JPS62200075A - Forming method for oil seal - Google Patents

Abstract

PURPOSE:To reduce an injection pressure and to form an oil seal having a compact internal composition by slidably a piston capable of moving back under a low pressure into a cylinder which is formed as one of split molds which take partial charge in forming a cavity. CONSTITUTION:The injection of rubber substrate G for molding which is adequately plasticized is commenced from an injection nozzle 13 into the inner circumferential space of a cylinder 6. Following the injection, a piston 7 and a ram 8 move back donward to carry out the filling of rubber substrate G for molding. After completion of injection, when the ram 8 is energized upward by a high pressure, the rubber substrate G for molding in the cylinder 6 is pushed out into a cavity 4 through a gate 5 to be compressed, and the rubber substrate G being filled in the cavity 4 to be cured comes to have a high molecular density and compact internal composition in the same way as in the case of compression molding.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for forming an oil seal used as a shaft sealing means for one piece of equipment.

[Conventional technology]

Conventionally, injection molding has been adopted as one of the methods for forming oil seals.

Injection molding is a process in which molding rubber dough, which has been appropriately plasticized, is injected from an injection nozzle into a molding cavity of a split mold that has been clamped in advance to fill it in an injection machine.

[Problem that the invention seeks to solve]

However, in the above-mentioned injection molding method, the mold-clamped dough is injected into the molding cavity in advance, so a large injection pressure (1000~
1500 kg/Cm'), and unlike compression molding, it is not possible to obtain a molded product with a high density and an internal composition with little distortion due to molecular orientation. Problems such as wear resistance remained.

The present invention was made in view of these problems, and
The purpose is to lower the injection pressure and to form an oil seal with a dense internal composition.

[Means for solving problems]

In order to solve the above problems, the method for molding an oil seal according to the present invention includes forming a cylinder communicating with the cavity in one of the split molds each forming a cavity for molding the oil seal, and A piston capable of retracting under low pressure is slidably inserted into the cylinder, and after the mold is clamped in advance, the cylinder is completely injected and filled with rubber dough, and the piston, which has retracted due to the injection pressure, is returned by pressurizing means. By doing so, the rubber fabric is filled and compressed into the cavity.

[For production]

That is, when the split mold is clamped in advance and the piston in the cylinder is advanced toward the injection machine side, and the molding dough is injected into the cylinder, the piston moves backward accordingly, Furthermore, since the cylinder has a simple shape, injection filling can be performed at a relatively low injection pressure. After the injection is completed, when the piston is returned to the injection machine side by the pressurizing means, the rubber dough in the cylinder is injected with oil and filled into the seal molding cavity, and compressed accordingly. , an oil seal with a dense internal composition can be obtained.

〔Example〕

Hereinafter, one embodiment of the present invention will be described based on the drawings.

Symbols (1) to 3) in each figure indicate a split type that is assembled vertically and removably to form an annular oil seal molding cavity (4) at the joint. A cylinder (6) is formed through the center of the mold (3) and communicates with the cavity (4) via a gate (5). A piston (7) fixedly attached to the ram (8) and moving together with the ram (8) is slidably inserted, and between the ram (8) and the split mold (3), A clamping spring (9) is loaded to apply clamping pressure between the divided molds (1), (2), and (3). Fixed 8
A sprue (11) into which an injection nozzle (13) of an injection machine is inserted and removed is formed in the upper split mold (1) fixedly installed on the board (10), and the sprue (11) has an injection port (12). It communicates with the cylinder (6) through the cylinder. (eye) is a piston (7)
and a vacuum nozzle provided through the ram (8).

To mold an oil seal using the molding machine with the above configuration, first, as shown in Figure 1, move the ram (8) upward with a force slightly greater than the elastic force of the mold clamping spring (9). By energizing, the split molds (+) (2) and (3) are clamped, the piston (7) is positioned at the upper limit of the stroke in the cylinder (6), and the injection nozzle (+3) is fitted into the sprue (11). After the cavity (4) is evacuated from the nozzle (14) by a vacuum pump (not shown) or the like, as shown in FIG. Injection of the plasticized rubber material for molding (G) is started. In this case, the injection pressure may be relatively small; in other words, during injection, the piston (7) and the ram (8) are directed downward by the combined force of the pressure and the elastic force of the mold clamping spring (9). Further, since the cylinder (6) has a simple shape, it is possible to fill the cylinder (8) with the molding rubber dough (G) even at a low pressure of about 150 to 350 kg/cm''. At this time, the divided molds (+) (2) and (3) are held in a low-pressure mold clamping state by the elastic force of the mold clamping spring (9).After the injection is completed, as shown in Figure 3. , rum (
8) is forced upward with high pressure, the piston (7) sliding upward in the cylinder (8) together with the ram (8) causes the rubber dough (G) for molding in the cylinder (6) to pass through the gate ( 5) into the cavity (4) and is compressed, and the divided molds (+) (2) and (3) are also clamped under high pressure. Therefore, in the compressed state shown in FIG. 4, the rubber fabric (G) is filled into the cavity (4) and hardened.
As in the case of compression molding, the molecular density is high and the internal composition is dense. After the rubber dough (G) has hardened, the split molds (1), (2), and (3) are separated as shown in FIG. 5, and then the mold release device i! In step (15), the oil seal molded product (Go) is released from the mold, and the process proceeds to the next step (paris removal step), which is not shown.

〔Effect of the invention〕

As explained above, the oil seal molding method according to the present invention first injects the molding rubber dough from the injection nozzle into a cylinder in a split mold in which a piston that operates backward at low pressure is inserted. The rubber dough can be injected at a significantly low injection pressure, so there is no need for a high-output injection machine, and the rubber dough once filled into the cylinder is filled into the cavity and compressed by the pressure return of the piston. At this time, the clamping pressure of the split mold is also large, so as in the case of compression molding, the internal composition of the molded product becomes dense and has excellent wear resistance. This has extremely great effects such as being able to obtain an oil seal.

[Brief explanation of drawings]

The drawings are all cross-sectional views of essential parts to explain the operation of the oil seal molding machine used in the molding method of the present invention. Figure 1 shows the mold clamping and vacuuming process, and Figure 2 shows the rubber dough injection process into the cylinder. , the third factor is the compression process by the piston, FIG. 4 shows the compression completed state, FIG. 5 shows the mold opening process, and FIG. 6 shows the mold release process. (1) (2) (3) Split type (0 cavity (5) gate (8) cylinder (7) piston (8) ram (8) mold clamping spring (1G) fixed hot plate (11) sprue (12) injection Outlet (+3) Injection nozzle (14
) Vacuum nozzle (15) 111i type device (G)
Rubber fabric (Go) Oil seal molded product Figure 1 Figure 5 Figure 6 Figure 1c;

Claims (1)

[Claims] One of the split molds (3), which is formed by sharing the cavity (4) for molding the oil seal, has a cavity (4).
), and a piston (6) capable of retracting at low pressure into the cylinder (6).
7) is slidably inserted and the mold is clamped in advance, then the rubber dough (G) is injected and filled into the cylinder (6), and the piston (7), which has retreated due to the injection pressure, is returned to its original position by a pressurizing means. A method for molding an oil seal, which comprises filling and compressing a rubber dough (G) into a cavity (4).