method of press-molding a rubber product, the rubber escape groove surrounds the entire molding area of the mold surface of the mold, and further divides the mold surface into a plurality of sections each including a plurality of cavities. Each time, a rubber sheet slightly smaller than the section shape is placed and pressed.

According to the means of the present invention, instead of covering the entire mold surface of the mold with one rubber sheet, a rubber sheet of a slightly smaller size is placed in each section, so that the inside of each section and The rubber sheet is not unnecessarily placed between the sections, and a rubber sheet having an appropriate size can be placed. Therefore, the amount of excess rubber sheet overflowing from each cavity during press molding is reduced, so that a pressing force for pressing and eliminating the rubber sheet can be reduced. Also, if the same pressing force as in the related art is applied, more cavities can be formed in the mold surface of the mold. In addition, the thickness of the burrs attached to the rubber product is reduced, and the wear on the edge of the mold is reduced. Further, since the waste of the material due to the extra rubber sheet is reduced, the material yield is increased, and it is not necessary to precisely control the sheet thickness in order to press and remove the extra rubber sheet without excess or shortage.

Since a plurality of rubber sheets are preferably placed at the same time, it is convenient to use a transport device capable of simultaneously transporting the plurality of rubber sheets. The cavity is usually formed in both upper and lower molds, but may be formed in only one of the molds depending on the shape of the rubber product. When the cavity is formed only in the upper mold, the rubber sheet may be placed in each section on the lower mold corresponding to each section divided based on the cavity of the upper mold. Further, a kerf for deburring may be formed around each cavity.

Further, the above-mentioned section has two cavities.
It is divided so as to include rows, and a rectangular rubber sheet slightly smaller than the section is placed on each section and pressed.

According to the means, by dividing the cavity every two rows, the division can be efficiently divided. That is, if the cavities are divided in each row, the number of rubber sheets placed on the mold almost simultaneously becomes too large. This is because the pressing conditions for eliminating the pressure are greatly different between the rows at both ends and the row at the center, so that it is necessary to unnecessarily thicken the rubber sheet and increase the pressing force. Also, simply cut a long rubber sheet material of a certain width at a predetermined pitch in the longitudinal direction,
A strip-shaped rubber sheet placed on each section can be easily obtained.

Further, a concave rubber escape groove is formed between each section on the mold surface of the mold.

According to the means, a rubber escape groove for storing an extra rubber sheet is formed between the sections, so that the pressing conditions of the section at the end of the mold surface and the center section are made uniform. can do. The rubber escape groove may be formed in at least one of the upper and lower molds.

[0018]

Embodiments of the present invention will be described below with reference to the drawings.

1 to 3 show an embodiment of the present invention. FIG. 1 is a perspective view of a lower mold, FIG. 2 is a plan view of the lower mold, and FIG. It is a longitudinal cross-sectional view which shows the mode at the time of press-molding a rubber sheet. Components having the same functions as those of the conventional example shown in FIGS. 4 to 6 are denoted by the same reference numerals.

In this embodiment, a method for press-forming an O-ring will be described. As shown in FIGS. 1 and 2, the lower mold 1 used in this press molding method is the same as the conventional example shown in FIGS. That is, the mold surface is
The cavities 2 are formed vertically and horizontally in 8 columns × 10 rows, and are divided into four rectangular sections 3 so as to include these cavities 2 in two columns each. In addition, these four sections 3
A rubber escape groove 4 is formed around the periphery of each of them, and a rubber escape groove 5 is also formed between each of the sections 3.
However, in order to simplify the drawing, cavity 2
Is limited to 80 (= 8 × 10) locations, but in an actual mold, more cavities 2 are formed in order to press-mold up to about 400 O-rings at a time. Accordingly, the number of sections of the section 3 including the cavities 2 in two rows can be further increased. In the present invention, the number of the cavities 2 and the number of the sections 3 are not limited.

