JP3345315B2 - 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, an injection molding machine has an injection device, and a screw is disposed in a heating cylinder of the injection device so as to be rotatable and movable back and forth, and the screw is rotated or moved forward and backward by driving means. Or so.
Then, during the metering step, the screw is retracted while rotating forward, the resin dropped from the hopper is melted and stored in front of the screw head, and at the time of the injection step, the screw is advanced to inject the resin from the injection nozzle. Like that.

FIG. 2 is a sectional view of a main part of a conventional injection device. In the figure, reference numeral 11 denotes a heating cylinder, and the heating cylinder 11 has an injection nozzle (not shown) at a front end (left end in the figure). A screw 12 is disposed in the heating cylinder 11 so as to be rotatable and movable back and forth, and the screw 12 is rotated and moved forward and backward by a driving unit (not shown).

The screw 12 extends rearward (to the right in the drawing) in the heating cylinder 11, is connected to the driving means at a rear end (the right end in the drawing), and has a screw head 14 at the front end. A spiral flight 15 is formed on the surface of the metering portion 18 of the screw 12.
A groove 16 is formed along.

In the injection device having the above-described structure, when the driving means is driven to rotate backward (moving to the right in the drawing) while the screw 12 is rotated forward in the measuring step, the pellet-shaped resin in the hopper (not shown) is removed. Heating cylinder 11
And moves forward in the groove 16 (moves to the left in the figure)
Is melted by a heater (not shown)
It is stored in front of the screw head 14 (to the left in the figure).

When the screw 12 is moved forward by driving the driving means during the injection step, the resin stored in front of the screw head 14 is injected from the injection nozzle and the cavity space of a mold (not shown) is formed. Is filled. By the way, at the time of the injection step, a backflow prevention device is provided so that the resin stored in front of the screw head 14 moves backward, that is, does not flow backward, as the screw 12 advances.

For this purpose, the screw head 14
Has a conical (conical) head body 21 at the front (left part in the figure) and a small diameter part 19 at the rear part (right part in the figure). An annular check ring 20 is disposed around the small diameter portion 19, and a resin flow path 24 is formed between the small diameter portion 19 and the check ring 20. A seal ring 22 is provided at the front end of the metering portion 18 so as to be able to contact and separate from the rear end of the check ring 20.

In this case, when the screw 12 is advanced during the injection step, the resin stored in front of the screw head 14 tends to flow backward.
0 moves relatively rearward with respect to the screw 12 by the pressure of the resin, and the rear end of the check ring 20 abuts on the seal ring 22 to perform sealing. Therefore, the resin stored in front of the screw head 14 can be prevented from flowing backward.

On the other hand, when the screw 12 is retracted while rotating in the forward direction during the measuring process, the check ring 20 moves relatively forward with respect to the screw 12 due to the pressure of the resin. The front end abuts on the rear end of the head main body 21, but notches 25 extending in the axial direction are formed at a plurality of locations around the head main body 21, so that the movement of the resin is not hindered.

At the front end of the check ring 20, a projection 26 is formed at a predetermined position in the circumferential direction.
6 is engaged with the notch 25. Therefore, when the screw 12 is rotated, the check ring 20 is also rotated.

[0011]

However, in the above-mentioned conventional backflow prevention device, when a resin mixed with a reinforcing material such as glass fiber is used, galling occurs in each sliding (sliding) moving portion of the injection device. The durability of the injection device is reduced, or the abrasion powder generated by galling is mixed into the resin to lower the quality of the molded product.

FIG. 3 is a diagram showing a first state of the check ring in the conventional backflow prevention device, and FIG. 4 is a diagram showing a second state of the check ring in the conventional backflow prevention device. In the figure, 11 is a heating cylinder, 20 is a check ring, 26
Is a protrusion. As shown in the figure, in the case of the counter-rotating backflow prevention device, when the screw 12 (FIG. 2) is rotated, the check ring 20 is also rotated, and the heating cylinder 11 is rotated.
And the outer peripheral surface of the check ring 20 slides,
Galling occurs on the inner peripheral surface of the heating cylinder 11 and the outer peripheral surface of the check ring 20.

In particular, normally, the check ring 20 is arranged as shown in FIG. 3, while foreign matter, unmelted resin, etc. are interposed between the check ring 20 and the seal ring 22. When the screw 12 is bent or the rear end face of the check ring 20 or the front end face of the seal ring 22 is deformed, the check ring 20 is inclined as shown in FIG. As a result, the outer peripheral surface of the projection 26 and the outer peripheral surface near the rear end of the check ring 20 are
As a result, the surface pressure in contact with the inner peripheral surface increases, and the outer peripheral surface of the projection 26, the outer peripheral surface near the rear end of the check ring 20, and the inner peripheral surface of the heating cylinder 11 are locally galled.

