JPS63194915A - Injection molder - Google Patents

Abstract

PURPOSE:To reduce the bending load applied to a kneading shaft and consequently improve its durability by a structure wherein a stuffer device, which is connected to a barrel at an inclined angle and used for filling and injecting material, and the kneading shaft, which is inserted in the barrel so as to be freely rotatable about its axis center are provided. CONSTITUTION:An opening 34 to receive material is provided to a barrel 12. A charging port 36 of material is bored on the side peripheral surface of a stuffer barrel 24. A projected part 38, which slides onto the inner peripheral surface of the barrel 12 with a slight clearance between the part 38 and the barrel 12, is arranged onto a kneading shaft 20 at a part behind the opening 34. A flight 40 consisting of a spiral projecting strip is provided on the shaft at the forward side from the projected part 38, at the backward side from which a screw 42 for leaked material discharging, the helix angle of which is reverse to that of the flight 40, is provided. The pressing force during the lowering of a stuffer plunger 26 is applied to the shaft 20 from backward obliquely to the direction of the axis center line of the shaft 20, resulting in reducing the load given to the shaft 20. Since the cantilever load given to the kneading shaft 20 becomes smaller, the durability of the shaft is improved.

Description

[Detailed Description of the Invention] [Field of Application in Industry A] 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 C: compound.

[Prior art] Molding materials made by mixing glass fiber with synthetic resins such as unsaturated polyester have various compositions and compositions depending on the application and molding method.
There are properties.

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 proposed a rotary plunger type injection molding machine in Japanese Patent Application Nos. 60-79197, 60-168898, and 61-77309 as an injection molding machine suitable for such molding.

In the injection molding machines according to these earlier applications, when the stuffer plunger for material supply is advanced while the plunger located at the front in the barrel of the injection cylinder is rotated, the material is metered out at the material supply port. 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 a 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 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] Japanese Patent Application No. 60-79197, No. 6G-168898,
According to the above-mentioned structure proposed in 61-77309, a molded product with excellent performance can be obtained with less damage to the glass fibers, but this type has the following improvement issues. Admitted.

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 pressing pressure of the stuffer. Since the brassiere is mechanically cantilevered and is installed so that the axial direction of the plunger and the axial center of the stuffer are perpendicular to each other, increasing the stuffer pressure in this way causes the plunger to The cantilever load (bending load) generated on the structure 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 inclined backward with respect to the barrel.
The present invention includes a stuffer device for filling and injecting materials into a barrel, and a kneading shaft that is rotatably inserted into the barrel about its axis and rotated by a drive device.

[Operation] In the injection molding machine of the present invention, the material is fed into the stuffer. When the stuffer 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 stuffer plunger so that the inside of the barrel is completely filled with material, the stuffer 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 of the present invention, the filling process (corresponding to the conventional metering process) is carried out exclusively by the advancement of the stuffer plunger, and the mixing shaft (corresponding to the conventional injection plunger) It is shorter than a conventional plunger. Further, the pressing force from the stuffer on the kneading shaft is applied from an oblique rear direction, which is different from the conventional pressure applied in a direction perpendicular to the axis. Therefore, the combination of the short length of this kneading shaft and the fact that the pressing force from the stuffer is oblique,
The cantilever load (bending load) of the kneading shaft is reduced, resulting in a structure with excellent durability.

[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 part 16 at its tip side, and the most extreme part 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 stuffer device 22 is provided at the top of the barrel 12. This stuffer device includes a stuffer barrel 24, a stuffer plunger 26 inserted into the stuffer barrel 24, a hydraulic cylinder 28 attached to the stuffer 7 parel 24, a rod 28a of the hydraulic cylinder 28, and the stuffer plunger 26. It is configured to include a coupler 30 for connection. 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 to allow the nozzle portion 16 of the barrel 12 to approach and separate from a mold (not shown).

As shown in an enlarged view in FIG. 1, an opening 34 for receiving material from the stuffer is provided in the middle of the upper surface of the barrel 12, and a material input port is provided on the side peripheral surface of the stuffer 7 pallet 24. 36 have been established.

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 circumferential surface of the barrel 12 with a slight clearance. A portion of the shaft 20 on the front side of the protrusion 38
is provided with a flight 40 consisting of a protrusion that circulates in a spiral manner. Further, behind the protrusion 38, a screw 5.42 for discharging leakage material is provided in a direction opposite to the direction of the flight 40.

The operation of the injection molding machine configured as described above will be explained next. First, insert the stuffer plunger 26 into the hydraulic cylinder 28 so that its lower end surface is above the input port 36.
is operated, and injection material such as BMC is charged into the stuffer barrel 24 through the hopper 32 and the input port 36. The stuffer plunger 26 is then lowered to force this 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 the material is filled into the barrel 12 as the stuffer plunger 26 gradually descends.

The filling process is completed when the barrel 12 is completely filled with the material. After that, stuffer plunger 2
6 is further lowered by a predetermined stroke at a required pressure, the material is injected from the injection port 18, and an injection process is performed. After this injection process is completed, the stuffer 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 pressing force when lowering the stuffer plunger 26 acts on the shaft 20 from the obliquely rear side in the axial direction, and the load is reduced until it is applied to the shaft 20. 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 have the function of increasing the kneading efficiency of the material supplied into the barrel 12, and also have the function of smoothly sending the material fed through the opening 34 forward into the barrel 12.

In this embodiment, the flights 40 are formed of protrusions as described above, but in the present invention, grooves may be used instead of the protrusions. 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, the effect of preventing material from accumulating at the front end surface portion of the protrusion 38 indicated by A in the figure is enhanced.

In addition, in the present invention, the receding angle θ (see Fig. 1) between the axial direction of the stuffer device and the axial direction of the barrel is 5°.
-50°, especially about 10°-40° is suitable.

[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 the drawing]

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. 12... Barrel, 18... Injection port, 20
... Kneading shaft, 22 Statsfur device, 26...
・Staffer plunger, 40...flight.

Claims (2)

[Claims] (1) A barrel having a material inlet on the rear side, a stuffer device for filling and injecting material into the barrel, connected to the barrel at an angle inclined backward; An injection molding machine comprising: a kneading shaft inserted rotatably around an 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 a spiral protrusion or groove.