JP2777486B2 - Backflow prevention device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backflow prevention device.

[0002]

2. Description of the Related Art Conventionally, a resin heated and fluidized in a heating cylinder is injected into a mold at high pressure, cooled therein, solidified or hardened, and then the mold is opened to take out a molded product. There are two types of injection molding machines: a plunger type that moves the plunger back and forth for injection molding, and a screw type that moves the screw back and forth for injection molding.
The plunger type is generally used because the plasticizing ability of the resin is inferior to the screw type, and the injection pressure loss is large.

FIG. 2 is a sectional view of a principal part of a screw head of a conventional injection molding machine, FIG. 3 is a plan view of a conventional backflow prevention device, and FIG. 4 is a sectional view of a principal part of a conventional backflow prevention device. In FIG. 2, a screw 2 is provided inside a heating cylinder 1 of an injection molding machine.
Are arranged rotatably and freely forward and backward. Here, the screw 2 is in a state where the injection molding shot has been completed, but prior to the next injection molding shot, an operation of melting and plasticizing the resin and storing it at the tip of the screw head 9, that is, weighing is performed. In the measuring step, the screw 2 is driven by a drive system (not shown) and retreats. At this time, the resin dropped and supplied from the material supply port is heated while moving forward in the groove 3 by the rotation of the screw 2. Cylinder 1
And is stored at the tip of the screw head 9.
The pressure of the resin in the heating cylinder 1 generated due to the melting is:
The reaction force acts on the screw 2, and the screw 2 moves backward by the reaction force.

[0004] The resin stored at the tip of the screw head 9 is then injected into the mold from the nozzle 4 by pushing the screw 2 forward by the drive system. Here, a part of the resin flows backward through the groove 3 of the screw 2 due to the reaction force of the injection force applied when the resin is injected into the mold. In order to prevent this, a check ring 6 is provided in front of the screw 2. Then, the main body 8 of the screw 2 and the screw head 9 are formed separately so that the check ring 6 does not come off from the screw 2, and both are screwed together by the screw portion 14. The screw head 9 has a large-diameter portion 9a and a small-diameter portion 9b. The outer diameter of the large-diameter portion 9a is larger than the inner diameter of the check ring 6 so that the check ring 6 does not come off.

The check ring 6 forms an annular flow path 10 between the check ring 6 and the small-diameter portion 9b of the screw head 9, and in the measuring step in which the screw 2 is retracted, the flow path 10
The resin is sent to the distal end of the screw head 9 via. On the other hand, in the injection step in which the screw 2 moves forward, the check ring 6 comes into contact with the seal ring 11 provided on the end face of the screw 2 to close the flow path 10 and prevent the resin from flowing backward. .

3 and 4, locking grooves 12 are provided at two locations in the circumferential direction of the large diameter portion 9a of the screw head 9.
Is formed, while the front end of the check ring 6 is formed in the circumferential direction 2.
A claw 15 is formed at a location, and the claw 15 is locked in the locking groove 12. Therefore, when the screw 2 (see FIG. 2) rotates in the measuring step, the check ring 6 also rotates, so that it is possible to prevent the occurrence of friction between the large diameter portion 9a and the front end of the check ring 6. .

[0007] At the front end of the check ring 6, two projections 16 are provided in the circumferential direction between the claws 15 so that the large diameter portion 9a and the front end of the check ring 6 are formed by the protrusions 16. A gap 17 is formed between them. The gap 17
Is an outlet for the resin flowing through the flow path 10 (see FIG. 2) during the measuring step.

[0008]

However, the above-mentioned conventional backflow prevention device is closed by receiving a frictional force between the check ring 6 and the heating cylinder 1, a resistance of the resin, a pressure difference between the front and rear of the check ring 6, and the like. As a result, differences in the closing behavior occur due to differences in resin and conditions, and the amount of resin flowing back changes, affecting the amount of cushion, not only changing the weight of the molded product but also forming The quality of the product is reduced.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems of the conventional backflow prevention device and to provide a backflow prevention device capable of improving the quality without changing the weight of a molded product. .

