JPH0661804B2 - 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 glass fibers in a lump form such as Compound).

[Prior Art] Molding materials in which glass fibers are mixed with synthetic fibers such as unsaturated polyester have various compositions and properties depending on applications and molding methods.

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 glass fiber as the raw material, but it is also related to the molding method, and it is important to use a molding method with as few breakages as possible. Is necessary to improve the mechanical properties of.

The applicant of the present invention has proposed a rotary plunger type injection molding machine shown in FIGS. 2 and 3 as an injection molding machine suitable for such molding in JP-A-62-122729.

In FIG. 2, a cylindrical barrel 2 having a nozzle 1 at its tip and a temperature control device at a relatively low temperature on its outer periphery is
It is arranged so that the nozzle 1 can face the material injection port of the mold.

In the barrel 2, a plunger 4 having an outer diameter smaller than the inner diameter of the barrel 2 and having a backflow prevention mechanism composed of a check ring 3 near the tip is provided so as to be able to move forward and backward and to rotate. A material passage 5 is formed between the inner peripheral surface of the barrel 2 and the outer peripheral surface of the plunger 4. At the material inlet 6 on the rear side of the barrel 2, a stuffer type material supply device having a stuffer plunger 8 in a stuffer 7 is provided. The rear end of the plunger 4 is barrel 2.
More protruding, plunger rotation and forward / backward movement mechanism (not shown)
Have been serialized.

As shown in FIG. 3 (cross-sectional view taken along the line III-III in FIG. 2), a stopper portion 9 for preventing the check ring 3 from coming off is provided at the tip portion of the plunger 4. In FIG. 9, three claws 9 a are provided so as to project from the plunger 4 in the radial direction.

In the injection molding machine having such a configuration, when the stuffer plunger 8 for supplying the material is advanced with the plunger 4 located in the front in the barrel 2 being rotated, the material is supplied to the material inlet portion 6 and the material. It is supplied to the tip portion in the barrel 2 through the passage 5 and the check ring 3 portion. If the desired amount of BMC, etc. accumulates in front of the barrel 2, the measurement ends, and then
When the plunger 4 is moved forward, the material is ejected from the nozzle 1, but in this case, the material that has entered the passage 5 first comes out first. Further, the rotation of the plunger 4 makes the material flow extremely smooth and uniform. This plunger type injection molding machine has a characteristic that the metering capacity increases as the number of rotations increases, even though there is no portion corresponding to a screw type flight.

[Problems to be Solved by the Invention] According to the structure shown in FIG. 2 proposed in Japanese Patent Laid-Open No. 62-122729, a molded product having excellent performance can be obtained. It was recognized that it had the improvement task mentioned.

That is, in the structure shown in FIG. 2, since the material is pushed into the barrel 2 by the stuffer plunger 8, a large bending force that pushes downward is applied to the rotating cantilevered plunger 4. The rotation of the plunger 4 is continued while keeping the tip of the plunger 4 lowered. Therefore, a large repetitive load acts on the rotating plunger 4, and it is necessary to increase the diameter of the plunger 4 and the like to improve the strength. Therefore, it was necessary to narrow the material passage 5 or increase the inner diameter of the barrel 2.

Further, in molding the resin containing glass fiber, it is necessary to prevent the glass fiber from being cut in the barrel 2 as much as possible.

[Means for Solving the Problem] In order to solve such a problem, in the present invention, a barrel having a material inlet portion on the rear end side, and a peripheral surface of the barrel and the inside of the barrel which are inserted into the barrel are provided. A plunger that has a diameter that forms a passage of material between it and the peripheral surface, and whose rear end is connected to a drive device to rotate and move forward and backward, and the outer circumference near the tip of the plunger, and the inner circumference of the barrel. The check ring is slidably mounted on the surface, and the check part is provided on the rear side of the check ring so that the rear surface of the check ring can be in close contact with the outer periphery of the plunger. Has a stopper part for preventing the check ring from coming off at least at two places, and is provided in a convex shape at least at three places in the circumferential direction of the outer peripheral part of the plunger on the rear side of the check part. , Outer peripheral tip There is provided slidably in close contact with the inner peripheral surface of the barrel,
In addition, the supporting piece has a planar shape that narrows toward the rear side.

[Operation] In the injection molding machine of the present invention employing the above structure,
When the plunger in the barrel is rotated, the material is pushed into the barrel by the action of the stuffer plunger, the retracting of the plunger causes the weighing, and the advancing of the plunger causes the injection.

When the material is pushed into the barrel by the action of the stuffer plunger, the pressing force acts on the rotating plunger, but since the supporting piece at the tip of the plunger is provided, the bending that acts on the plunger. The stress is relieved significantly.

