JPH0479815B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an injection molding machine, and in particular to a BMC (Bulk
This invention relates to an injection molding machine that is suitably used for bulk molding materials containing glass fibers, such as molding compounds.

[Prior Art] Molding materials made of synthetic resins such as unsaturated polyester mixed with glass fibers have various compositions and properties depending on the application and molding method.

The mechanical properties of a molded article are highly correlated with the condition of the glass fibers in the molded article; the longer the fiber length and the less bent, the better the mechanical strength.

The length of glass fiber in a molded product is not only related to the length of the raw glass fiber, but also to the molding method, and it is important to use a molding method that minimizes breakage as much as possible. It is necessary to improve mechanical properties.

Plunger type molding machines have less breakage and bending of glass fibers than screw type molding machines. However, despite these advantages, plunger type molding machines are rarely employed in practice. This is due to the following structural drawbacks. Figures 8 and 9 show the general structure of a plunger type.

FIG. 8 is a schematic diagram of a conventional plunger-type injection molding machine, and the molding machine 1 is equipped with a stuffer 3 and a barrel 4 connected by an elbow 2. 5 plungers 6 are fitted so as to be reciprocally movable. Further, a plunger 8 of an injection cylinder 7 is fitted into the inner hole of the barrel 4, and a material supply port 9 from the stuffer 3 is opened at an intermediate portion of the inner hole near the nozzle 10. 11 is a check valve for preventing material backflow. With this configuration, when the material 12 is introduced into the staff 3 and the plunger 6 of the supply cylinder 5 is advanced, the material 12 is supplied into the barrel 4 from the material supply port 9 through the elbow 2. , check valve 11 restricts backflow. Therefore, the plunger 8 of the injection cylinder 7
By advancing the material 12 in the barrel 4
can be injected into the mold from the nozzle 10.

Further, FIG. 9 is a schematic configuration diagram showing another example of a conventional plunger type injection molding machine, and FIG.
Components with the same reference numerals as those in the drawings have the same structure, so the explanation thereof will be omitted. In this example, staff 3
The material supply port 9A from the nozzle 10 of the barrel 4A
It differs from the example shown in FIG. 8 in that it is open at the end opposite to the end and that there is no check valve 11. As in the example shown in FIG. 8, the material 12 is supplied into the barrel 4A by advancing the plunger 6, and injection is performed by advancing the plunger 8.

However, in the conventional molding apparatus shown in FIG. 8, the material supply port 9 is provided near the nozzle 10, so when the material 12 is metered and fed from there, back pressure is applied by the injection cylinder 7. However, on the other hand, the material 12 that enters the inner hole of the barrel 4 from the material supply port 9 first faces the plunger 8 side, and the material 12 that enters later faces the nozzle. 10
Since the material 12 that entered first comes out later during injection, there is a disadvantage that the material 12 tends to stay. Furthermore, since the seal portion of the plunger 8 passes through the material supply port 9 during injection, the seal portion is likely to be damaged.

Furthermore, in the device shown in FIG. 9, the material supply port 9A is provided closer to the plunger 8, and the plunger 8 is moved back for each shot to feed the material 12.
Since the material 12 is supplied first, the material 12 that entered first comes out first, but since no back pressure is applied, the metering of the supplied material 12 becomes unstable and there is also a drawback that air is likely to be drawn in.

As a means to solve these drawbacks, the applicant has proposed the
We proposed a rotating plunger type injection molding machine as shown in Figure 0.

In FIG. 10, a cylindrical barrel 22 having a nozzle 21 at its tip and a relatively low-temperature temperature control device at its outer periphery is arranged so that the nozzle 21 can face the material injection port of the mold. It is set up.

Inside the barrel 22, a plunger 24, which has an outer diameter smaller than the inner diameter of the barrel 22 and has a backflow prevention mechanism consisting of a check ring 23, a ball, etc. near its tip, is provided so as to be movable forward and backward as well as rotatable. The inner peripheral surface of the barrel 22 and the plunger 2
A material passage 70 is formed between the outer circumferential surface of 4 and the outer circumferential surface of 4. At the material inlet on the rear side of the barrel 22, there is provided, 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 figure. (The material supply device is, for example, a type that has sufficient material supply capacity such as a screw feeder, etc.)
Other types of devices may also be used. As shown in the figure, the plunger 24 has a convex portion 25 whose rear end side is enlarged in diameter to be approximately the same diameter as the barrel inner diameter. The convex portion 25 slides on the inner circumferential surface of the barrel 22 and holds the plunger 24 so that the plunger 24 is substantially coaxial with the barrel 22. Note that the rear end side of the plunger 24 protrudes from the barrel 22 and is connected to a plunger rotation and forward/backward movement mechanism (not shown).

