JP2612087B2 - Injection molding machine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a screw-type injection molding machine.

(Prior art) Conventionally, a molding material heated and fluidized in a heating cylinder is injected into a mold by high pressure, cooled and solidified or hardened therein, and then the mold is opened to take out a molded product. There are two types of machines: a plunger type in which the plunger is moved forward and backward, and injection molding, and a screw type, in which the screw is moved forward and backward, and injection molding.The flanger type is compared with the screw type. A screw type is generally used because it is inferior in plasticizing ability of the material and has a large injection pressure loss.

The conventional injection molding machine will be described with reference to FIGS.

2 is a sectional view of a conventional injection molding machine, FIG. 3 is a state diagram of each step in the conventional injection molding machine, FIG. 3 (A) is a weighing state diagram, and FIG. 3 (B) is a weighing completed state. FIG. 3 (C) is an injection start state diagram, and FIG. 3 (D) is an injection state diagram.

In FIG. 2, a screw 2 is supported inside a heating cylinder 1 of an injection molding machine so as to be rotatable and forward and backward. That is, the screw 2 is connected to a drive system including an electric motor or a hydraulic motor (not shown), and is moved forward and backward by the drive system.

In the above-described injection molding machine, when the injection molding shot is completed, an operation of melting and plasticizing the molding material 5 and storing it at the tip of the screw head 3 prior to the next shot, that is, weighing is performed. In this measurement, the screw 2 is driven by the drive system and retreats. At this time, the molding material 5 dropped and supplied from the material supply port moves forward in the groove 6 by the rotation of the screw 2. It is melt-plasticized in the heating cylinder 1 and stored at the front end of the screw 2. The pressure of the molding material 5 in the heating cylinder 1 generated by the melt plasticization becomes a reaction force against the screw 2, and the screw 2 retreats due to the reaction force.

Thus, the molding material 5 stored at the front end of the screw 2 is subsequently injected into the mold from the nozzle 7 by pushing the screw 2 forward by the drive system.

Here, a part of the molding material 5 flows backward through the groove 6 of the screw 2 due to the reaction force of the injection force applied when the molding material 5 is injected into the mold. In order to prevent this, a backflow prevention ring 12 is provided at the front end of the screw 2. Then, the main body portion of the screw 2 and the screw head 3 are formed separately so that the backflow prevention ring 12 does not come off from the screw 2, and both are screwed.
An annular recess 8 is formed at the rear of the screw head 3, and the outer diameter of the screw head 3 is made larger than the inner diameter of the backflow prevention ring 12, so that the backflow prevention ring 12 does not come off.

The flow preventing ring 12 forms a flow path 13 for the molding material between the screw head 3 and the screw head 3. In the measuring step (FIG. 3 (A)) in which the screw 2 retreats, the flow path prevention ring 12 has the flow path 13. 13
The molding material is sent to the front of the screw 2 via. On the other hand, in the injection step (FIG. 3 (D)) in which the screw 2 moves forward, the backflow prevention ring 12 comes into contact with a seal ring 14 provided on the screw end face, so that the flow path is prevented.
13 is closed to prevent backflow of the molding material.

(Problems to be Solved by the Invention) However, in the above-mentioned conventional injection molding machine, when the measuring step shown in FIG. 3A is completed and the state shown in FIG. The ring 12 moves toward the screw head 3 and is in contact therewith, but as shown in FIG. 3 (C), a short time from the start of injection to the contact of the backflow prevention ring 12 with the seal ring 14. The molding material flows backward in the direction of the arrow.

During this time, the distance that the screw 2 moves is a short 5.0m
m, the long one has a variation of 20 mm, and the amount of the molding material injected differs due to the variation. Therefore, the molding becomes unstable and precision molding becomes difficult.

The present invention solves the above-described problems, prevents an injection material from flowing backward from the time of completion of injection measurement to the start of injection, and enables an injection molding machine capable of performing molding in a stable manner. The purpose is to provide.

(Means for Solving the Problems) For this purpose, in the injection molding machine of the present invention, a heating cylinder, a screw disposed in the heating cylinder so as to be able to move forward and backward, and rotatable, and formed at the tip of the screw. A screw head, an annular recess formed between the screw head and the screw, a seal ring formed on the screw side of the annular recess, and a backflow prevention slidably disposed in the annular recess in a forward and backward direction. A ring and driving means for moving the screw back and forth, wherein the driving means retracts the screw by a set distance between the completion of the metering step and the start of the injection step, and returns the screw to the metering completed position again to prevent backflow. Means are provided for bringing the ring into contact with the seal ring.

