JP3290119B2 - Pre-plastic injection molding machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pre-plastic injection molding machine having both a plasticizing device and an injection device for a resin, wherein the plasticized resin is measured and injected by an injection device.

[0002]

In a typical pre-plastic injection molding machine, a plasticizing cylinder is provided in parallel with an injection cylinder in which an injection plunger is removably mounted, and the injection cylinder and a plasticizing screw or plunger are used. The internal plasticizing cylinder communicates with a resin passage provided over the distal end, and the rear end of the shaft of the injection plunger is connected to the piston of a hydraulic cylinder behind the injection cylinder.

In order to reduce the sliding resistance when the injection plunger moves forward and backward, the inner peripheral wall of the injection cylinder is formed by a cylinder liner, while the shaft of the injection plunger is formed to have a small diameter except for the head. , A required clearance is formed between the head and the shaft and the cylinder liner.

Since the clearance around the shaft of the injection plunger is formed larger than the clearance around the head, it also serves as a clearance for removing the resin that has entered the clearance around the head. Is scraped out of the clearance by the trailing edge of the head, and further scraped from around the shaft by the scraping member and discharged out of the injection cylinder. For this reason, it is said that, even if the resin enters the clearance, as long as the resin does not solidify, the clearance is not filled up and the sliding resistance of the injection plunger does not occur.

[0005] Therefore, a study on the clearance has been repeated, and it has been found that if the material of the injection plunger and the cylinder liner are not the same, the clearance changes depending on the set temperature due to the difference in the coefficient of thermal expansion. For example, when the temperature is increased, the thermal expansion coefficient becomes: injection plunger> cylinder liner, clearance decreases. Injection plunger <cylinder liner, clearance increases. Injection plunger = cylinder liner, clearance does not change. In particular, the clearance around the head is very small, with a set value of 0.005 to 0.01 mm in radius, so if the clearance is small, the bite is likely to occur, and if the clearance is large, The amount of resin leakage from the clearance increases, and the measured amount of resin is lost during injection.

For this reason, it is desirable to use the same material for both materials. However, in the case of general steel materials, biting due to eccentricity due to heating and pressure, abrasion and corrosion due to resin, and adhesion to resin, etc. And the problem that it is difficult to use it as it is. This problem can be solved by using a boron alloy that is excellent in wear resistance and corrosion resistance and hardly adheres to the resin, but the boron alloy has a problem in workability and a problem in impact strength. In addition, there are new problems such as high cost and high cost.

The present invention was conceived in view of the above circumstances, and an object of the present invention is to solve the problems of a base material by using a hard material such as a boron alloy in combination with the base material even if the base material is a steel material. It is another object of the present invention to provide a new pre-plastic injection molding machine in which the movement of the injection plunger is smooth and resin leakage is reduced by suppressing the fluctuation of the clearance due to the coefficient of thermal expansion.

[0008]

SUMMARY OF THE INVENTION According to the present invention, there is provided an injection cylinder in which an injection plunger is reciprocally movable, a plasticizing cylinder is provided in parallel, and the injection cylinder and the plasticizing cylinder are provided over a tip portion. While communicating with the resin path, the inner peripheral wall of the injection cylinder is molded with a cylinder liner, the shaft of the injection plunger is formed with a small diameter except for the head, and a required clearance is provided between the shaft and the cylinder liner. The injection plunger and the base material of the cylinder liner are made of the same steel, and the surfaces thereof are made of the same hard material. It is formed in a hardened layer of 0.5 to 1.0 mm, and both thermal expansion coefficients are configured to be equal,
Further, the hardened layer is made of a boron alloy.

In such a configuration, the base materials are made of the same steel type, so that the coefficients of thermal expansion are equal, and the problems of the base materials are solved by a hardened layer made of a hard material such as a boron alloy which forms the surface. In addition, the injection plunger is excellent in abrasion resistance, and the sliding resistance of the injection plunger due to the adhesion of the resin is almost eliminated, and the injection plunger always moves smoothly even in long-term use, so that the pressure loss at the time of injection is small.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the drawings, reference numeral 1 denotes an injection device, 2 denotes a plasticizing device juxtaposed on the injection device, and both devices are connected to each other by a resin path 3 provided at the tip.

The injection apparatus 1 includes an injection cylinder 12 having an injection plunger 10 movable therein and retractable and having a nozzle 11 at the tip, a hydraulic cylinder 13 provided behind the injection cylinder 12, and a hydraulic cylinder 13. And a member 14 that fits and holds the rear end of the injection cylinder 12 integrally with the front part.