In an injection molding machine having such a configuration, when the material supplying staff plunger 30 is advanced while the plunger 24 located at the front within the barrel 22 of the injection cylinder is rotated, the material is supplied while being measured. The material is supplied to the tip inside the barrel of the injection cylinder via the port 28, the material passage 70, and the backflow prevention mechanism 23. A desired amount of
Once BMC and the like have accumulated, the metering ends, and then when the plunger 24 is moved forward, the material is injected from the nozzle 21, but in this case, the material that entered the material passage 70 first comes out first. Moreover, the rotation of the plunger 24 makes the material flow extremely smooth and uniform. This plunger-type injection molding machine has the characteristic that its metering capacity increases as the rotational speed increases, even though it does not have a part corresponding to screw-type flights.

[Problems to be solved by the invention] According to the above-mentioned structure proposed in Japanese Patent Application No. 60-79197 and No. 60-168898, a molded product with excellent performance can be obtained with less damage to glass fibers. However, it was recognized that this type has the following improvement issues.

That is, as shown in FIG. 11 (a sectional view taken along the line - in FIG. 10), the tip of the plunger 24 includes:
A stopper portion for preventing the check ring 23 from coming off is provided, and this stopper portion is formed by several claws 24b protruding in the radial direction.

The stopper portion formed by such a claw 24b agitates the material as the plunger 24 rotates, causing damage to the glass fibers in the material.

Furthermore, in the injection molding machine of the prior application, material is stored at the tip of the barrel by retracting the plunger 24, so the plunger retraction stroke length is long to store the amount of material required for injection molding at the tip of the barrel. That is, the plunger 24 must be sufficiently long to ensure a long backward stroke length. Since the plunger is mechanically cantilevered, such a large shaft length is not structurally preferable.

Incidentally, this problem of a large shaft length is also common to injection molding machines of the type that use a screw instead of a plunger (for example, Japanese Patent Publication No. 46-2909).

[Means for Solving the Problems] The present invention provides an injection molding machine in which a plunger is inserted into the barrel and a material inlet is provided on the rear side of the barrel. Department)
At the same time, an enlarged diameter portion (valve body portion) that can be brought into close contact with the reduced diameter portion is provided at the tip of the plunger. and,
A forward and backward moving device is connected to the plunger, and the plunger is moved back and forth to bring the enlarged diameter portion and the reduced diameter portion into contact with and separate from each other, thereby opening and closing the material passage.

Further, a sleeve is fitted to the tip of the barrel so that it can freely slide in the axial direction of the barrel, and the tip of the sleeve is used as an injection port. Then, a barrel forward and backward moving device is connected to the barrel or the plunger, and by moving the barrel forward, the internal volume of the plunger and barrel located in front of the tip of the plunger is reduced to enable injection.

[Function] In the injection molding machine of the present invention employing the above structure, when the plunger is moved slightly forward or backward to separate the valve seat portion and the valve body portion, the raw material sent from the press feeding device is released. It becomes possible to pass between the valve seat portion and the valve body portion. Therefore, by gradually retracting the barrel, material can be stored in front of the plunger tip. (That is, the metering step is proceeded.) On the other hand, when the valve seat portion and the valve body portion are brought into close contact, the escape path of the material is cut off. Then, when the barrel is advanced, the material is injected from the sleeve injection port.

In this manner, in the device of the present invention, the metering step is performed by moving the barrel backward, and not by moving the plunger backward as in the conventional method, so that the length of the plunger can be short. Further, there is no need for a check ring holding claw at the tip of the plunger, and damage to the glass fibers can be reduced.

[Example] Examples will be described below with reference to the drawings.

FIG. 1 is an overall sectional view showing the structure of an injection molding machine according to an embodiment of the present invention, and FIG. 2 is an explanatory diagram of its operation.

