JP2556248B2 - Backflow prevention device for 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 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, the one shown in FIG. 7 is conventionally known. That is, this backflow prevention device is provided with a plurality of flow grooves on the outer peripheral surface at the front end (left end in FIG. 7) of the injection screw 2 which is inserted into the heating cylinder 1 so as to be rotatable in the circumferential direction and movable in the axial direction. The screw head 3 formed with 3a is attached via a circular small-diameter shaft 4, and a cylindrical backflow prevention ring (valve) 5 is movably fitted in the small-diameter shaft 4 in the heating cylinder 1 so as to be movable back and forth. It is said to have a different structure.

In this backflow prevention device, the backflow prevention ring 5 is provided when the injection screw 2 advances to the left in FIG. 7 and injects the molten resin from the nozzle 6 (hereinafter referred to as "injection operation"). It moves relatively to the rear (to the right), and the rear end surface 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 to the rear.

Further, when the injection screw 2 rotates to plasticize the resin and to measure it in front of the screw head 3 (hereinafter, abbreviated as a measuring operation), the backflow prevention ring 5 is used.
Moves relatively to the left away from the injection screw 2,
The front end surface 5b comes into contact with the rear end surface 3b of the screw head 3, thereby freeing the resin to flow forward.

[0005]

By the way, during the metering operation of the injection screw 2, the contact portion A between the screw head 3 and the backflow prevention ring 5 (the contact portion between the rear end face 3b and the front end face 5b) is the screw. The head 3 slides as it rotates. Therefore, when the contact area of the contact portion A is small, the contact surface pressure becomes high, and the wear of the contact portion A and the heating cylinder 1
Scratching may occur on the inner surface.

Therefore, a backflow prevention ring has already been developed which sufficiently increases the contact area of the contact portion A to prevent wear and galling.

However, if the contact area of the contact portion A is increased too much, the backflow prevention ring 5 is immediately released from the screw head 3 during the injection operation of the injection screw 2.
Does not separate, and the resin backflow prevention operation becomes slower (seal response becomes worse). If the seal responsiveness of the backflow prevention ring 5 is deteriorated, short-circuits, burrs, variations in weight and dimensions, etc. occur in the molded product, which adversely affects it. As described above, the conventional backflow prevention ring 5 cannot simultaneously solve the problems of wear and galling during the metering operation and the improvement of the seal responsiveness of the resin backflow prevention during the injection operation.

The present invention provides a backflow prevention device for an injection molding machine, which prevents wear and galling during the metering operation of the injection screw, and enhances the seal response during the injection operation of the injection screw to reliably prevent resin backflow. The purpose is to provide.

[0009]

In order to achieve the above object, a backflow preventer for an injection molding machine according to claim 1 of the present invention is an injection machine in which a screw head is attached to a front end through a circular small diameter shaft. The screw is inserted into the heating cylinder so as to be rotatable in the circumferential direction and movable in the axial direction, and comes into contact with the injection screw at the time of injection operation of the injection screw into the portion of the small diameter shaft in the heating cylinder so that the molten resin A cylindrical backflow prevention ring that prevents backflow to the rear and that moves to the screw head side relative to the screw head when the injection screw is metered to allow free flow of resin to the front of the screw head is movably fitted back and forth. In the backflow prevention device of the inserted injection molding machine, the backflow prevention ring includes a first backflow prevention ring having a front end surface slidably contacting a rear end surface of the screw head, and a backflow prevention ring slidable with the rear end surface of the first backflow prevention ring. Freely And a second backflow prevention ring having a rear end surface abutting against the front end surface of the injection screw. The contact portion between the screw head and the first backflow prevention ring has the contact area described above. The contact area between the first backflow prevention ring and the second backflow prevention ring is smaller than the contact area, and the contact area is small.

According to a second aspect of the present invention, there is provided a backflow prevention device for an injection molding machine according to the first aspect, wherein the rear end surface and the front end surface of the first backflow prevention ring are slidably in contact with each other. Instead of the ring, the second backflow prevention ring rotates integrally with the first backflow prevention ring by engagement with the rear end surface of the first backflow prevention ring, and allows the relative movement with the first backflow prevention ring in the axial direction.
The backflow prevention ring is provided, and the contact area of the engaging portion between the first backflow prevention ring and the second backflow prevention ring is smaller than the contact area between the screw head and the first backflow prevention ring. It has a structure.

