JPH0628883B2 - Injection molding machine - Google Patents

Description

The present invention relates to an injection molding machine, and more particularly to BMC (Bulk Molding).
The present invention relates to an injection molding machine suitably used for a molding material containing a glass fiber such as a compound.

[Prior Art] A molding material in which a synthetic resin such as unsaturated polyester is mixed with glass fiber has various compositions depending on the use and the molding method.
There is a property.

The mechanical properties of the molded product have a strong correlation with the state of the glass fiber of the molded product, the longer the fiber length and the more unbent,
Mechanical strength is improved.

The length of the glass fiber in the molded product is of course related to the length of the raw material glass fiber, but it is also related to the molding method, and it is important to use a molding method with as few breakages as possible. It is necessary to improve mechanical properties.

Plunger type molding machine has less breakage of glass fiber and less bending than screw type. However, in spite of these advantages, the plunger type molding machine is rarely adopted in practice. This is because of the structural drawbacks described below. Figures 5 and 6 show the general structure of the plunger type.

FIG. 5 is a schematic configuration diagram of a conventional plunger-type injection molding machine. The molding machine 1 includes a stuffer 3 and a barrel 4 connected by an elbow 2. The plunger 6 of the cylinder 5 is reciprocally fitted therein. The plunger 8 of the injection cylinder 7 is fitted in the inner hole of the barrel 4, and the material supply port 9 from the stuffer 3 is opened in the middle of the inner hole near the nozzle 10. Reference numeral 11 is a check valve for preventing backflow of material. With this structure, when the material 12 is put into the stuffer 3 and the plunger 6 of the supply cylinder 5 is advanced, the material 12 is supplied to the barrel 4 from the material supply port 9 through the elbow 2. Check valve 11
Backflow is regulated by. Then, by moving the plunger 8 of the injection cylinder 7 forward, the material 12 in the barrel 4 can be injected from the nozzle 10 into the mold.

Further, FIG. 6 is a schematic configuration diagram showing another example of a conventional plunger type injection molding machine, and the components denoted by the same reference numerals as those in FIG. 5 have the same structure, and therefore the description thereof will be omitted. This example is different from the example shown in FIG. 5 in that the material supply port 9A from the stuffer 3 is opened at the end of the barrel 4A on the side opposite to the nozzle 10 and the check valve 11 is not provided. . The material 12 is supplied into the barrel 4A by the advance of the plunger 6, and the injection is performed by the advance of the plunger 8, as in the example shown in FIG.

However, in the conventional molding apparatus shown in FIG. 5, since the material supply port 9 is provided near the nozzle 10, the back pressure can be applied by the injection cylinder 7 when the material 12 is metered and supplied from there. However, on the other hand, the material 12 that has entered from the material supply port 9 to the inner hole of the barrel 4 faces the plunger 8 side, and the material 12 that has entered afterwards is the nozzle 1
The material 1 that entered first when it was ejected
Since 2 comes out later, there is a drawback that the material 12 tends to stay.

Further, in the structure shown in FIG. 6, the material supply port 9A is provided near the plunger 8 and the plunger 8 is retracted for each shot to supply the material 12, so that the material 12 that has entered first is supplied. However, since back pressure cannot be applied, there is a disadvantage that the metering of the material 12 to be supplied becomes unstable and that air is easily entrained.

The present applicant has proposed a rotary plunger type injection molding machine shown in FIG. 7 in Japanese Patent Application Nos. 60-79197 and 60-168898 as means for solving these drawbacks.

In FIG. 7, a cylindrical barrel 22 having a nozzle 21 at its tip and a relatively low temperature control device at its outer periphery.
Are arranged so that the nozzle 21 can face the material injection port of the mold.

In the barrel 22, a plunger 24 having an outer diameter smaller than the inner diameter of the barrel 22 and having a backflow prevention mechanism including a check ring 23, a ball and the like near the tip is provided so as to be able to move forward and backward and to rotate. Between the inner peripheral surface of the barrel 22 and the outer peripheral surface of the plunger 24.
Are formed. At the material inlet portion on the rear side of the barrel 22, for example, a stuffer type material supply device having a stuffer plunger 30 in a stuffer 27 having a material inlet 31 as shown in the drawing is provided. (The material supply device may be another type of device, such as a type having a sufficient material supply capacity such as a screw feeder.) As shown in the drawing, the plunger 24 has a rear end side substantially equal to the barrel inner diameter. The convex portion 25 has a diameter increased so as to have the same diameter. The convex portion 25 slides on the inner peripheral surface of the barrel 22, and holds the plunger 24 so that the plunger 24 is arranged substantially coaxially with the barrel 22. The further rear end side of the plunger 24 projects from the barrel 22 and is connected to a plunger rotation and forward / backward movement mechanism (not shown).