Reference numeral 20 denotes a sleeve, the tip of which is an injection nozzle 21. This sleeve 20 has a cylindrical barrel 22 that has a relatively low temperature heater on its outer periphery.
The barrel 22 can be protruded and retracted from the tip of the barrel 22.
The inner circumferential surface of the barrel 22 and the outer circumferential surface of the sleeve slide through an appropriate sealing structure (not shown) so as to maintain a sealed state. This barrel 22 is arranged so that the nozzle 21 can face the material injection port of a fixed mold 61 attached to a fixed platen 60. 62 is column, 6
3 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 provided slidably in the axial direction on the machine base 65, and on top of the block 66 are: A sleeve support wall 20A is fixed to the front, and a loading base 80 of the barrel 22 and a motor holding member 67 are slidably attached to the rear thereof. 68 is a cylinder for moving the block 66;
9 is a piston rod, the tip of the piston rod 69 is fixed to a fixed plate 60, and the cylinder 6
8, the nozzle 21 can be brought into contact with the fixed mold 61 or retracted to the illustrated state.

A plunger 24 is provided within the barrel 22 so as to be movable back and forth and rotatable. A material passage 70 is provided between the inner peripheral surface of the barrel 22 and the outer peripheral surface of the plunger 24. The plunger 24 has
Motor holding member 67 and bearing housing 7
A rotary drive device such as a hydraulic motor 35 is connected via 1. Further, a sealing cylinder 22A is provided between the barrel 22 and the motor holding member 67 as a driving device for forward and backward movement. Further, an injection cylinder 72 and a piston rod 73 are attached between the motor holding member 67 and the support wall 20A. (The injection cylinder 72 may be attached to the barrel 22.) A convex portion 25 in contact with the inner peripheral surface of the barrel 22 is provided at the center of the plunger 24. Further, a screw 29 for discharging leaked material is provided on the rear side of the convex portion 25 of the plunger 24. This Skrill 29 is
The leak material leaking backward from the clearance between the outer peripheral surface of the convex portion 25 and the inner peripheral surface of the barrel 22 is
This is for smooth discharge to the rear of the barrel 22, and is provided in a threaded direction opposite to the direction of rotation of the plunger 24.

Reference numeral 27 denotes a staff provided perpendicularly to the material inlet 28 on the rear side of the barrel 22, and a staff plunger 30 for pushing down the material is provided inside the staff. Reference numeral 31 designates an inlet provided on the side surface of the staff 27 for supplying materials. Reference numeral 74 denotes a cylinder for the staff plunger 30, which is vertically attached to a portion of the staff 27 facing upward. 75 is a piston rod, and 76 is a connecting member.

The distal end portion of the plunger 24 is a conical tapered valve body 24a, and a valve body 24a is provided on the inner circumferential surface of the barrel 22 in a direction toward the distal end so as to engage with the tapered valve body 24a. A valve seat portion 22a is formed with a tapered portion that reduces in diameter. Note that the rear end of the sleeve 20 is also recessed into a conical shape, following the shape of the tip of the plunger.

In the device shown in FIG. 1, the barrel 22 is positioned at the forward limit, the plunger 24 is positioned so that the valve body portion 24a is separated from the valve seat portion 22a, and the plunger 24 is
While rotating at 100rpm, the Statshua 2
A material such as BMC is charged into the container 7, and the material is pushed down with a staff plunger 30. Then,
As shown in FIG. 2, the material is sent forward through the outer periphery of the plunger 24, and is passed through the valve seat portion 22a and the valve body portion 2.
4a, and are sequentially stored in the tip of the plunger 24 and the sleeve 20.

In this metering process, the barrel 22 gradually retreats. At this time, back pressure can be applied to the material by controlling the oil pressure of the injection cylinder 72 connected to the rear of the plunger 24.

Due to the rotation of the plunger 24, the plunger 24
The resin material around the material is homogenized, and the material flow path is prevented from shorting. Further, due to the pressing action of the staff plunger 30 and the rotation action of the plunger 24, the material does not pass only through the material passage 70 above the plunger 24, but also flows around to the material passage 70 below the plunger 24. In addition, the material is sent around the plunger 24 from the lower side to the upper side or from the upper side to the lower side. It is smoothly transferred around the entire circumference inside the barrel 22. Furthermore, since there is no member such as a check ring, damage to the glass fibers contained in the material is also reduced.

After a sufficient amount of material is measured into the tips of the sleeve 20 and barrel 22, the plunger 24 is advanced by the cylinder 22A, the valve body portion 24a is seated on the valve seat portion 22a, and the material in the sleeve 20 is withdrawn. cut off. Thereafter, the barrel 22 is advanced by the injection cylinder 72 via the motor holding member 67.
As a result, the material metered in the tip of the barrel 22 is pressed and flows into the sleeve 20, and is ejected from the nozzle 21 together with the material in the sleeve.

FIG. 3 is a sectional view of a main part of an injection molding machine according to a different embodiment.

