JPH0737853Y2 - Backflow prevention device for injection molding machine - Google Patents

Description

[Detailed description of the device]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an in-line screw type injection molding machine for preventing backward flow of molten resin backward during injection operation of an injection screw.

[0002]

2. Description of the Related Art As a backflow prevention device for an injection molding machine, those shown in FIGS. 3 and 4 are conventionally known. That is,
The backflow prevention device of FIG. 3 includes an injection screw 2 which is inserted into a heating cylinder 1 so as to be rotatable in the circumferential direction and movable in the axial direction.
The screw head 3 is attached to the front end (the left end in FIG. 3) via a circular small-diameter shaft 4, and a cylindrical backflow prevention ring (valve) 5 is attached to the front and rear of the small-diameter shaft 4 in the heating cylinder 1. It is structured so that it can be inserted freely. In this backflow prevention device, when the injection screw 2 moves leftward in FIG. 3 and injects the molten resin from the nozzle 6, the backflow prevention ring 5 moves relatively rearward (rightward), and the rear end face 5a is brought into contact with the front end surface 2a of the injection screw 2 to prevent the backward flow of the molten resin, and when the injection screw 2 rotates to plasticize the resin and measure it in front of the screw head 3, a backflow prevention ring 5 moves relatively to the left and the injection screw 2
Away from the resin, freeing the resin to flow forward.

The backflow prevention ring 5 of the backflow prevention device of FIG. 4 has a claw 5b at its front end. The claw 5b is locked in the resin flow groove 3a formed in the screw head 3,
The backflow prevention ring 5 is rotated together with the screw head 3 and the injection screw 2. The other structure of this backflow prevention device is the same as that of the backflow prevention device of FIG.

[0004]

The backflow prevention ring 5 of the backflow prevention device of FIG. 3 is completely independent of the injection screw 2 and the screw head 3, and does not rotate together with the injection screw 2 and the like. Therefore, the outer diameter of the backflow prevention ring 5 is made as close as possible to the inner diameter of the heating cylinder 1, and the gap G between the inner peripheral surface of the heating cylinder 1 and the outer peripheral surface of the backflow prevention ring 5 is reduced. The backflow of resin through G can be reduced,
During the metering operation of the injection screw 2, the rear end surface 3b of the screw head 3 slides on the front end surface 5c of the backflow prevention ring 5 and gradually wears to change its shape.

Further, in the backflow prevention device of FIG. 4, since the backflow prevention ring 5 rotates in the circumferential direction together with the screw head 3 and the like, there is no inconvenience of the backflow prevention device of FIG. 3, but the backflow prevention ring. There is a problem that the inner peripheral surface of the heating cylinder 1 and the outer peripheral surface of the backflow prevention ring 5 are easily worn when the heating roller 5 contacts the heating cylinder 1. Even if the outer diameter of the backflow prevention ring 5 is reduced, when the resin has a high viscosity, the flow may cause the backflow prevention ring 5 to eccentrically move in the radial direction to contact the heating cylinder 1, and the gap G As the size increases, the backflow of resin increases.

According to the present invention, the backflow prevention ring, the screw head, and the heating cylinder do not come into contact with each other to be worn, and the gap between the heating cylinder and the backflow prevention ring is reduced to suppress the backflow of the resin passing therethrough. It is an object of the present invention to provide a backflow prevention device for an injection molding machine, which is capable of

[0007]

In order to achieve the above object, the present invention provides an injection screw having a screw head attached to a front end thereof through a circular small diameter shaft so as to be rotatable in a heating cylinder in a circumferential direction. and movably inserted in the axial direction, the portion of the small-diameter shaft within the heating cylinder, in contact with the injection screw to prevent backflow into the rear of the molten resin during the injection operation of the injection screw, also injection subscription Interview injection backflow prevention ring to free the flow of the resin of relatively moved to the injection screw to release less clear <br/> Yuheddo forward the metering operation the screw head side of the fitted movably back and forth In the backflow prevention device of the molding machine, in the above-mentioned backflow prevention ring , the center bearing hole
Providing a bearing part with a through hole around which molten material flows
In addition, a pawl is provided at the front end, the backflow prevention ring is inserted into the bearing hole to stop the radial movement , and the pawl is melted on the screw head.
The structure is such that it is provided so as to be locked in the material flow channel .

[0008]

In the backflow prevention ring, the small diameter shaft is inserted through the bearing hole to stop the radial movement of the ring. Therefore, even if a radial force is applied by the flow of the molten material, the backflow prevention ring does not touch the heating cylinder. Therefore, the heating cylinder and the backflow prevention ring do not wear due to contact, and the gap between the heating cylinder and the backflow prevention ring can be reduced to reduce the backflow of the molten material through that portion. Furthermore, the backflow prevention ring is distributed
Together with the screw head, the claws locked in the groove
As it rotates, place it between the screw head and the backflow prevention ring.
Even if it does not wear.