The inner peripheral wall of the injection cylinder 12 is formed by a cylinder liner 12a. The injection plunger 10 includes a head portion 10a at the tip and a shaft portion 10b formed with a smaller diameter than the head portion 10a. The rear end of the hydraulic cylinder 13 within the rear of the holding member 14
5 is connected to the tip. Further, a clearance 16 of 0.05 to 0.20 mm larger than the clearance around the head 10a is formed between the small diameter shaft portion 10b and the cylinder liner 12a forming the inner peripheral wall of the injection cylinder 12. When the injection plunger 10 moves forward, the resin that has entered the clearance around the head 10a adheres to the injection cylinder side of the clearance 16 and remains, and when the injection plunger 10 retreats, the resin is removed by the rear edge of the head. The liquid is sequentially sent to the rear of the injection cylinder 12, and is discharged from the rear end opening to the outside through the lower opening 14 a of the holding member 14. The resin adhering to the shaft is scraped off by the scraping member 4 and
is discharged from a.

The shaft 10b of the injection plunger 10
Bearing portion 14b behind opening 14a of holding member 14
A predetermined clearance is provided in a holding sleeve 18 that is inserted through the center of the holding sleeve 18, and the holding sleeve 18 is inserted and held.

The base materials of the injection plunger 10 and the cylinder liner 12a are of the same steel type, for example, SCM440 and SCM440.
It is formed of a steel material such as US 403 or SUS 630, and the surfaces thereof are formed as hardened layers 12c and 10c having a thickness of 0.5 to 1.0 mm made of a boron alloy so as to have the same coefficient of thermal expansion.

The plasticizing apparatus 2 comprises a plasticizing cylinder 22 having a plasticizing screw 20 rotatably mounted therein and having an outflow passage 21 at a front end, and a rear end holding the plasticizing cylinder 22. Although not shown in the drawing, the cylinder 23 includes a hydraulic cylinder for screw advance and retreat connected to the rear end of the holding cylinder 23, and a rotation driving device for the screw 20.

The resin passage 3 is provided with an inflow passage 17 provided at an upper end of the tip end of the injection cylinder 12 which corresponds to a plunger advance limit.
And a pipe slanted over the outflow passage 21 of the plasticizing device 2, and the screw 20 passes through the resin passage 3.
The plasticized (melted / kneaded) resin is supplied into the tip of the injection cylinder 12 by moving the injection plunger 10 backward. Reference numeral 19 denotes a band heater provided on the outer periphery of the cylinder and the outer periphery of the resin path.

As described above, according to the present invention, the base material and the surface of the injection plunger 10 and the cylinder liner 12a are formed on the hardened layers 12b and 10c of the same steel material and the same composition. equally,
For this reason, there is almost no fluctuation due to thermal expansion in the clearance 16 around the shaft portion, which is formed smaller than before, as well as the clearance at the head, so that the sliding resistance of the injection plunger 10 due to the fluctuation in the clearance is eliminated. Combined with the prevention of carbonization of the resin due to the reduction of the clearance setting value, the sliding resistance of the injection plunger is significantly reduced, and the injection plunger moves forward and backward without rubbing or biting even during long-time molding. Will always be done smoothly.

[Brief description of the drawings]

FIG. 1 is a partial longitudinal sectional view of a pre-plastic injection molding machine according to the present invention.

FIG. 2 is an enlarged view of a main part of the above.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 injection device 2 plasticizing device 3 resin path 4 scraping member 10 injection plunger 10a head 10b shaft portion 10c hardened layer 12 injection cylinder 12a cylinder liner 12b hardened layer 13 hydraulic cylinder 14 holding member 15 piston 16 clearance around shaft portion 22 Plasticizing cylinder

Claims (2)

(57) [Claims] A plasticizing cylinder is provided side by side with an injection cylinder in which an injection plunger is provided so as to be able to move forward and backward, and the injection cylinder and the plasticizing cylinder are communicated with each other by a resin path provided over a tip portion. The peripheral wall is formed by a cylinder liner, the shaft of the injection plunger is formed to have a small diameter except for the head, a required clearance is formed between the shaft and the cylinder liner, and the rear end of the shaft is rearward of the injection cylinder. In the pre-plastic injection molding machine connected to the piston of the hydraulic cylinder, the injection plunger and the base material of the cylinder liner are made of the same steel type, and the surfaces thereof are made of the same hard material with a thickness of 0.5 mm.
A pre-plastic injection molding machine characterized by forming a hardened layer having a thickness of about 1.0 mm and having the same coefficient of thermal expansion. 2. The pre-plastic injection molding machine according to claim 1, wherein said hardened layer is made of a boron alloy.