[0011]

According to the backflow prevention device for an injection molding machine according to the first aspect of the present invention, the first backflow prevention ring rotates together with the rotation of the screw head during the metering operation of the injection screw. A certain first backflow prevention ring rotates at a lower speed than the screw head due to the viscous resistance of the resin.
The contact portion between the first backflow prevention ring and the screw head slides, but since the contact area of the contact portion is formed to be large, the contact surface pressure becomes low, wear of the contact portion and the inner surface of the heating cylinder Shaving is prevented.

The contact area between the first backflow prevention ring and the second backflow prevention ring is designed to be smaller than the contact area. However, as described above, the first backflow prevention ring operates at a low speed. Since they rotate, the relative rotation of the first and second backflow prevention rings does not occur or does not increase so much, and the contact surface between them has little risk of wear.

On the other hand, during the injection operation of the injection screw, the contact area of the contact portion between the first backflow prevention ring and the second backflow prevention ring is smaller than the contact area of the contact portion between the screw head and the first backflow prevention ring. The second backflow prevention ring immediately separates from the first backflow prevention ring and comes into contact with the front end surface of the injection screw to reliably prevent backflow of the resin. That is, the structure has extremely high seal response.

Further, according to the backflow prevention device of the injection molding machine of the second aspect, during the measurement operation of the injection screw,
When the second backflow prevention ring comes into contact with the first backflow prevention ring, the first backflow prevention ring and the second backflow prevention ring slide because they engage with each other so that they rotate integrally. No wear and no risk of wear.

Even during the injection operation, the contact area of the engagement portion between the first backflow prevention ring and the second backflow prevention ring is smaller than the contact area of the contact portion between the screw head and the first backflow prevention ring. Since the second backflow prevention ring is immediately separated, the seal responsiveness is improved and the backflow of resin is prevented.

[0016]

1 to 4 show a first embodiment of the present invention. Since the basic structure and operation are the same as those of the conventional backflow prevention device of FIG. 7, the corresponding parts are designated by the same reference numerals and detailed description thereof will be omitted.

As shown in FIGS. 1 and 2, the backflow prevention ring 10 movably fitted on the small-diameter shaft 4 of the present embodiment has a first backflow prevention ring 11 (provided on the screw head 3 side. Hereinafter, the first ring 11 will be abbreviated.) And a second backflow prevention ring 12 (hereinafter, abbreviated as the second ring 12) provided on the injection screw 2 side. In addition, reference numerals 2b and 3c in the drawing denote wear-resistant spacers embedded in the front end surface 2a of the injection screw 2 and the rear end surface 3b of the screw head 3, and these spacers 2b and 3c.
The wear due to sliding with the backflow prevention ring 10 is reduced by c.

The first ring 11 has an outer diameter slightly smaller than the inner diameter of the heating cylinder 1, and has a shaft hole 11 larger in diameter than the small diameter shaft 4.
It is a cylindrical member in which a is formed. This first ring 1
The front end surface 11b and the rear end surface 11c of No. 1 are smooth surfaces, and the front end surface 11b slidably contacts the rear end surface 3b formed perpendicularly to the axis of the screw head 3.
The contact portion B between the front end surface 11b of the first ring 11 and the rear end surface 3b of the screw head 3 is, as shown in FIG.
It is designed to have a sufficiently large contact area.

The second screw provided on the injection screw 2 side
The ring 12 is a cylindrical member having the same outer peripheral diameter as the first ring 11, and has a shaft hole 12a having a diameter larger than that of the small diameter shaft 4 on the injection screw 2 side, and also communicates with this shaft hole 12a. A hole 12b having a larger diameter than the shaft hole 12a is provided on the head 3 side.
Are formed coaxially. The front end surface 12c of the second ring 12 is formed as an annular surface having a small area and slidably contacts the rear end surface 11c of the first ring 11. Thereby, the contact portion C between the first ring 11 and the second ring 12
As shown in FIG. 1, it is a portion of the outer periphery of the first ring 11 that contacts in an annular shape with a small area, and the contact area is sufficiently smaller than the contact portion B. The rear end surface 12d of the second ring 12 abuts on the front end surface 2a of the injection screw 2 so that the backward flow of the resin is prevented.

In the backflow prevention device of the present embodiment having the above-described structure, when the injection screw 2 is operated for metering, the first and second rings 11, 12 are moved forward along the small diameter shaft 4 as shown in FIG. Move and leave the injection screw 2. The front end surface 11 of the first ring 11 is attached to the rear end surface 3b of the screw head 3.
b is in contact, and the front end face 12c of the second ring 12 is in contact with the rear end face 11c of the first ring 11. The resin plasticized while the first ring 11 and the second ring 12 also rotate as the screw head 3 rotates rotates.
2. It passes through the shaft holes 12a, 12b, 11a of the first ring 11, passes through the flow groove 3a, and flows in front of the screw head 3 to be weighed.

