JPS6337217Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to an injection plunger for a transfer molding machine that performs transfer molding of rubber.

In a transfer molding machine that performs transfer molding of rubber, a rubber material is placed in a pot, and the pot or injection plunger is moved up and down to inject the rubber material in the pot from a sprue gate into a mold cavity under reduced pressure. , the seal between the injection plunger and the pot is suitable for continuous transfer molding.
The residual rubber material, i.e., cull, that adhered to the vicinity of the tip of the injection plunger during the previous operation is used as its sealing member.

However, as shown in FIG. 1, the injection plunger 1 in the conventional transfer molding machine of this type is only provided with a circumferential groove 2 on the outer periphery of its tip, and the cull is formed in the circumferential groove 2. However, when the pot is detached from the injection plunger, the sealing member of the cal attached to the injection plunger 1 comes off from the circumferential groove 2, and the pot and the bot are separated from each other during the next molding. There was a problem that made it impossible to seal between the injection plungers.

Therefore, this invention makes it possible to form a sealing member by reliably attaching cal to the outer periphery of the tip of the injection plunger during continuous transfer molding, and to ensure a seal between the injection plunger and the pot when they fit together. The purpose of the present invention is to provide an injection plunger for a transfer molding machine.

The present invention is constructed by drilling a plurality of holes inward from the outer periphery of the tip of the plunger body, and providing a through groove between these holes and the bottom surface of the plunger body.

Hereinafter, embodiments of this invention will be described based on the drawings.

FIG. 2 is a front view of the injection plunger of the transfer molding machine, and FIG. 3 is a bottom view of the injection plunger, in which six holes are drilled at 60 degree intervals on the outer periphery of the tip of the plunger body 3. These holes 4 are bored in the radial direction from the outer periphery, that is, toward the interior center, and have a depth of about 1/7 of the diameter of the plunger body 3. moreover,
A slit-shaped through groove 5 is bored between these holes 4 and the bottom surface of the plunger body 3. Therefore,
In reality, for example, if a hole with a diameter of 8 mm is drilled on the outer periphery of the tip of a plunger body with a diameter of 50 mm, the depth of the hole is 7 mm, and the diameter is 2.5 mm to 3 mm.
It is sufficient to provide a through groove having a width of . Note that the number and size of the holes 4 and the width of the through groove can be determined as appropriate depending on the diameter of the plunger body 3 and the viscosity of the rubber material, but in any case, the fit between the plunger body 3 and the pot At times, it is necessary to make the cull act reliably as a sealing member on the outer circumference of the tip of the plunger body 3, and when changing the rubber material, it is necessary to determine the size and width to the extent that adhering cull can be easily removed by hand.

FIG. 4 shows a cross-sectional view of the open mold transfer molding machine, where 6 is a pot, and a seal plate 7 and a heat insulating plate 8 are fixed to the bottom of the pot block 6a.
A metal reinforcing member 9 is attached to the central bottom of the heat insulating board 8, and a sprue gate 11 is formed by a sprue bush 10 passing through the seal plate 7, the insulating board 8, and the reinforcing member 9. 12 is a gasket fitted around the heat insulating board 8 so as to protrude downward; 13 is a suction air passage for reducing the pressure inside the cavity; 14 is an upper mold; the lower mold and a movable plate that supports it are Illustrations are omitted.

When transfer molding of rubber is performed, the rubber material is put into the pot 6, a movable surface plate (not shown) rises, the lower mold and the upper mold 14 are brought together, and the upper mold 14 is placed at the bottom of the pot 6. The pot 6 rises when it hits the injection plunger, and the pot 6 is fitted into the injection plunger that is stationary upward, and the plunger body 3 is relatively moved up to the pot 6.
The rubber material is inserted into the sprue gate 11 and pressurized, and the rubber material is injected from the sprue gate 11 into the cavity below. At this time, the outer periphery of the tip of the plunger body 3 is filled with cal from the previous transfer molding and forms an annular sealing member 15, so that the sealing between the injection plunger and the pot 6 is reliably performed, and the inside of the cavity is sealed. It is possible to quickly bring the pressure down to a reduced pressure state and perform good transfer molding.

When the injection of the rubber material is completed and the movable surface plate is lowered and the tip of the plunger body 3 is pulled out from the pot 6 and the surrounding area is opened, the rubber material that was pressurized in the hole 4 is pushed out from the through groove 5. Well, this is the fourth
As shown in the figure, a good sealing member 15 is formed by a cull that spreads around the outer periphery of the tip of the injection plunger 3 and extends from the tip to the side surface. Then, the rubber material is put into the pot 6 again, and the transfer molding is performed in the same way. However, when the rubber material is changed and the molding operation is performed, the cul attached to the plunger body 3 can be easily removed by hand. be able to.

As explained above, according to the injection plunger of this invention, a plurality of holes are bored inward from the outer periphery of the tip of the plunger body, and a through groove is provided between these holes and the bottom surface of the plunger body. did.
Therefore, by relatively simple machining of the plunger body, it is possible to form a sealing member by reliably attaching cal to the outer periphery of its tip, and to perform a good seal without the sealing member coming off even when the injection plunger and pot are separated. I can do it. Furthermore, when changing the rubber material, the cull seal member can be easily removed manually.

[Brief explanation of drawings]

Figure 1 is a front view of a conventional injection plunger, Figure 2 is a front view of a conventional injection plunger;
The figure is a front view showing an embodiment of the present invention, FIG. 3 is a bottom view of the same, and FIG. 4 is a sectional view of the transfer molding machine when the mold is opened. 3... Plunger body, 4... Hole, 5... Penetration groove.

Claims (1)

[Scope of utility model registration request] An injection plunger for a transfer molding machine, characterized in that a plurality of holes are bored inward from the outer periphery of the tip of the plunger body, and a through groove is provided between these holes and the bottom surface of the plunger body.