In the injection molding machine having such a configuration, when the stuffer plunger 30 for material supply is advanced with the plunger 24 located in the front of the barrel 22 of the injection cylinder being rotated, the material is supplied while being metered. Mouth 28,
The material is supplied to the tip of the barrel of the injection cylinder through the material passage 70 and the backflow prevention mechanism 23. When a desired amount of BMC or the like has accumulated in the front of the barrel 22, the measurement is finished, and then, when the plunger 24 is advanced, the material is injected from the nozzle 21, but in this case, the material that has entered the material passage 70 first. Get out. Also, the rotation of the plunger 24 makes the material flow extremely smooth and uniform. This plunger type injection molding machine has a characteristic that the metering capacity increases almost in proportion to the number of rotations, although there is no portion corresponding to a screw type flight.

[Problems to be Solved by the Invention] According to the above structure proposed in Japanese Patent Application Nos. 60-79197 and 60-198898, a glass fiber is less damaged and a molded article having excellent performance is obtained. However, it was recognized that this type has the following improvement problems.

That is, when the material is supplied from the material supply device (stuffer 27) into the barrel 22, bending stress is generated in the plunger 24 due to the force of pushing the plunger downward from above. If this bending stress is excessive, the plunger 24
May be damaged by repeated bending stress. Further, this bending stress is received by the convex portion 25 at the rear portion of the stuffer, but excessive bending stress causes galling. In addition, the resistance of the plunger 24 for retracting becomes large at the time of weighing, and if it is excessively large, it causes breakage of the glass fiber.

That is, as shown in FIG. 8 (a), the plunger diameter b
Compared with the above, a is smaller, and because it cannot withstand bending stress, it is not supported at both ends but cantilevered, so it is weak in strength.
The provision of the virtual pin-shaped protrusions 32 ′ provides support at both ends, reducing bending stress, but increasing the number of places where the material flowing through the material passage is divided, and increasing the damage to the glass fibers.

In addition, this type of injection molding machine is different from the screw type in that most of the material metering action is performed by pressurization from the material supply device. Supply pressure) is higher than normal screw type. This point also contributes to an increase in the galling of the convex portion 25 and the damage phenomenon of the glass fiber.

[Means for Solving the Problems] In order to solve the above problems, the present invention relates to an injection molding machine in which a plunger is inserted in the barrel and a material pressing and supplying device is connected to the rear side of the barrel. The plunger is provided with a pin-shaped projection that is used in combination with a material backflow prevention mechanism provided in the material flow path in the barrel and that supports the plunger against the inner peripheral surface of the barrel.

[Operation] In the injection molding machine of the present invention employing the above structure,
The stress state generated in the plunger changes from "cantilever" to "both ends supported" or "equal distribution", and bending stress is reduced. Further, the force generated on the convex portion at the rear part of the plunger is reduced, the occurrence of galling is prevented, the backward resistance of the plunger is also reduced, and the damage of the glass fiber can be reduced.

Embodiments Embodiments will be described below with reference to the drawings.

FIG. 1 is a full sectional view showing a structure of an injection molding machine according to an embodiment of the present invention, FIG. 2 is an enlarged sectional view of an essential part of the same, FIG. 3 is a drawing showing a state of a check ring during weighing, and FIG. Fig. 2
FIG. 4 is a sectional view taken along the line IV-IV.

In FIGS. 1, 2, and 3, a nozzle 21 is provided at the tip,
Cylindrical barrel 2 having a relatively low temperature heater on the outer periphery
No. 2 is arranged so that the nozzle 21 can face the material injection port of the fixed mold 61 attached to the fixed plate 60. 62 is a column, 63 is a column nut, 64 is a machine base on the mold clamping device side, 65 is a machine base on the injection device side, 66 is a block slidably provided on the machine base 65 in the axial direction, and the block 66 The barrel 22 is fixed to the front of the above, and the motor holding member 67 is slidably attached to the rear of the above. 68 is a fixed plate 6
A cylinder for moving the block 66 fixed to 0, 69 is a piston rod, and the tip end of the piston rod 69 is fixed to the central portion of the outer surface of the block 66.
By the operation of No. 8, the nozzle 21 can be brought into contact with the fixed mold 61 or retracted to the illustrated state.

In the barrel 22, a plunger 24 having an outer diameter smaller than the inner diameter of the barrel 22 and having a backflow prevention mechanism including a check ring 23 and the like near the tip is provided so as to be able to move forward and backward and rotatably. Then, the material passage 70 is provided between the inner peripheral surface of the barrel 22 and the outer peripheral surface of the plunger 24. A shaft of a rotary drive device such as a hydraulic motor 35 fixed to the motor holding member 67 is connected to the rear of the plunger 24 via a bearing 71 in the motor holding member 67. An injection cylinder 72 and a piston rod 73 are attached between the barrel 22 and the lower side of the motor holding member 67.