Therefore, it is conceivable to increase the clearance between the outer peripheral surface of the check ring 20 and the inner peripheral surface of the heating cylinder 11 or shorten the check ring 20, but it is necessary to increase the clearance. When the check ring 20 is shortened, the sealing performance of the check ring 20 is reduced, so that it is not possible to sufficiently prevent the resin from flowing backward, and when a low-viscosity resin is used, the cushion amount varies. Or do it. It is also conceivable to form a not-shown groove, dimple-shaped depression (hollow) on the outer periphery of the check ring 20, but it is possible to prevent the occurrence of local galling when the check ring 20 is inclined. Can not do it.

The present invention solves the problems of the above-mentioned conventional backflow prevention device, prevents galling at each sliding portion of the injection device, and reduces the durability of the injection device and the quality of molded products. It is an object of the present invention to provide a backflow prevention device capable of sufficiently preventing backflow of resin without causing the backflow.

[0016]

For this purpose, in the backflow prevention device of the present invention, a metering portion, a seal ring disposed at a front end of the metering portion, and a head attached to the metering portion, A screw head having a main body and a small-diameter portion, and a check ring provided around the small-diameter portion and having, at a front end, a projection engaged with a notch formed in the head main body. Have.

The outer diameter of the check ring is reduced from the rear end to the front end.

[0018]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 5 is a sectional view of a main part of the injection device according to the embodiment of the present invention. In the figure, reference numeral 11 denotes a heating cylinder;
1 has an injection nozzle (not shown) at the front end (left end in the figure). In the heating cylinder 11, a screw 1
The screw 12 is rotatably and reciprocally movable, and the screw 12 is rotated or moved forward and backward by a driving means (not shown).

The screw 12 extends rearward (to the right in the figure) inside the heating cylinder 11, is connected to the driving means at a rear end (the right end in the figure), and has a screw head 14 at the front end. A spiral flight 15 is formed on the surface of the metering portion 18 of the screw 12, and a groove 16 is formed along the flight 15.

In the injection device having the above-described configuration, when the driving means is driven to rotate backward (moving to the right in the drawing) while the screw 12 is rotated forward in the measuring step, the pellet-shaped resin in the hopper (not shown) is discharged. Heating cylinder 11
And moves forward in the groove 16 (moves to the left in the figure)
Is melted by a heater (not shown)
It is stored in front of the screw head 14 (to the left in the figure).

When the screw 12 is moved forward by driving the driving means during the injection step, the resin stored in front of the screw head 14 is injected from the injection nozzle, and the cavity space of a mold (not shown) is formed. Is filled. By the way, a backflow prevention device is provided so that the resin stored in front of the screw head 14 does not flow backward as the screw 12 advances during the injection step.

For this purpose, the screw head 14
Is a conical head body 2 at the front (left part in the figure).
1 has a small-diameter portion 19 at a rear portion (right portion in the figure).
An annular check ring 30 is disposed on the outer periphery of the small diameter portion 19, and a resin flow path 24 is formed between the small diameter portion 19 and the check ring 30. The metering unit 1
A seal ring 22 is provided at the front end of the seal ring 8 so as to be able to freely contact and separate from the rear end of the check ring 30.

In this case, when the screw 12 is advanced during the injection step, the resin stored in front of the screw head 14 tends to flow backward.
0 moves rearward relative to the screw 12 by the pressure of the resin, and the rear end of the check ring 30 contacts the seal ring 22 to perform sealing. Therefore, the resin stored in front of the screw head 14 can be prevented from flowing backward.

On the other hand, when the screw 12 is retracted while rotating in the forward direction during the measuring step, the check ring 30 moves forward relative to the screw 12 due to the pressure of the resin, and the check ring 30 The front end abuts on the rear end of the head main body 21, but notches 25 extending in the axial direction are formed at a plurality of locations around the head main body 21, so that the movement of the resin is not hindered.

At the front end of the check ring 30, a projection 36 is formed at a predetermined position in the circumferential direction.
6 is engaged with the notch 25. Therefore, when the screw 12 is rotated, the check ring 30 is also rotated. By the way, when a resin mixed with a reinforcing material such as glass fiber is used, if galling occurs in each sliding portion of the injection device, the durability of the injection device is reduced, or the abrasion powder generated by the galling is applied to the resin. It may be mixed to lower the quality of the molded product.

Therefore, the outer diameter of the check ring 30 is reduced from the rear end to the front end. FIG. 1 is a diagram illustrating a first state of the check ring according to the embodiment of the present invention, and FIG. 6 is a diagram illustrating a second state of the check ring according to the embodiment of the present invention. In the figure, 11 is a heating cylinder, 30 is a check ring, and 36 is a projection.

As shown in the figure, in the case of the counter-rotating type backflow prevention device, when the screw 12 (FIG. 5) is rotated, the check ring 30 is also rotated. Is reduced from the rear end (right end in the drawing) to the front end (left end in the drawing), so that the inner peripheral surface of the heating cylinder 11 and the outer peripheral surface of the check ring 30 do not slide. Therefore, it is possible to prevent the inner peripheral surface of the heating cylinder 11 and the outer peripheral surface of the check ring 30 from galling.