In the embodiment shown in FIG. 3, the barrel 22 has a large diameter at its distal end, and a valve seat portion 22a whose diameter increases toward the distal end is provided in the middle of its inner peripheral surface. The tip of the plunger 24 is an enlarged head, and the proximal end of the enlarged head forms a valve body portion 24a whose diameter decreases toward the rear end of the plunger. Then, as shown in FIG. 4, when the sealing cylinder 22A is actuated to move the plunger 22 forward, the valve body 24a and the valve seat 22a are separated from each other, allowing the material to be fed toward the tip. becomes.
Also, on the contrary, the plunger 24 is moved backward and the valve body portion 2 is
When 4a is brought into close contact with the valve seat portion 22a, the metered material retreat path is blocked and injection becomes possible.

In this embodiment, the injection cylinder 72 is attached to the barrel 22, but its operation is performed at the first
It is similar to that shown, and the advancement of the barrel 22 causes injection of metered material. Further, during weighing, the barrel 22 is gradually retreated.

The rest of the structure and operation are the same as in FIG. 1, so the same members are given the same reference numerals and their explanations will be omitted.

5 and 6 each show a modification example of the installation of the valve seat portion 22a, in which the inner peripheral surface of the barrel 22 is reduced in diameter in an annular shape, and the slope of the reduced diameter portion is formed in the valve seat portion 22a.
That is.

FIG. 7 is a sectional view of a main part of an injection molding machine in which a preheating plunger 24b is provided at the tip of the plunger.
According to the preheating plunger 24b, it is possible to heat the material remaining in the sleeve 20, etc., and suppress an increase in its viscosity, thereby enabling a smoother injection molding machine.

In the present invention, the plunger may be of a screw type, or may be provided with some kind of protrusion or uneven structure. Also, the special application 1986-
A support as shown in 205352 may be provided to support the barrel on both sides to relieve bending stress on the plunger. Furthermore, various types of studs can be employed as long as they have a structure that has sufficient pressure supply capacity, such as a type that is pushed in with a plunger or a type that is pushed in with a screw.

[Effects] As is clear from the above examples, the injection molding machine of the present invention can open and close the material flow path without employing a check ring, etc., and prevents damage to glass fibers contained in the material. The effect is produced. Further, since metering is performed by moving the barrel backward, the length of the plunger in the axial direction may be small.

[Brief explanation of the drawing]

FIG. 1 is an overall sectional view of the embodiment device, FIG. 2 is a partial sectional view thereof, FIGS. 3, 4, 5, 6, and 7 are sectional views showing different embodiments. Figure 8,
9, 10 and 11 are cross-sectional views showing the prior art. 20...sleeve, 22...barrel, 24...
Plunger, 22a... valve seat portion, 24a... valve body portion, 30... staff plunger, 70... material passage.

Claims (1)

[Claims] 1. A barrel having a material inlet on the rear side, a sleeve fitted to the tip of the barrel so as to be slidable in the axial direction, and the tip of which serves as an injection port; is inserted and has a diameter that forms a material passage between its peripheral surface and the inner peripheral surface of the barrel,
and a plunger whose rear end side is connected to a drive device to be rotated; a valve seat portion provided in the middle of the barrel and consisting of an inner circumferential surface of the barrel whose diameter decreases toward the barrel tip; and a valve seat provided at the tip of the plunger. a valve body portion consisting of a plunger peripheral surface whose diameter decreases toward the tip of the plunger; and a plunger forward and backward movement device connected to the plunger for moving the valve seat portion and the valve body portion toward and away from each other. An injection molding machine comprising: a barrel back-and-forth movement device for material injection, which is connected to the barrel or the plunger. 2. A barrel having a material inlet on the rear side; a sleeve fitted to the tip of the barrel so as to be slidable in the axial direction; and the tip of the sleeve serving as an injection port; having a diameter that forms a material passage between the peripheral surface and the inner peripheral surface of the barrel;
and a plunger whose rear end side is connected to a drive device to be rotated; a valve seat provided in the middle of the barrel and consisting of an inner circumferential surface of the barrel that expands in diameter toward the tip of the barrel; and a valve seat provided at the tip of the plunger. a valve body portion consisting of a circumferential surface of the plunger whose diameter decreases toward the rear end of the plunger; and a forward and backward movement device for the plunger connected to the plunger for moving the valve seat portion toward and away from the valve body portion. An injection molding machine comprising: a barrel back and forth movement device for material injection, which is connected to the barrel.