JPH053812B2 - - 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.

The present applicant has disclosed Japanese Patent Application No. 60-79197, No. 60-168898,
In No. 61-77309, we proposed a rotating plunger type injection molding machine.

In the injection molding machines according to these earlier applications, when the staff plunger for material supply is advanced while the plunger located at the front within the barrel of the injection cylinder is rotated, the material is metered and The material is supplied to the tip inside the barrel of the injection cylinder via the material passage and backflow prevention mechanism. Metering ends when the desired amount of BMC, etc. is accumulated in front of the barrel, and then when the plunger is moved forward, the material is injected from the nozzle, but in this case, the material that entered the material path first comes out first. Additionally, the rotation of the plunger makes the flow of material extremely smooth and uniform. This plunger type injection molding machine is
Although it does not have a part equivalent to a screw type flight, it has the characteristic that the metering capacity increases as the rotation speed increases.

[Problems to be solved by the invention] Japanese Patent Application No. 60-79197, No. 60-168898, No. 61-
According to the above structure proposed in 77309, a molded product with excellent performance can be obtained with less damage to the glass fibers, but it was recognized that this type has the following improvement issues. .

That is, in the injection molding machine of the prior application, the material is measured by the pressing action of the stuffer, so in order to improve the measuring ability, it is necessary to increase the pressure applied by the stuffer. Since the plunger is mechanically cantilevered and is installed so that the axis of the plunger and the axis of the stud are perpendicular to each other, increasing the stud pressure in this way causes the pressure to be generated on the plunger. The cantilever load (bending load) increases considerably, which is structurally unfavorable.

[Means for Solving the Problems] The injection molding machine of the present invention includes a barrel having an injection port at its tip, and a barrel connected at an angle rearward to the barrel for filling and injecting material into the barrel. The kneading shaft is rotatably inserted into the barrel about its axis and rotated by a drive device.

[Function] In the injection molding machine of the present invention, material is supplied into the staff. When the staff plunger moves forward, this material is forced into the barrel and is kneaded as the kneading shaft inside the barrel rotates. After completing the filling process by advancing the stuffing plunger so that the inside of the barrel is completely filled with the material, the stuffing plunger is further advanced to inject the material from the injection port at the tip of the barrel.

In the injection molding machine and injection according to the invention, the filling process (corresponding to the conventional metering process) is carried out exclusively by the advancement of the stuffing plunger, and the kneading shaft (corresponding to the conventional injection plunger)
is shorter than this conventional plunger.
Further, the pressing force from the studs on the kneading shaft is applied obliquely from the rear, and is different from the pressing force applied in the direction perpendicular to the axis as in the prior art. Therefore, the short length of this kneading shaft and the oblique pressing force from the studs result in a small cantilever load (bending load) on the kneading shaft, resulting in excellent durability. It becomes a structure.

[Examples] The present invention will be described in more detail below with reference to examples shown in the drawings.

FIG. 1 is a vertical cross-sectional view of a main part of an injection molding machine according to an embodiment of the present invention, and FIG. 2 is an overall side view.

First, the overall structure of the injection molding machine according to this embodiment will be explained with reference to FIG. Reference numeral 10 is a movable base on which a barrel 12 and a hydraulic motor 14 are installed. The barrel 12 has a nozzle portion 16 on its tip side, and the tip end serves as an injection port 18. A kneading shaft 20 is installed inside the barrel 12, and the rear end of the shaft 20 is connected to the hydraulic motor 14.

A stuffing device 24 is provided at the top of the barrel 12. This staff device includes a staff barrel 24, a staff plunger 26 inserted into the staff barrel 24, a hydraulic cylinder 28 attached to the staff barrel 24, a rod 28a of the hydraulic cylinder 28, and a staff plunger 26.
6 and a connector 30 for connecting the two. Further, a material input hopper 32 is attached to the side periphery of the stuffer barrel 24.

