JP2000309043A - Back flow preventing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the durability of a back flow preventing device and the quality of a molded article. SOLUTION: A screw 12 and a check ring 34 arranged on the outer periphery of a screw head 30 and having an engaging projection formed at the front end thereof are provided. The notch engaged with the engaging projection to permit the revolution of the check ring 34 by a predetermined angle is formed to the screw hand 30. A first resin flow channel is formed to a seal ring 33 and a second resin flow channel is formed to the check ring 34 and the first and second resin flow channels are allowed to selectively communicate with each other accompanied by the rotation of the screw 12 in first and second directions. Since the engaging projection is integrally formed along with the check ring 34, the durability of a back flow preventing device can be enhanced.

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 rotatable in a heating cylinder of the injection device.
The screw is provided so as to be able to move forward and backward, and the screw can be rotated or moved forward and backward by the driving means. Then, during the measuring step, the screw is retracted while rotating in the forward direction, the resin dropped from the hopper is melted and stored in front of the screw head, and during the injection step, the screw is advanced to inject the resin from the injection nozzle. I have to.

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

[0004] In the figure, 11 is a heating cylinder,
The heating cylinder 11 has an injection nozzle 13 at a front end (left end in the figure). A screw 12 is provided in the heating cylinder 11 so as to be rotatable and movable back and forth, so that the screw 12 can be rotated and advanced and retracted by driving means (not shown).

The screw 12 extends rearward (to the right in the drawing) inside 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 screw (helical) flight 15 is formed on the surface of the main body of the screw 12, that is, the surface of the screw main body 18, and a groove 16 is formed by the flight 15.

In the injection device having the above-described structure, when the driving means is driven to retreat (move 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. , Is advanced into the groove 16 by moving into the heating cylinder 11 (moving to the left in the drawing), is melted by a heater (not shown), and is in front of the screw head 14 (to the left in the drawing).
Is stored in

When the driving means is driven to advance the screw 12 during the injection step, the resin stored in front of the screw head 14 is injected from the injection nozzle 13 and the cavity space of the mold (not shown). Is filled.

By the way, a backflow prevention device is provided to prevent the resin stored in front of the screw head 14 from flowing backward during the injection step.

For this purpose, the screw head 14
Has a conical (conical) head body 21 at the front end, a cylindrical portion 19 at the center, and a small diameter portion 17 at the rear end. And
An annular check ring 20 is rotatably disposed on the outer periphery of the cylindrical portion 19, and a presser 22 is fixed on the outer periphery of the small diameter portion 17.

On the outer circumference of the check ring 20, axially extending grooves 20a are formed at a plurality of positions in the circumferential direction, and cutouts 20b are formed at two positions at the front end over a predetermined angle. Further, the pin 2 is passed through the
3 are attached, and both ends of the pin 23 are notched 20b.
Placed inside. In this case, the check ring 20 is rotated by a predetermined angle θ, and further rotation is restricted. To this end, the notch 20b has a sector shape,
A first regulating surface is formed at one end in the circumferential direction, and a second regulating surface is formed at the other end in the circumferential direction. In addition, the presser 22
The outer periphery of the groove 20 is provided at a plurality of positions in the circumferential direction.
A groove 22a extending in the axial direction is formed corresponding to a.
Each of the grooves 20a and 22a has an outer periphery open, and the groove 20a forms a resin flow path in the non-return ring, and the groove 22a forms a resin flow path in the pressing die. And
When the check ring 20 is rotated with respect to the screw head 14, the resin flow path in the check ring and the resin flow path in the pressing member are selectively communicated.

In this case, at the time of the measuring step, the screw 12
When the screw head 14 is retracted while rotating in the forward direction, the screw head 14 is also rotated. At this time, check ring 20
Is rotatably disposed with respect to the screw head 14, so that the screw 12 is stopped until the screw 12 rotates by the angle θ, and the pin 2 is attached to the first regulating surface of the notch 20b.
After hitting 3, it is rotated with the screw 12 thereafter. When the pin 23 hits the first regulating surface,
The check ring 20 is placed at the communication position, and the resin flow path in the check ring and the resin flow path in the pusher are communicated. As a result, the resin in the groove 16 flows forward through the resin flow path in the pusher and the resin flow path in the check ring.

In this way, when the measuring step is completed,
The screw 12 is rotated in the opposite direction by the angle θ. Then, when the check ring 20 is rotated with respect to the screw head 14 and the pin 23 hits the second regulating surface of the notch 20b, the check ring 20 is placed in the cut-off position, and the check ring 20 The resin flow path and the resin flow path in the pusher are shut off.

Subsequently, when the screw 12 is advanced in the injection step, the resin stored in front of the screw head 14 flows backward and tries to move backward. Since the internal resin flow path is blocked, it is possible to prevent the resin in front of the screw head 14 from flowing backward.

Therefore, it is possible to suppress the occurrence of variation in the amount of resin filling the cavity space in the injection step.

[0015]

However, in the above-mentioned conventional backflow prevention device, the screw 12 is rotated in the forward direction and the reverse direction for each molding cycle, so that the first and second regulating surfaces are rotated. Since the pin 23 is hit, rotational torques in opposite directions are repeatedly applied to the pin 23. The rotation torque is controlled by the screw 12 which is a molding condition.
It varies depending on the rotation speed of the resin, the characteristics of the resin, and the like.
In the injection step, a portion of the pin 23 protruding from the screw head 14 receives a resin pressure accompanying the injection, so that a shearing stress is generated in the pin 23 every molding cycle.

