JPS6235892B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a high injection pressure injection molding machine comprising a pressure cylinder, a pressure cylinder head attached to the tip of the pressure cylinder, and a screw inserted into a plastic chamber of the pressure cylinder. In particular, a small plasticizing chamber having a smaller diameter than the plasticizing chamber and a ram hole opening from the side into the small plasticizing chamber are formed in the pressure-resistant cylinder head continuously from the plasticizing chamber, and a high pressure is provided in the ram hole. This invention relates to a high injection pressure injection molding machine in which a ram is slidably and closely inserted.

As is well known, there are various types of injection molding machines that mold thermoplastic resin materials, and a screw inserted into a pressure cylinder rotates to plasticize the resin material while transferring it to the tip of the pressure cylinder. The screw itself retreats as resin material accumulates, and when a predetermined amount of plasticized resin is accumulated at the tip of the pressure tube, the screw is moved in the direction of the tip of the pressure tube by an appropriate injection power source such as an injection cylinder. The so-called plasticized resin is injected from the nozzle by sliding the screw into the nozzle and operating the screw as a ram.
In-line screw injection molding machines are well known.

In-line screw injection molding machines include those that have a check valve in the screw head, and those that do not have a check valve and are equipped with a smear-type screw head that has a small gap between it and the inner wall of the pressure cylinder. It is also known that there is.

In an in-line screw injection molding machine in which such a check valve is incorporated into the screw head, high injection pressure cannot be achieved due to the mechanical strength caused by the presence of the check valve. Furthermore, even in those equipped with a smear-type screw head without a check valve, as the screw advances during the injection process, a portion of the plasticized resin in the plasticization chamber is formed between the smear-type head and the plasticization chamber wall. Since it is configured to flow backward through a micro gap, it is also impossible to obtain high injection pressure, and in particular, it is not possible to sufficiently increase the injection pressure at the end of the injection stroke.
Only an injection pressure of ~2500 Kg/cm ² could be obtained.

In this way, conventional in-line injection molding machines cannot perform injection molding with high injection pressure, and in particular, because a sufficiently high injection pressure cannot be obtained at the end of the injection stroke, the molded product shrinks significantly after curing. However, it has the disadvantage that satisfactory dimensional and shape accuracy cannot be obtained, making precision injection molding, which has been increasingly demanded in recent years, extremely difficult.

The purpose of this invention is to form a small plasticizing chamber with a smaller diameter than the plasticizing chamber at the tip of the plasticizing chamber in the pressure cylinder, in view of the problems caused by the structural limitations of the in-line screw type injection molding machine based on the above-mentioned prior art. By adopting a configuration in which a high-pressure ram is inserted into a ram hole that opens from the side into the small plasticizing chamber, the above drawbacks can be eliminated and a high injection pressure of 3000 to 5000 kg/cm ² can be obtained in order to meet the above requirements. The purpose is to provide an excellent injection molding machine for high injection pressure.

The structure of the present invention in accordance with the above object is that in the injection process, the operation is similar to that of a conventional in-line screw type injection molding machine at the beginning and middle of the injection stroke, and at the end of the injection stroke, the plasticized resin is transferred to the small diameter of the tip of the plasticizing chamber. The gist of this system is to confine the small chamber in a small chamber and apply high pressure to the small chamber by operating a ram, thereby making it possible to obtain a very high injection pressure.

Next, an embodiment of the present invention will be described below based on the drawings from FIG. 1 onwards.

In the figure, reference numeral 1 denotes a pressure-resistant cylinder, and a pressure-resistant cylinder head 2 is attached to the tip thereof, and an injection nozzle 3 is bored in the pressure-resistant cylinder head 2. A plasticizing chamber 4 is formed inside the pressure cylinder 1, and a screw 5 is inserted into the plasticizing chamber 4 so as to be rotatable and vertically slidable. 6 is a screw head, and 7 is a mold. A small plasticizing chamber 8 having a smaller diameter than the plasticizing chamber 4 is formed in the pressure-resistant cylinder head 2 in succession to the plasticizing chamber 4, and the small plasticizing chamber 8 communicates with the injection nozzle 3. On the other hand, a ram hole 9 is bored in the pressure cylinder head 2 from the side, and the ram hole 9 opens into the small plastic chamber 8 from the side. Reference numeral 10 denotes a high-pressure ram, which is slidably and closely inserted into the ram hole 9, and the rear portion of the high-pressure ram 10 is housed within a high-pressure injection cylinder 11. In addition, 8a is a shoulder part of the small plasticization chamber 8, and M is a resin material.

In the above configuration, when performing injection molding work, the screw 5 is gradually advanced inside the pressure cylinder 1 by an injection power source (not shown) from the state shown in FIG. M is injected into the mold 7 through the injection nozzle 3 while being pressurized.

Then, at the end of the injection stroke, as shown in FIG. 2, the tip of the screw head 6 of the screw 5 collides with the shoulder 8a of the small plasticizing chamber 8, sealing the small plasticizing chamber 8.