In the above, during the measuring operation of the injection screw 2, the first ring 1 is rotated along with the rotation of the screw head 3.
1 also rotates, but the first ring 11 in the high-viscosity resin
Rotates at a lower speed than the screw head 3 due to the viscous resistance of the resin. Then, the first ring 11 and the screw head 3
Although the contact portion B with and slides, the contact area of the contact portion B is designed to be sufficiently large, so that the contact surface pressure becomes low and abrasion of the contact portion B and galling of the inner surface of the heating cylinder 1 are prevented. Further, as described above, since the first ring 11 rotates at a low speed, the first ring 12 rotates with the first ring 11, and even if there is relative rotation with the first ring 11, it does not become large. , The contact portion C between the first ring 11 and the second ring 12 is designed to have a small contact area, the contact portion C
There is almost no risk of wear.

During the injection operation of the injection screw 2,
As shown in FIG. 3, the second ring 12 moves rearward along the small diameter shaft 4, and then the end face 12d abuts on the front end face 2a of the injection screw 2 to prevent resin backflow. In addition,
After the second ring 12 has moved, as shown in FIG.
The first ring 11 moves rearward and contacts the front end surface 12c of the second ring 12.

During the injection operation of the injection screw 2,
Since the contact area of the contact portion C between the first ring 11 and the second ring 12 is smaller than the contact area of the contact portion B between the screw head 3 and the first ring 11, the screw head 3 and the first ring 11 at the contact portion B are contacted. The adhesion force between the first ring 11 and the second ring 12 at the contact portion C becomes smaller than the adhesion force between the first ring 11 and the second ring 12, and the second ring 12 is separated from the first ring 11 before the first ring 11 is separated from the screw head 3. It immediately separates and abuts the front end surface 2a of the injection screw 2 to reliably prevent resin backflow. That is, the structure has extremely high seal response. The first ring 11, which is in contact with the screw head 3, also moves toward the second ring 12 side after the second ring 12.

Therefore, the backflow prevention ring 10 of this embodiment
The first ring 11 and the first ring 1 formed so that the contact area B with the screw head 3 has a large contact area.
Since the contact portion C with the first ring 1 is composed of the second ring 12 formed so as to have a small contact area, it is possible to prevent wear and galling during the metering operation of the injection screw 1, and to prevent the injection screw 1 from being damaged. It is possible to provide a backflow prevention device that enhances the seal responsiveness during the injection operation of 2 and reliably prevents the backflow of resin.

Next, FIGS. 5 and 6 show a second embodiment of the present invention. In this embodiment, the same components as those shown in FIGS. 1 to 4 are designated by the same reference numerals and the description thereof will be omitted.

The backflow preventing ring 15 of this embodiment is different from that of the first embodiment in that the rear end surface 11c of the first ring 11 and the front end surface 12c of the second ring 12 have a small diameter shaft 4 on each other. That is, the engaging portion 16 having an uneven shape is formed so as to be relatively movable only in the axial direction. That is, on the outer peripheral surface on the rear end surface 11c side of the first ring 11, a plurality of recesses 16a are formed at predetermined intervals in the circumferential direction. A plurality of protrusions 16b that enter the respective recesses 16a are formed on the outer peripheral portion of the second ring 12 on the front end face 12c side. The contact area between the concave portion 16a and the convex portion 16b is designed to be smaller than the contact area of the contact portion B. As shown in FIG. 5, the axial length L1 of the concave portion 16a and the convex portion 16b is set larger than the moving range L2 of the backflow prevention ring 15.

The backflow prevention ring 15 having the above structure is
During the measuring operation of the injection screw 2, the first ring 11
When the second ring 12 comes into contact with the concave portion 16a, the convex portion 16
Since b enters and engages with each other, the first ring 11 and the second ring 12 rotate integrally without rotating relative to each other, and therefore there is no possibility of wear at the contact portion between them. As a result, a more reliable backflow prevention device can be obtained. Further, even during the injection operation, the contact area between the concave portion 16a and the convex portion 16b is smaller than the contact area of the contact portion B, so that the convex portion 16b is immediately separated from the concave portion 16a. Can provide a high anti-reflux ring.