At the center of the plunger 24, a convex portion 25 that is in contact with the inner peripheral surface of the barrel 22 is provided. In addition, the convex portion 2 of the plunger 24
On the rear side of No. 5, a screw 29 for discharging the leak material was provided. The screw 29 includes the outer peripheral surface of the convex portion 25 and the barrel 2
The leak material leaked rearward from the clearance between the inner peripheral surfaces of the two is smoothly discharged rearward of the barrel 22, and is provided in a direction opposite to the rotational direction of the plunger 24.

Reference numeral 27 denotes a stuffer vertically provided in the material inlet portion 28 on the rear side of the barrel 22, and a stuffer plunger 30 for pushing down the material is provided therein. Reference numeral 31 is a material supply inlet provided on the side surface of the stuffer 27. 74
Is a cylinder for the stuffer plunger 30, which has a built-in piston 74a and is vertically attached to a part of the barrel 22 in an upward direction. 75 is a piston rod, and 76 is a connecting member.

As shown in FIG. 2, a material backflow prevention mechanism using the pin-shaped projection 32 as a stopper of the check ring 23 is provided in the portion near the tip of the plunger 24. Is held against the inner peripheral surface of the barrel 22. Therefore, this plunger 24
Are arranged in a state in which they are held by the convex portion 25 and the pin-shaped projection 32.

In the apparatus shown in FIG. 1, the material such as BMC is loaded into the stuffer 27 while the plunger 24 is positioned at the forward limit and is rotated at, for example, 3 to 100 rpm, and the material is fed by the stuffer plunger 30. Push down. Then, the material is sent forward through the outer periphery of the plunger 24. The check ring 23 moves forward relative to the plunger 24 (state of FIG. 3), passes through the clearance 33 generated at this time, and the material is successively accumulated in the barrel 22 in front of the plunger 24. At this time, the amount of forward movement of the check ring 23 is determined by the pin-shaped protrusion 32.
Is regulated as a stopper. Of course, in this measuring process, the plunger 24 is gradually retracted.

At this time, the back pressure can be applied to the material by controlling the hydraulic pressure in the rod end side chamber of the injection cylinder 72 connected to the rear of the plunger 24. Note that the back pressure can be applied to the material by friction between the outer peripheral surface of the convex portion 25 of the plunger 24 and the inner peripheral surface of the barrel 22, which retracts.

Due to the rotation of the plunger 24, the resin material around the plunger 24 is homogenized and the passage of the material is prevented from being shortened. Further, the pressing action of the stuffer plunger 30 and the rotating action of the plunger 24 cause the material to be
4, the material is pushed in such a manner that it does not pass only through the upper material passage 70 of the plunger 24 but also around the lower material passage 70 of the plunger 24, and the material is pushed from the lower side to the upper side of the plunger 24 or the upper side. Since it is sent while also wrapping around from the bottom to the lower side, the entire circumference of the barrel 22 can be smoothly transferred without staying in the barrel 22 even if the material is difficult to flow or the material is hard to flow.

[Effect] With the configuration as described above, even if the material is pressed and supplied from the stuffer 27 into the barrel 22 with a high supply pressure, the plunger 24 is held by the convex portion 25 and the pin-shaped projection 32. Since it is supported, the bending stress on the plunger 24 is reduced. Also, the stress of the convex portion 25 is reduced,
The galling is prevented, the retraction resistance of the plunger 24 is reduced, and the damage of the glass fiber contained in the material is also reduced.

[Brief description of drawings]

1 is an overall longitudinal sectional view showing an embodiment of the present invention, FIG. 2 is an enlarged sectional view of a plunger portion of FIG. 1, FIG. 3 is an enlarged sectional view of the same plunger portion, and FIG. IV- in the figure
Sectional views taken along line IV, FIG. 5, FIG. 6 and FIG. 7 are sectional views showing the prior art. 8 is a partially enlarged sectional view of FIG. 7, and FIG. 8 (b) is an axial front view of FIG. 8 (a). 22 ... Barrel, 23 ... Check ring, 24 ... Plunger, 27 ... Staffer, 30 ... Staffer plunger, 32 ... Pin-shaped projection, 70 ... Material passage.

Claims (1)

[Claims] 1. A barrel having an injection port at the tip and a material inlet at the rear side, and a barrel inserted into the barrel, forming a material passage between its peripheral surface and the barrel inner peripheral surface. A plunger having a diameter and a rear end side thereof connected to a drive device to reciprocate in the barrel; a material pressing and supplying device connected to a material inlet portion of the barrel; and a material flow path in the barrel. And a material backflow prevention mechanism provided on the plunger, which is used in combination with the material backflow prevention mechanism, the pin-shaped projection for supporting the plunger against the inner peripheral surface of the barrel being provided on the plunger. Molding machine.