Further, since the planar shape of these supporting pieces is narrowed toward the rear side, the contained glass fiber resin smoothly passes between the supporting pieces, and it is possible to cut or lose the glass fibers as much as possible. It is held down.

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

FIG. 1 is an overall cross-sectional view showing the structure of an injection molding machine according to an embodiment of the present invention, FIG. 4 is an enlarged view of an essential part of FIG. 1, and FIG. 5 is a view of FIG. The left side view and FIG. 6 are sectional views taken along line VI-VI in FIG.

In FIG. 1, reference numeral 2 is a barrel, and the tip is an injection nozzle 1. The barrel 2 has a relatively low temperature heater on its outer peripheral portion. The barrel 2 is arranged so that the nozzle 1 can face the material injection port of the fixed mold 11 attached to the fixed platen 10. 12 is a column, 13
Is a column nut, 14 is a machine base of the mold clamping device side, 1
5 is a machine base on the injection device side, 16 is a machine base 1
5, a loading base 17 and a motor holding member 18 of the barrel 2 are slidably mounted on the block 16. 19 is a block 16 attached to the fixed platen 10.
A cylinder for movement, 20 is a piston rod, and the tip end of the piston rod 20 is fixed to the block 16,
The nozzle 1 is fixed to the fixed mold 1 by the operation of the moving cylinder 19.
It can be brought into contact with No. 1 or retracted to the illustrated state.

A plunger 4 is provided in the barrel 2 so as to be movable forward and backward and rotatably. A material passage 5 is provided between the inner peripheral surface of the barrel 2 and the outer peripheral surface of the plunger 4. A rotary drive device such as a hydraulic motor 22 is connected to the plunger 4 via a motor holding member 18 and a bearing housing 21. Further, an injection cylinder 23 and a piston rod 24 are attached between the motor holding member 18 and the loading base 17.

At the center of the plunger 4, a convex portion 25 that is in contact with the inner peripheral surface of the barrel 2 is provided. Further, a screw 26 for discharging the leak material is provided on the rear side of the convex portion 25 of the plunger 4. The screw 26 is for smoothly discharging the leak material leaked rearward from the clearance portion between the outer peripheral surface of the convex portion 25 and the inner peripheral surface of the barrel 2 to the rear side of the barrel 2, and The direction of rotation is opposite to the direction of rotation.

A stuffer 7 is provided vertically at the material inlet 6 on the rear side of the barrel 2, and a stuffer plunger 8 for pushing down the material is provided therein. Reference numeral 27 is an inlet for material supply provided on the side surface of the stuffer 7. 28 is a cylinder for the stuffer plunger 8, 29 is a piston rod,
30 is a connecting member.

As shown in FIGS. 4 and 5, a small diameter portion 4a is provided near the tip of the plunger 4, and a check portion 4b made of a tapered portion is provided behind the small diameter portion 4a. . A check ring 5 slidably provided on the inner peripheral surface of the barrel 2 is arranged on the outer periphery of the small-diameter portion 4a, and a taper portion provided on the rear end-side inner peripheral surface of the check ring 5 has a check portion. It can come into close contact with 4b.

Stoppers 30 for preventing the check ring 5 from coming off are provided at two positions in the circumferential direction of the tip of the plunger 4.

On the outer peripheral portion of the plunger 4 on the rear side of the check portion 4b of the plunger 4, convex supporting piece portions 31 are provided at three circumferential positions at equal intervals. Is slidably provided in close contact with the inner peripheral surface of the barrel 2. Therefore, the support structure of the plunger 4 has the convex portion 25.
The support piece 31 has a two-sided support structure.

As shown in FIG. 6, the planar shape of these support piece portions 31 is such that it narrows toward the rear side, that is, the material supply side.

The planar shape of the support piece portion 31 may be a shape close to a rhombus, as shown in FIG.

What is shown in FIG. 8 is a state in which the planar shape is twisted in a direction opposite to the rotation direction of the plunger 4.

By doing so, the material passages 5 on both sides of the supporting piece portion 31 are formed.
The glass fiber in the material is not broken so that the material flows smoothly.

Next, the operation of the apparatus shown in FIGS. 1, 4 and 5 will be described.

First, while the plunger 4 is positioned at the forward limit, the material such as BMC contained in the stuffer 7 is pushed down by the action of the stuffer plunger 8 while the plunger 4 is rotated at, for example, 5 to 100 rpm. Then, the material enters the barrel 2 through the material inlet portion 6 and is forwarded through the material passage 5 on the outer peripheral portion of the plunger 4. At this time, the check ring 3 is pushed forward and locked by the rear surface of the stopper portion 30, and the material is the passage 5 between the support piece portions 31, the inner peripheral surface of the check ring 3 and the small diameter portion 4a of the plunger 4. It is stored in the inside of the tip of the barrel 2 through the passage between the and, and the passage between the stopper portions 30, and the measuring process proceeds.