Next, as shown in FIG. 3, the high pressure injection cylinder 11 is operated to advance the high pressure ram 10. Therefore, the resin material M sealed in the small plasticizing chamber 8 is rapidly pressurized and injected into the mold 7 at high pressure.

At this time, since the small plasticizing chamber 8 is sealed by the tip of the screw head 6, even if high pressure is applied, the resin material M in the small plasticizing chamber 8 will remain inside the upper plasticizing chamber 4. Therefore, in the case of a type in which a check valve is incorporated in the screw head 6, high pressure is not applied to the check valve, so there is no influence on mechanical strength. Even in the case of the smear type screw head type, the resin material does not flow out from the gap between the screw head and the complete wall of the plasticizing chamber 4, and there is no influence on the pressure rise.

The diameter ratio, volume, etc. of the small plasticizing chamber 8 to the plasticizing chamber 4 are appropriately determined depending on the properties of the resin material, the shape of the molded product, etc. Further, the diameter of the ram hole 9, the retracted position of the high-pressure ram 10, and the above-mentioned protrusion amount are selectively determined depending on the amount of high-pressure injection required at the end of the injection stroke.

For this purpose, it is preferable that the pressure-resistant cylinder head 2 forming the small plastic chamber 8 be detachable from the pressure-resistant cylinder 1 and have a structure that can be replaced depending on the resin material or product type. It is preferable that the structure is such that a threaded groove 2a formed on the outer circumferential surface of the upper end of the portion 2 is coaxially engaged with a threaded groove 1a formed on the inner circumferential surface of the lower end of the pressure cylinder 1. .

As described above, according to the present invention, in an in-line screw injection molding machine comprising a pressure cylinder and a screw inserted into a plasticizing chamber of the pressure cylinder,
A small plasticizing chamber having a smaller cross-sectional area than the plasticizing chamber is connected to the tip of the plasticizing chamber, a ram hole is opened from the side of the small plasticizing chamber, and a high-pressure ram is inserted into the ram hole. This has the excellent effect that the plasticized resin material can be confined within the small plasticizing chamber and high pressure can be applied thereto, thereby dramatically increasing the injection pressure.

Furthermore, since the generation of the high injection pressure is achieved at the end of the injection stroke, when the highest injection pressure is required during the injection process, there is an advantage that extremely efficient injection molding operations can be performed.

Furthermore, since the small plasticizing chamber is closed by colliding the tip of the screw head with the shoulder of the small plasticizing chamber, when high pressure is applied to the resin material in the small plasticizing chamber by the high pressure ram, However, the resin material does not flow into the plasticizing chamber above.

For this reason, in the case of a type in which a check valve is built into the screw head, high pressure does not act on the check valve, so there is no impact on mechanical strength problems; on the other hand,
Even in the case of the smear type screw head type, there is an advantage that the resin material does not flow out from the gap between the smear type screw head and the wall of the plasticizing chamber, and an effective pressure increase can be achieved.

In addition, the capacity of the small plastic chamber can be changed by replacing the pressure-resistant cylinder head, so you can freely select the optimal pressure characteristics for various resin materials and product shapes. Another advantage is that the injection amount under high injection pressure can be set to an optimum value very easily by adjusting the retracted position and forward protrusion amount of the high-pressure ram.

In addition, the structure for obtaining high injection pressure as described above is extremely simple, and it has the practical advantage of being able to be implemented with only slight modifications to conventional injection molding machines. Achieving this has the great advantage of improving the molding accuracy of molded products and making precision injection molding possible.

[Brief explanation of the drawing]

The figure shows an embodiment of the invention.
The figure shows a sectional view of the pressure cylinder from the beginning to the middle of the injection stroke, Figure 2 is a sectional view of the pressure cylinder just before the end of the injection stroke, and Figure 3 shows the pressure cylinder when high pressure is applied at the end of the injection stroke. FIG. 1...Pressure tube, 2...Pressure tube head, 3...Injection nozzle, 4...Plasticization chamber, 5...Screw, 6...
...screw head, 8...small plasticizing chamber, 9...ram hole, 10...ram for high pressure, 11...injection cylinder for high pressure, M...resin material.

Claims (1)

[Scope of Claims] 1 A pressure-resistant cylinder 1 having a plasticizing chamber 4 inside, a pressure-resistant cylinder head 2 attached to the tip of the pressure-resistant cylinder and having an injection nozzle 3 at the tip, a rotational and vertical movement inside the plasticizing chamber of the pressure-resistant cylinder. In a high injection pressure injection molding machine comprising a screw 5 slidably inserted, the pressure-resistant cylinder head has a small plasticizing chamber 8 that is continuous with the plasticizing chamber and has a smaller diameter than the plasticizing chamber, and a small plasticizing chamber 8 that is adjacent to the small plasticizing chamber. An injection molding machine for high injection pressure, characterized in that a ram hole 9 is formed which opens from the side, and a ram 10 for high pressure is slidably and closely inserted into the ram hole. 2. High injection pressure according to claim 1, characterized in that the pressure-resistant cylinder head 2 in which the small plastic chamber 8 is formed is removably screwed onto the tip of the pressure-resistant cylinder 1. injection molding machine.