[0009]

1 and 2 show an embodiment of the present invention. In addition, since the basic structure and operation of the backflow prevention device of FIGS. 1 and 2 are the same as those of the conventional backflow prevention device of FIGS. 3 and 4, the same reference numerals are given to corresponding parts. The detailed description is omitted.

The backflow prevention ring 5 has a bearing portion 5e at the center thereof. Circular shape at the center of bearing 5e (backflow prevention ring 5)
Bearing hole 5d is formed, and a plurality of (four in the figure) through holes 5f are formed around the bearing hole 5d. Also, the reverse
The flow prevention ring 5 has a claw 5b at its front end. The backflow prevention ring 5, Sukuryuhe the Rutotomoni claw 5b stopped the movement of the half-<br/> radially by inserting the small-diameter shaft 4 in the bearing hole 5d
It is attached to the small diameter shaft 4 slidably in the axial direction of the small diameter shaft 4 while being locked in the resin flow groove 3a formed in the pad 3 . The resin is circulated through the through holes 5f.

In the backflow prevention device of the injection molding machine according to the present invention having the above-mentioned structure, the backflow prevention ring 5 slides rearward along the small diameter shaft 4 at the time of the injection operation of the injection screw 2, and its rear end face. 5a is brought into contact with the front end surface 2a of the injection screw 2 to prevent backflow of the resin. Further, during the metering operation of the injection screw 2, the backflow prevention ring 5 slides forward along the small diameter shaft 4 and separates from the injection screw while rotating together with the screw head 3. The resin plasticized by the rotation of the injection screw 2 passes through the through hole 5 of the backflow prevention ring 5.
Flows in the front of the screw head 3 through f and the flow groove 3a of the screw head 3, and is measured.

In the above, even if a radial force is applied to the backflow prevention ring 5 by the resin flow, the backflow prevention ring 5
Does not move in the radial direction and contact the heating cylinder 1.
Therefore, it is possible to prevent wear due to contact between the heating cylinder 1 and the backflow prevention ring 5, and to further reduce the gap G between the heating cylinder 1 and the backflow prevention ring 5 to reduce resin backflow in that portion. it can. The backflow prevention ring 5 rotates together with the screw head 3 by the action of the claw 5b,
It goes without saying that no wear occurs between the screw head 3 and the backflow prevention ring 5. The through holes 5f may have a circular shape, and the shape and the number thereof are not limited to those shown in the figures and may be arbitrary.

[0013]

Since the backflow prevention device of the injection molding machine according to the present invention has the above-mentioned structure, the backflow prevention ring is eccentrically moved in the radial direction to touch the heating cylinder and contact the screw head to mutually contact each other. Will not wear out. Further, since the backflow prevention ring is always located at the center of the heating cylinder and keeps the clearance between the heating cylinder and the heating cylinder at the set value, there is an effect that the clearance can be reduced to reduce the reverse flow rate of the resin passing through the clearance. Furthermore,
The backflow prevention ring works by the action of the pawls that are locked in the flow groove.
Since it rotates with the screw head,
No wear occurs between the backflow prevention rings.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an embodiment of a backflow prevention device of an injection molding machine according to the present invention.

FIG. 2 is a sectional view taken along line (II-II) in FIG.

FIG. 3 is a cross-sectional view of a conventional backflow prevention device.

FIG. 4 is a cross-sectional view of another conventional backflow prevention device.

[Explanation of symbols]

1 Heating Cylinder 2 Injection Screw 3 Screw Head 3a Flow Groove 4 Small Diameter Shaft 5 Backflow Prevention Ring 5b Claw 5d Bearing Hole 5e Bearing 5f Through Hole

Claims (1)

[Scope of utility model registration request] 1. An injection screw having a screw head attached to a front end thereof through a circular small-diameter shaft is inserted into a heating cylinder so as to be rotatable in the circumferential direction and axially movable, and to be inserted into the heating cylinder. the portion of the small diameter shaft, abuts on the injection screw to prevent backflow into the rear of the molten resin during the injection operation of the injection screw, and from the injection screw moves relative to the screw head side in the metering operation of the injection subscription Interview in backflow prevention device for an injection molding machine backflow prevention ring to free is fitted movably in the back and forth flow of the resin to release less Cru head forward, the backflow prevention ring circumference of the bearing hole in the center
It has a bearing part in which the through hole through which the molten material flows is formed
Has a pawl at the front end with, it stopped radial movement by inserting the small-diameter shaft into the bearing hole, and the said pawl
Locked in the molten material flow channel formed on the screw head.
Backflow prevention device for an injection molding machine was characterized by provided.