[0010]

For this purpose, in the backflow prevention device according to the present invention, a screw disposed in a heating cylinder, a driving system for moving the screw forward and backward and rotating the screw, and a tip end of the screw are provided. It has a large-diameter portion with a locking groove formed at the rear end and a screw head having a small-diameter portion.

[0011] Further, there is provided a check ring provided with a claw formed so as to surround the small diameter portion and corresponding to the locking groove.

After the measuring step is completed, the drive system rotates the screw in a predetermined direction to lock the claw and the locking groove, and generates an axial force to generate the check. A retracting means for retracting the ring, and a position restricting means for restricting the position of the screw in the axial direction while the check ring is retracted by the retracting means.

[0013]

According to the present invention, in the backflow prevention device as described above, a screw disposed in a heating cylinder, a drive system for moving the screw forward and backward and rotating, and a screw attached to the tip of the screw. And a screw head having a large diameter portion having a locking groove formed at the rear end and a small diameter portion.

[0014] Further, there is provided a check ring provided with a claw formed so as to surround the small diameter portion and corresponding to the locking groove.

After the measuring step is completed, the driving system rotates the screw in a predetermined direction to lock the claw and the locking groove, and generates an axial force to generate the check. A retracting means for retracting the ring, and a position restricting means for restricting the position of the screw in the axial direction while the check ring is retracted by the retracting means.

In this case, during the injection step, the check ring is retracted and abuts on the seal ring to prevent the resin from flowing backward. Also, during the weighing process,
The resin supplied between the screw and the heating cylinder is moved to the tip of the screw head and accumulated by the check ring being advanced.

When the measuring step is completed, the driving system is driven, the screw is rotated in a predetermined direction, the claw and the locking groove are locked, and an axial force is generated to generate the axial force. The check ring is retracted. Then, while the check ring is retracted, the position of the screw in the axial direction is restricted.

[0018]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a state diagram of the backflow prevention device of the present invention at the time of a measuring process, FIG. 5 is a state diagram of the backflow prevention device of the present invention during closing operation, and FIG. 6 is a load state diagram of the backflow prevention device of the present invention at the time of closing. It is.

In FIG. 1, reference numeral 6 denotes a check ring, reference numeral 9 denotes a screw head, reference numeral 11 denotes a seal ring disposed opposite to the rear end of the check ring 6, and reference numeral 12 denotes the screw head 9.
Are locking grooves formed at two locations in the circumferential direction of the large-diameter portion 9a. Therefore, when the screw 2 (see FIG. 2) rotates in the measuring step, the check ring 6 also rotates, so that friction occurs due to sliding between the large-diameter portion 9a and the front end of the check ring 6, resulting in resin burning. Can be prevented.

Claws 21 are formed at two positions in the circumferential direction corresponding to the locking grooves 12 at the front end of the check ring 6 so as to be locked by the locking grooves 12. A projection 16 is formed on the substrate. The large diameter portion 9 is formed by the projection 16.
A gap 17 is formed between a and the front end of the check ring 6. The gap 17 serves as an outlet for the resin flowing through the flow path 10 (see FIG. 2) during the measuring step.

Here, the locking groove 12 is formed in the large diameter portion 9a of the screw head 9 so as to extend forward from the rear end and to have a length sufficient to lock the claw 21. I have. The locking groove 12 has surfaces 12a and 12b facing each other. On the other hand, the claw 21
Has an engaging surface 21a extending in the axial direction of the screw 2 on the side facing the surface 12a, and a tapered surface 21b inclined on the axial direction of the screw 2 on the side facing the surface 12b. Therefore, during the weighing process, the screw 2
When the screw head 9 rotates in the direction of arrow A in FIG. 1, the locking surface 21 a comes into contact with the surface 12 a of the locking groove 12 to prevent the rotation of the check ring 6.

When the measuring step is completed, the screw 2 and the screw head 9 are reversely rotated by a predetermined amount in the direction of arrow B as shown in FIG. 5 in preparation for the next injection step. At this time, the tapered surface 21 of the claw 21 of the check ring 6
The rear end corner Q of the locking groove 12 on the surface 12b side abuts on the groove b.
At this time, a load F (FIG. 6) is applied in a direction perpendicular to the tapered surface 21b.
) Is applied, the check ring 6 rotates by the circumferential component force Fa of the load F, and moves backward by the axial component force Fb. As a result, the rear end of the check ring 6 comes into contact with the seal ring 11 to seal the gap therebetween, thereby preventing the resin from flowing backward.