The first ring 11 is used in this embodiment.
Although the concave portion 16a and the convex portion 16b are formed on the second ring 12, the same operational effect can be obtained by forming the convex portion 16a on the first ring 11 and the concave portion 16b on the second ring 12. it can.

[0029]

According to the backflow prevention device of the injection molding machine of the first aspect of the present invention, even if the screw head rotates during the metering operation of the injection screw, the first backflow slides on the rear end surface of the screw head. Since one side surface of the prevention ring is formed so as to have a large contact area, the contact surface pressure is reduced and wear and galling can be prevented. On the other hand, at the time of injection operation of the injection screw, one side surface of the second backflow prevention ring that slides with the other side surface of the first backflow prevention ring is formed with a small contact area. By separating from the first backflow prevention ring and contacting the injection screw, the seal responsiveness can be improved and the backflow of resin can be reliably prevented.

According to the backflow prevention device for the injection molding machine of the second aspect, even if the screw head rotates during the metering operation of the injection screw, the first backflow prevention ring that slides with the rear end surface of the screw head is used. Since one side surface is formed with a large contact area, the contact surface pressure can be reduced to prevent wear and galling, and the other side surface of the first backflow prevention ring and one side surface of the second backflow prevention ring. Since an engaging portion that integrally rotates both rings is formed in
The first backflow prevention ring and the second backflow prevention ring do not slide due to relative rotation, and wear of their contact portions can be completely prevented. Further, during the injection operation of the injection screw, since the engaging portion between the first backflow prevention ring and the second backflow prevention ring is formed with a small contact area, the second backflow prevention ring is separated from the first backflow prevention ring. Since it immediately separates and abuts against the injection screw, it is possible to improve the seal responsiveness and prevent resin backflow.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of essential parts showing a backflow prevention device of a first embodiment according to the present invention during a metering operation.

FIG. 2 is a diagram showing a tip portion of the screw head in FIG.

FIG. 3 is a sectional view of relevant parts showing the movement of the second backflow prevention ring during the injection operation of the first embodiment.

FIG. 4 is a sectional view of an essential part showing the movement of the first backflow prevention ring during the injection operation of the first embodiment.

FIG. 5 is an external view of the inside of the heating cylinder showing the backflow prevention device of the second embodiment according to the present invention.

FIG. 6 is a cross-sectional view of essential parts at the time of injection operation of the second embodiment.

FIG. 7 is a cross-sectional view of a conventional backflow prevention device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Heating cylinder 2 Injection screw 2a Front end surface of injection screw 3 Screw head 3a Flow groove 3b Rear end surface of screw head 10 Backflow prevention ring (first embodiment) 11 First backflow prevention ring 11b Front end surface 11c Rear end surface 12 Second Backflow prevention ring 12c Front end surface 12d Rear end surface 15 Backflow prevention ring (second embodiment) 16 Locking portion 16a Recess 16b Convex portion B Contact portion between first backflow prevention ring and screw head C First backflow prevention ring and first 2 Contact area with backflow prevention ring

Claims (2)

(57) [Claims] 1. An injection screw having a screw head attached to a front end 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 in the heating cylinder. The small diameter shaft contacts the injection screw during injection operation of the injection screw to prevent backward flow of the molten resin, and when the injection screw is measured, moves relatively to the screw head side and moves to the front of the screw head. In a backflow prevention device of an injection molding machine, in which a cylindrical backflow prevention ring that allows the resin to flow freely is inserted movably back and forth, in the backflow prevention ring, a front end surface of the backflow prevention ring slides on a rear end surface of the screw head. A second backflow prevention ring that has a first backflow prevention ring that movably contacts and a front end surface that slidably contacts the rear end surface of the first backflow prevention ring, and whose rear end surface abuts the front end surface of the injection screw. The contact portion between the screw head and the first backflow prevention ring is formed with a large contact area, and the contact portion between the first backflow prevention ring and the second backflow prevention ring is A backflow prevention device for an injection molding machine, wherein the contact area is smaller than the contact area. 2. The backflow prevention device for an injection molding machine according to claim 1, wherein the first backflow prevention ring is replaced with a second backflow prevention ring in which a rear end surface and a front end surface of the first backflow prevention ring slidably contact each other. A second backflow prevention ring is provided which rotates integrally with the first backflow prevention ring by engagement with the rear end surface of the prevention ring and allows relative movement with the first backflow prevention ring in the axial direction. The contact area of the engaging portion between the first backflow prevention ring and the second backflow prevention ring is smaller than the contact area between the screw head and the first backflow prevention ring. Backflow prevention device.