As shown in FIG. 3, the upper mold 6 used in the present embodiment is the same as the conventional mold shown in FIG. That is, the lower mold 1 is provided on the molding surface of the upper mold 6.
Cavities 7 are formed at positions corresponding to the respective cavities 2, but no rubber escape groove is formed.

In addition, around the vicinity of each of the cavities 2 and 7 formed on the molding surfaces of the lower mold 1 and the upper mold 6,
Actually, a notch not shown is formed. The kerf is a concave rubber reservoir having a width of about 1 mm and a depth of about 1 mm or less.
By forming burrs having a thickness of about several tens of micrometers between the burrs 2 and 7, the burrs can be easily removed in a later step.

On the molding surface of the lower mold 1, four rubber sheets 8 are placed as shown by a chain line in FIGS. Each rubber sheet 8 is a strip-shaped raw rubber sheet whose long side and short side are slightly shorter than each rectangular section 3, and is placed in each section 3. At this time, the rubber sheet 8 is placed so as to completely cover the two rows of cavities 2 in the section 3 (and the kerfs around each cavity 2). Further, the rubber sheet 8 is placed so that a gap of approximately the same width is opened between each of the four sides of the rubber sheet 8 and each of the four sides of the section 3. Therefore, these rubber sheets 8
Not only does it not have to cover the rubber escape grooves 4 and 5 but also the mold surface in each section 3 does not need to be completely covered, so that a rubber sheet 8 of an appropriate size can be placed. Section 3
When the number of sections is not four, the number of rubber sheets 8 to be placed also increases or decreases according to the number of sections. In addition, mold 1,
Since the rubber sheets 6 are pre-heated, unless these rubber sheets 8 are placed almost simultaneously and immediately pressed, the vulcanization and curing are started with the previously placed rubber sheets 8 remaining sheet-like. There is a fear. For this reason, it is convenient to use a transport device that can transport a plurality of rubber sheets 8 simultaneously.

As shown in FIG. 3, the upper mold 6 has a lower mold 1 on which a rubber sheet 8 is placed with the mold surface facing downward.
Is arranged above. Then, by pressing the lower mold 1 and the upper mold 6, the rubber sheet 8 of each section 3 is filled in each cavity 2, 7 and press-molded, and overflows from these cavities 2, 7. An extra rubber sheet 8 is pressed between the upper and lower mold surfaces of the molds 1 and 6 to escape to the peripheral side and is pushed into the rubber escape grooves 4 and 5.

The molds 1 and 6 are preliminarily heated at 165 ° C.
Since the raw rubber is heated to such a degree, the raw rubber of the rubber sheet 8 is vulcanized and hardened during press molding. Accordingly, the rubber sheet 8 filled in each of the cavities 2 and 7 is cured in the donut-shaped gap to form an O-ring. And 8 in this state
After pressing is continued for about a minute to accelerate vulcanization, the upper mold 6 is removed upward, and the O
The rings are taken out, and burrs of each O-ring are removed in a later step.

According to the above-mentioned press molding method, rather than placing one rubber sheet 8 on the lower mold 1 and covering the entire surface of the molding die, each of the four sections 3 has a slightly smaller size rubber. The sheet 8 is placed. Therefore, on the mold surface of each section 3, the rubber sheet 8 is not unnecessarily placed on the peripheral portion, so that excess rubber which overflows from each cavity 2 and is eliminated by pressing during press molding is eliminated. Sheet 8
And the press molding can be performed with a small pressing force. When a large pressing force is applied as in the conventional case, the number of cavities 2 and 7 formed in the dies 1 and 6 can be increased to, for example, about 600 places, and the O-ring can be manufactured by one press molding. Can be increased to increase the productivity.

Moreover, since the amount of the extra rubber sheet 8 is reduced, the amount of the rubber sheet 8 left between the upper and lower molds 1 and 6 and forming burrs is also reduced, and the thickness of the burrs is reduced. It becomes thin and easy to remove. Further, since the amount of the extra rubber sheet 8 is reduced, the amount of the rubber sheet 8 which is pressed at the time of press molding and instantaneously moves to the side is also reduced.
Wear of the edges of the dies 1 and 6 due to the movement of the rubber sheet 8 is reduced, and the life of the dies 1 and 6 can be extended.