In this measuring step, the plunger 4 is gradually retracted by being pressed by the material stored in the tip of the barrel 2. At this time, the injection cylinder 23 connected to the rear of the plunger 4
In addition, by supplying the minimum necessary hydraulic pressure in the direction opposite to the back pressure, the retracting resistance of the plunger 4 can be reduced, the force applied to the material can be reduced, and the damage of the glass fiber can be prevented. When the risk of damage to the glass fiber is small, back pressure can be applied to the material by supplying hydraulic pressure in the back pressure direction to the injection cylinder 23.

Due to the rotation of the plunger 4, the resin material around the plunger 4 is homogenized and short circuit of the flow path of the material is prevented. Also, due to the pressing action of the stuffer plunger 8 and the rotating action of the plunger 4, the material does not pass only through the material passage 5 on the side of the plunger 4, but also flows into the material passage 5 below the plunger 4. It is pushed in such a state,
In addition, since the material is sent while wrapping around from the lower side to the upper side of the plunger 4 or from the upper side to the lower side, even the material that is difficult to flow does not stay in the barrel 2 and the entire inner circumference of the barrel 2 is smoothed. Be transferred. When the material is provided near the tip of the plunger 4 and passes through the passage between the support piece portions 31, the rear side of the support piece portion 31 is flat and narrow. Since it moves forward along the streamlined side face, the glass fiber flows more smoothly without damage.

The stopper portion 30 provided at the tip of the plunger 4
However, if the planar shape is made narrower on the rear side, the material can be made to flow more smoothly and the damage to the glass fiber can be suppressed accordingly.

Since the stuffer plunger 8 exerts a pressing action while the plunger 4 is rotating, bending stress acts on the plunger 4, but near the tip of the plunger 4,
Since the convex support piece portion 31 whose outer peripheral tip surface is closely slidably provided on the inner periphery of the barrel 2 is provided, the plunger 4 has a double-sided support structure, and the plunger 4 can be smoothly moved. As it rotates, it also has a longer life. Further, since the plunger 4 is also strong against bending stress, the device itself can be made compact.

After a predetermined amount of material is weighed in the barrel 2, the injection cylinder 23 advances the motor holding member 18. As a result, the plunger 4 integrated with the holding member 18 advances.
Then, the check ring 3 retracts, and the taper surface on the rear side thereof comes into close contact with the check portion 4b at the tip of the plunger 4 to close the material retreat path. Then, when the plunger 4 is further advanced by the injection cylinder 23, the material weighed in the barrel 2 is injected.

[Effects of the Invention] As is clear from the above examples, in the injection molding machine of the present invention, since the supporting piece is provided near the tip of the plunger, the plunger has a double-sided support structure, and the bending stress of the plunger is also reduced. It is relaxed and its durability is enhanced. Moreover, since the planar shape of the support piece portion is narrowed toward the rear side, the effect of preventing damage to the glass fiber contained in the material is exhibited.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing an embodiment of the present invention, FIG. 2 is a vertical sectional view showing an example of a prior art similar to the present invention, and FIG. 3 is a sectional view taken along line III-III of FIG. 4, FIG. 4 is an enlarged view of a main part of FIG. 1, FIG. 5 is a left side view of FIG. 4 with a check ring removed, and FIG. 6 is a sectional view taken along line VI-VI of FIG.
FIGS. 8 and 9 are sectional views showing other embodiments of the portion corresponding to FIG. 2 ... Barrel, 3 ... Check ring, 4 ... Plunger, 4b ... Check part, 5 ... Material passage, 6 ... Material inlet part, 8 ... Staffer plunger, 9, 30 ... Stopper part , 19-moving cylinder, 22-hydraulic motor, 23-injection cylinder, 31-supporting piece.

Claims (1)

[Claims] 1. A barrel having a material inlet portion on the rear end side, a barrel having a diameter that is inserted into the barrel and forms a passage for the material between the peripheral surface and the inner peripheral surface of the barrel, and , A plunger whose rear end is connected to a drive device to rotate and move forward and backward, a check ring slidably provided on the inner peripheral surface of the barrel at the outer periphery near the tip of the plunger, and a rear side of the check ring. On the outer periphery of the plunger, there are a check part so that the rear surface of the check ring can be in close contact with it, and a stopper part for preventing the check ring from coming off at least at two positions in the circumferential direction at the tip of the plunger. It is provided with a convex shape at least at three circumferential positions on the outer peripheral portion of the plunger on the rear side of the check portion, and the outer peripheral end surface is slidably in close contact with the inner peripheral surface of the barrel. Is provided,
Also, an injection molding machine having a supporting piece portion whose planar shape is narrowed toward the rear side.