(Operation) According to the present invention, as described above, the heating cylinder, the screw disposed to be able to move forward and backward in the heating cylinder, and rotatable, and the screw head formed at the tip of the screw,
An annular recess formed between the screw head and the screw, a seal ring formed on the screw side of the annular recess, a backflow prevention ring slidably disposed back and forth in the annular recess, Between the completion of the weighing step and the start of the injection step, the drive means retreats the screw by a set distance, returns the screw to the weighing completed position again, and attaches the backflow prevention ring to the seal ring. Since the screw is provided with an abutting means, the screw can be advanced to start injection after the screw is retracted, and the backflow prevention ring can be abutted on the seal ring.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to FIG.

FIG. 1 is a state diagram of each step of the injection molding machine of the present invention.
FIG. 1A is a diagram showing a weighing state, FIG. 1B is a diagram showing a weighing completed state, FIG. 1C is a diagram showing a screw retracted state, and FIG.
Is an injection start state diagram.

In the measuring state shown in FIG. 1 (A), the screw 2 retreats while rotating as shown by the arrow M, and the melted resin proceeds through the flow path 13 formed in the screw head 3 as shown by the arrow N to form the screw 2. Collect at the tip. At this time, the backflow prevention ring 12 is in contact with the rear end face of the screw head 3 and the seal ring
Since a gap is formed between the molding material and the molding material 14, the molding material can move freely.

When the measuring step is completed and the state shown in FIG. 1 (B) is reached, the process proceeds to the injection step. In the injection molding machine of the present invention, the screw 2 is set once as shown in FIG. 1 (C). It is retracted by a distance l. The set distance is a distance sufficient for the backflow prevention ring 12 to move rearward and abut against the seal ring 14 when the screw 2 is once retracted and placed at the metering completion position.

That is, when the screw 2 is retracted by the distance 1 as shown in FIG. 1 (C), and then advanced as shown in FIG. 1 (D) and placed at the measurement completion position (the state shown in FIG. 1 (B)). The backflow prevention ring 12 contacts the rear seal ring 14.

Therefore, in the metering completed position, the backflow prevention ring
The space between the seal ring 12 and the seal ring 14 is completely sealed, so that when the injection is started, the molding material does not flow backward backward.

Therefore, by detecting the metering completion position, that is, the injection start position, it is possible to accurately perform the program control of the subsequent injection process.

It should be noted that the present invention is not limited to the above embodiment, and various modifications are possible based on the gist of the present invention.
They are not excluded from the scope of the present invention.

(Effects of the Invention) As described above, according to the present invention, a heating cylinder, a screw disposed to be able to move forward and backward in the heating cylinder and rotatable, and a screw head formed at a tip of the screw are provided. An annular recess formed between the screw head and the screw, a seal ring formed on the screw side of the annular recess, a backflow prevention ring slidably disposed back and forth in the annular recess, A driving unit for moving the screw back and forth, wherein the driving unit retracts the screw by a set distance between the completion of the metering process and the start of the injection process, returns the screw to the metering completion position again, and seals the backflow prevention ring with In the state where the screw is advanced to the metering completion position, the backflow prevention ring abuts on the seal ring to seal the gap between them. Therefore, the molding material does not flow backward after the start of the injection.

Therefore, the injection amount of the molding material in the injection step becomes constant, and the program control can be accurately performed.

[Brief description of the drawings]

FIG. 1 is a state diagram of each step of the injection molding machine of the present invention, FIG. 1 (A) is a weighing state diagram, FIG. 1 (B) is a weighing completed state diagram,
FIG. 1 (C) is a screw retreat state diagram, FIG. 1 (D) is an injection start state diagram, FIG. 2 is a sectional view of a conventional injection molding machine, and FIG. State diagram, third
3 (A) is a diagram showing a weighing state, FIG. 3 (B) is a diagram showing a completion state of weighing, FIG. 3 (C) is a diagram showing an injection start state, and FIG. 3 (D) is a diagram showing an injection state. DESCRIPTION OF SYMBOLS 1 ... Heating cylinder, 2 ... Screw, 3 ... Screw head, 12 ... Backflow prevention ring, 13 ... Flow path, 14 ... Seal ring.

Claims (1)

(57) [Claims] (A) a heating cylinder; (b) a screw disposed in the heating cylinder so as to be able to move forward and backward; and (c) a screw head formed at a tip of the screw. ) An annular recess formed between the screw head and the screw; (e) a seal ring formed on the screw side of the annular recess; and (f) slidably disposed in the annular recess. (G) driving means for moving the screw back and forth; (h) the driving means retreats the screw by a set distance between the completion of the metering step and the start of the injection step, and An injection molding machine comprising: means for returning a backflow prevention ring to a seal ring by returning to a measurement completion position.