Further, by reducing the amount of the extra rubber sheet 8, for example, the material yield which has conventionally been only about 15 to 20% can be improved to about 50%. Further, it is not necessary to precisely control the thickness of the sheet in order to remove the excess rubber sheet 8 by pressing without excess or shortage.

In the above embodiment, the upper and lower dies 1,
Although the cavities 2 and 7 are formed in the lower mold 6, the cavity 2 or the cavity 7 may be formed only in one of the lower mold 1 and the upper mold 6. Further, although the rubber escape grooves 4 and 5 are formed only in the lower mold 1, the same rubber escape groove can be formed in the upper mold 6, or the rubber escape groove can be formed only in the upper mold 6. . In addition, since the excess rubber sheet 8 can be reduced as much as possible, it is possible not to form the rubber escape grooves 4 and 5 in any of the dies 1 and 6.

Further, in the above embodiment, each section 3 has a rectangular shape, and each rubber sheet 8 has a strip shape. However, the shapes of each section 3 and the rubber sheet 8 are arbitrary. Further, the cavities 2 included in each section 3 are not limited to two rows.

Further, in the above embodiment, the method of press-forming the O-ring has been described. However, the present invention can be similarly applied to a case where a large number of other rubber products are manufactured by press-forming the rubber sheet 8. In the above embodiment,
Although the rubber sheet 8 made of raw rubber is used, the present invention can be similarly carried out when a rubber sheet made of another synthetic rubber or the like is press-formed.

[0032]

As is clear from the above description, according to the method for press-molding a rubber product of the present invention, the number of unnecessary rubber sheets placed in each section or between each section is reduced, so that the press The pressing force at the time of molding can be reduced, and the press device can be made simple, compact, and inexpensive. In addition, if the same pressing force as in the related art is applied, the productivity of rubber products can be increased by forming more cavities. In addition, it is possible to reduce the thickness of the burrs attached to the rubber product, thereby reducing the time and effort for deburring. further,
Since the wear of the edge of the mold is reduced, the life of the mold can be prolonged and the production cost can be reduced. further,
The material yield of the rubber sheet can be increased, and the material cost can be reduced by using a rubber sheet having a low sheet thickness accuracy.

[Brief description of the drawings]

FIG. 1 shows one embodiment of the present invention, and is a perspective view of a lower mold.

FIG. 2 shows one embodiment of the present invention, and is a plan view of a lower mold.

FIG. 3, showing an embodiment of the present invention, is a longitudinal sectional view illustrating a state in which a rubber sheet is press-molded by upper and lower dies.

FIG. 4 shows a conventional example and is a perspective view of a lower mold.

FIG. 5 shows a conventional example and is a plan view of a lower mold.

FIG. 6 shows a conventional example, and is a longitudinal sectional view showing a state where a rubber sheet is press-formed by upper and lower dies.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Lower mold 2 Cavity 3 Section 4 Rubber escape groove 8 Rubber sheet

──────────────────────────────────────────────────続 き Continuation of the front page (56) References Japanese Utility Model Showa 61-919 (JP, U) Japanese Utility Model Showa 58-147725 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) B29C 43/00-43/58 B29C 33/42

Claims (2)

(57) [Claims] 1. A method for press-molding a rubber product in which a rubber sheet is placed on a mold surface of a mold provided with a number of cavities and pressed to form a rubber product. Surrounding the entire molding area of the molding die surface, further dividing the molding die surface into a plurality of sections each including a plurality of cavities, placing a rubber sheet slightly smaller than the section shape in each section, and pressing Press molding a rubber product. 2. The method according to claim 1, wherein the section is divided so as to include two rows of cavities, and a strip-shaped rubber sheet slightly smaller than the section is placed and pressed for each section. The method for press-molding a rubber product according to claim 1.