As described above, in the backflow prevention device of the present invention, when the measuring step is completed, the screw 2 is reversely rotated by a predetermined amount, and the check ring 6 is brought into contact with the seal ring 11 for sealing. . In this case, it is sufficient that the check ring 6 is reversely rotated by an amount sufficient for the check ring 6 to abut on the seal ring 11 by the axial component Fb of the load F. By the way, when the screw 2 is rotated in reverse to bring the check ring 6 into contact with the seal ring 11, the screw 2 tends to advance in the direction opposite to that during the measuring step, that is, in the injection direction. Therefore, in order to stop the screw 2 at the metering completion position, the drive system of the screw 2 is operated, and the screw 2 is restrained from moving forward during this time. For example, when the drive system of the screw 2 is constituted by an injection cylinder, the hydraulic pressure is controlled to stop the screw 2 at the metering completion position.

The present invention is not limited to the above embodiment, but can be variously modified based on the gist of the present invention, and these are not excluded from the scope of the present invention.

[0025]

As described above in detail, according to the present invention, in the backflow prevention device, a screw disposed in a heating cylinder, a drive system for moving the screw back and forth, and rotating, A screw head provided with a large-diameter portion having a locking groove formed at the rear end and a locking portion formed at the rear end, and a screw head having the small-diameter portion, and arranged to surround the small-diameter portion and correspond to the locking groove. A check ring with a formed claw.

After the measuring step is completed, the drive system locks the claw and the locking groove by rotating the screw in a predetermined direction, and generates an axial force to generate the check. A retracting means for retracting the ring, and a position restricting means for restricting the position of the screw in the axial direction while the check ring is retracted by the retracting means.

In this case, when the measuring step is completed, the screw is rotated in a predetermined direction, and the check ring is retracted. Therefore, the check ring and the seal ring can be brought into contact with each other at the measurement completion position, so that when the injection process is started, the space between the check ring and the seal ring is sealed, thereby preventing the resin from flowing backward. can do. Also, while the check ring is being retracted, the screw attempts to move forward with the rotation, but since the position of the screw in the axial direction is restricted by the position restricting means, the screw is placed at the metering completion position. Will be left behind. Therefore, since a fixed amount can always be measured, the weight of the molded article does not change, and the quality can be improved.

[Brief description of the drawings]

FIG. 1 is a state diagram of a backflow prevention device according to the present invention during a measuring step.

FIG. 2 is a sectional view of a main part of a screw head of a conventional injection molding machine.

FIG. 3 is a plan view of a conventional backflow prevention device.

FIG. 4 is a sectional view of a main part of a conventional backflow prevention device.

FIG. 5 is a state diagram of the backflow prevention device according to the present invention at the time of a closing operation.

FIG. 6 is a load state diagram when the backflow prevention device of the present invention is closed.

[Explanation of symbols]

 2 Screw 6 Check ring 9 Screw head 9a Large diameter portion 9b Small diameter portion 11 Seal ring 12 Lock groove 12a, 12b surface 16 Projection 17 Gap 21 Claw 21a Lock surface 21b Tapered surface

Claims (1)

(57) [Claims] And 1. A (a) disk disposed within the heating cylinder <br/> Ryu, (b) the screw is the forward-reverse, and a drive system for rotating, mounted et the distal end of (c) above screw And locked at the rear end
Large-diameter portion in which the groove is formed, and a screw head with a small-diameter portion is disposed to surround (d) is the small-diameter portion, pair the locking groove
When having a check ring with claws formed by response
Both, (e) the drive system, after the metering step is completed, the pawl and the locking by rotating the screw in a predetermined direction
Locks the check ring with the groove.
Retraction means for reversing the clutch, and a check made by the retraction means
While it is allowed to ring retracts, the backflow prevention device according to claim Rukoto includes a position restraining means for restraining the position of the disk <br/> Ryu in the axial direction.