In particular, while the check ring 30 is usually arranged as shown in FIG. 1, foreign matter, unmelted resin or the like is interposed between the check ring 30 and the seal ring 22. When the screw 12 is bent or the rear end face of the check ring 30 or the front end face of the seal ring 22 is deformed, the check ring 30 is inclined as shown in FIG. However, since the outer diameter of the check ring 30 is reduced from the rear end to the front end, the outer peripheral surface of the projection 36 and the outer peripheral surface near the rear end of the check ring 30 are formed on the inner peripheral surface of the heating cylinder 11. The contact pressure does not increase. Therefore, it is possible to prevent local galling on the outer peripheral surface of the projection 36, the outer peripheral surface near the rear end of the check ring 30, and the inner peripheral surface of the heating cylinder 11. As a result, the abrasion powder does not mix into the resin, so that the quality of the molded product can be improved.

Further, it is not necessary to increase the clearance between the outer peripheral surface of the check ring 30 and the inner peripheral surface of the heating cylinder 11 or to shorten the check ring 30.
It is possible to sufficiently prevent the sealability from being reduced by the check ring 30 and to prevent the resin from flowing backward. When a low-viscosity resin is used, the cushion amount does not change. In addition, since a resin film is formed between the outer peripheral surface of the check ring 30 and the inner peripheral surface of the heating cylinder 11, the outer peripheral surface of the check ring 30 and the inner peripheral surface of the heating cylinder 11 are protected by the resin film. You. Therefore, the durability of the injection device does not decrease.

It should be noted that the present invention is not limited to the above-described embodiment, but can be variously modified based on the gist of the present invention, and they are not excluded from the scope of the present invention.

[0031]

As described above in detail, according to the present invention, in the backflow prevention device, the metering portion, the seal ring provided at the front end of the metering portion, and the metering portion are provided. A screw head having a head body portion and a small-diameter portion attached thereto, and a reverse head having a projection disposed around the small-diameter portion and having a front end engaged with a notch formed in the head main body portion. A stop ring.

The outer diameter of the check ring is reduced from the rear end to the front end. In this case, since the outer diameter of the check ring is reduced from the rear end to the front end, the inner peripheral surface of the heating cylinder and the outer peripheral surface of the check ring do not slide. Therefore, it is possible to prevent galling on the inner peripheral surface of the heating cylinder and the outer peripheral surface of the check ring.

In particular, foreign matter, unmelted resin or the like is caught between the check ring and the seal ring, the screw bends, the rear end face of the check ring, the front end of the seal ring, and the like. When the end face or the like is deformed, the check ring is inclined, but since the outer diameter of the check ring is reduced from the rear end to the front end, the outer peripheral surface of the protrusion and the vicinity of the rear end of the check ring are reduced. There is no increase in surface pressure at which the outer peripheral surface of the heater contacts the inner peripheral surface of the heating cylinder. Therefore, it is possible to prevent local galling on the outer peripheral surface of the protrusion, the outer peripheral surface near the rear end of the check ring, and the inner peripheral surface of the heating cylinder. As a result, the abrasion powder does not mix into the resin, so that the quality of the molded product can be improved.

Since there is no need to increase the clearance between the outer peripheral surface of the check ring and the inner peripheral surface of the heating cylinder and to shorten the check ring, the sealing performance of the check ring is reduced. The backflow of the resin can be sufficiently prevented, and the cushion amount does not change when a low-viscosity resin is used. Moreover, since the resin film is formed between the outer peripheral surface of the check ring and the inner peripheral surface of the heating cylinder, the outer peripheral surface of the check ring and the inner peripheral surface of the heating cylinder are protected by the resin film. Therefore, the durability of the injection device does not decrease.

[Brief description of the drawings]

FIG. 1 shows a first example of a check ring according to an embodiment of the present invention.
It is a figure showing the state of.

FIG. 2 is a sectional view of a main part of a conventional injection device.

FIG. 3 shows a first example of a check ring in a conventional backflow prevention device.
It is a figure showing the state of.

FIG. 4 shows a second example of the check ring in the conventional backflow prevention device.
It is a figure showing the state of.

FIG. 5 is a sectional view of a main part of the injection device according to the embodiment of the present invention.

FIG. 6 shows a second example of the check ring according to the embodiment of the present invention.
It is a figure showing the state of.

[Explanation of symbols]

 14 Screw head 18 Metering part 19 Small diameter part 21 Head main body part 22 Seal ring 25 Notch 30 Check ring 36 Projection

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B29C 45/00-45/84

Claims (1)

(57) [Claims] 1. A metering portion, (b) a seal ring disposed at a front end of the metering portion, and (c) a metering portion.
A screw head attached to the metering portion and having a head body portion and a small diameter portion; and (d) a screw head disposed around the small diameter portion and having a front end formed with a notch formed in the head body portion. A non-return ring having a projection to be fitted, and (e) the non-return ring has an outer diameter that decreases from a rear end to a front end.