The movable base 10 is slidable in the longitudinal direction of the barrel 12 by a hydraulic cylinder (not shown), and is configured so that the nozzle portion 16 of the barrel 12 can be brought into contact with and separated from a mold (not shown).

As shown in an enlarged view in FIG.
A material input port 36 is provided on the side circumferential surface of 4.

The material kneading shaft 20 has a protrusion 38 at a rear portion of the opening 34, and the protrusion 38 is configured to slide on the inner peripheral surface of the barrel 12 with a slight clearance. . A flight 40 made of a spirally circulating protrusion is provided on the shaft 20 at a portion forward of the protrusion 38 . A screw 42 for discharging leakage material is provided behind the protrusion 38 and has a screw direction opposite to the screw direction of the flight 40.

The operation of the injection molding machine configured as described above will be explained next. First of all, the staff plunger 26
The hydraulic cylinder 28 is operated so that its lower end surface is above the input port 36, and injection material such as BMC is charged into the staff barrel 24 through the hopper 32 and the input port 36. The stuffing plunger 26 is then lowered to force the material into the barrel 12. Note that prior to this pushing, the kneading shaft 20 is rotated by driving the hydraulic motor 14. The material pushed into the barrel 12 is kneaded as the shaft 20 rotates, and is filled into the barrel 12 as the stuffing plunger 26 gradually descends.

The filling process is completed when the barrel 12 is completely filled with the material. Thereafter, the staff plunger 26 is further lowered by a predetermined stroke at a required pressure, and the material is injected from the injection port 18 to perform an injection process. After this injection process is completed, the staff plunger 26 is pushed up again to the standby position shown in FIG. 1, material is again introduced from the input port 36, and the filling process and injection process are performed in the same manner.

As described above, in the injection molding machine of the present invention, the kneading shaft 20 does not move forward or backward during either the filling or injection process, but rotates around its axis to only knead the materials. Therefore, unlike the plunger in the barrel of a conventional injection molding machine, there is no need to retract it during metering, and its axial length can be short. Further, the downward pressing force for lowering the staff plunger 26 acts on the shaft 20 from the rear obliquely in the axial direction, so that the shaft 20
The load is reduced until it is applied. For this reason, in the injection molding machine of the present invention, the cantilever load (bending load) applied to the kneading shaft 20 is reduced, resulting in excellent structural durability.

Note that the flights 40 increase the kneading efficiency of the materials supplied into the barrel 12 and also
It also functions to smoothly send the material fed from 4 forward into the barrel 12.

In this embodiment, the flights 40 made of protrusions are provided as described above, but in the present invention, the protrusions may be replaced by grooves. Moreover, these convex lines or concave lines may be omitted.

In the embodiment described above, since the front end surface of the protrusion 38 is made to coincide with the rear end of the opening 34, there is an effect that material is prevented from accumulating at the front end surface portion of the protrusion 38, which is indicated by A in the figure.

In addition, in the present invention, the receding angle θ (first
(see figure) is preferably about 5° to 50°, especially about 10° to 40°.

[Effects of the Invention] As described above, in the injection molding machine of the present invention, the bending load applied to the kneading shaft, which is mechanically cantilevered, is reduced, and the durability of this shaft is improved.

[Brief explanation of drawings]

FIG. 1 is a vertical cross-sectional view of a main part of an injection molding machine according to an embodiment of the present invention, and FIG. 2 is a side view showing the overall configuration of the injection molding machine. DESCRIPTION OF SYMBOLS 12... Barrel, 18... Injection port, 20... Shaft for kneading, 22... Staff device, 26... Staff member plunger, 40... Flight.

Claims (1)

[Scope of Claims] 1. A barrel having a material inlet on the rear side; a statue device for filling and injecting material into the barrel, which is connected at an angle inclined rearward to the barrel; and within the barrel. An injection molding machine comprising: a kneading shaft rotatably inserted around its axis and rotated by a drive device; 2. The injection molding machine according to claim 1, wherein the shaft for the kneading molding machine is provided with spiral protrusions or grooves.