As described above, since a strong stress field is repeatedly generated in the pin 23 for each molding cycle, the durability of the backflow prevention device is reduced. If the pin 23 is broken, it is impossible to prevent the resin from flowing backward in the injection step, so that the amount of the resin filled in the cavity space is reduced by that amount, and the quality of the molded product is reduced. . Further, if broken pieces of the pin 23 are clogged in the injection nozzle 13 or mixed with the resin, the quality of the molded product is significantly reduced.

Therefore, it is conceivable to increase the diameter of the pin 23 to increase the strength. However, due to the design of the injection device, the screw head 14 and the heating cylinder 11
It is necessary to make the ratio of the cross-sectional area through which the resin passes between at least 10% or more, so that the diameter of the screw head 14 is set to at least １ ／ of the diameter of the screw body 18 (the outer diameter of the flight 15). I can't. Therefore, when the diameter of the pin 23 is increased, the screw head 1
4 becomes small, and the durability of the screw head 14 is reduced.

The pin 23 is detachably mounted on the screw head 1 so that it can be removed for maintenance and management.
It is attached by fitting into (4),
If the pin 23 comes off the screw head 14 due to the application of rotational torque, resin pressure or the like to the pin 23, it becomes impossible to prevent the resin from flowing backward in the injection process, so that the resin filled in the cavity space is not filled. And the quality of the molded article is reduced. In addition, if the detached pin 23 becomes clogged in the injection nozzle 13 or damages other parts, the quality of the molded product is significantly reduced. As a result, when fitting the pin 23 into the screw head 14, it is necessary to increase the fitting accuracy, so that the cost of the backflow prevention device increases.

An object of the present invention is to provide a backflow prevention device which can solve the problems of the conventional backflow prevention device and can improve durability and quality of a molded product.

[0020]

For this purpose, in the backflow prevention device of the present invention, a screw provided with a screw main body, a seal ring and a screw head, and disposed on the outer periphery of the screw head and locked at a front end thereof A protrusion formed integrally with the check ring.

A notch is formed in the screw head so as to be locked with the locking projection and allows the rotation of the check ring by a predetermined angle.

Also, a first resin flow path is formed in the seal ring, a second resin flow path is formed in the check ring, and the screw is rotated in the first and second directions. Accordingly, the first and second resin flow paths are selectively communicated.

[0023]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a longitudinal sectional view showing a state of communication of a flow path of the backflow prevention device according to the embodiment of the present invention, FIG. 3 is a front view showing a state of communication of the flow path of the backflow prevention device according to the embodiment of the invention, FIG. 4 is a partial cross-sectional view of the screw head according to the embodiment of the present invention, FIG. 5 is a vertical cross-sectional view of the check ring according to the embodiment of the present invention, and FIG. FIG. 7 is a front view of the seal ring according to the embodiment of the present invention, FIG. 8 is a left side view of the seal ring according to the embodiment of the present invention, FIG. 9 is a cross-sectional view taken along line AA of FIG. 10 is a sectional view taken along line BB of FIG. 1, FIG. 11 is a sectional view taken along line CC of FIG. 1, FIG. 12 is a sectional view taken along line DD of FIG. 1, FIG. 13 is a sectional view taken along line EE of FIG. FIG. 15 is a longitudinal sectional view showing a state in which the backflow prevention device according to the embodiment of the present invention is shut off, and FIG. F-F arrow 示図, FIG. 16 is a cross-section G-G of FIG 14.

In the drawing, reference numeral 11 denotes a heating cylinder of the injection device, and the heating cylinder 11 has an injection nozzle (not shown) at a front end (left end in FIG. 1). A screw 12 is provided in the heating cylinder 11 so as to be rotatable and movable back and forth, so that the screw 12 can be rotated and advanced and retracted by driving means (not shown). A control device (not shown) is provided to control the driving of the driving means.

The screw 12 extends rearward (to the right in FIG. 1) inside the heating cylinder 11 and has a rear end (FIG. 1).
At the right end) and a screw head 30 at the front end. A spiral flight 15 is provided on the surface of the screw body 18.
Is formed, and a groove 16 is formed by the flight 15.

In the injection apparatus having the above-described configuration, when the driving means is driven to rotate the screw 12 in the positive direction as the first direction and move backward (moving to the right in FIG. 1) during the measuring step, The pellet-shaped resin in the hopper that is not inserted enters the heating cylinder 11 and moves forward (moves to the left in FIG. 1) in the groove 16, is melted by a heater (not shown), and is melted in front of the screw head 30 ( (Left side in FIG. 1).

When the driving means is driven to advance the screw 12 without rotating it during the injection step, the resin stored in front of the screw head 30 is injected from the injection nozzle, and a mold (not shown) is used. Is filled in the cavity space.

By the way, a backflow prevention device is provided to prevent the resin stored in front of the screw head 30 from flowing backward during the injection step.

For this purpose, the screw head 30
Is a conical head tip 30 from the front end to the rear end.
a, a large diameter portion 30b, a small diameter portion 31, and a fixing portion 35,
The small diameter portion 31 is smaller in diameter than the large diameter portion 30b.
The small-diameter portion 31 has a rear end (right end in FIG. 1)
Tapered portion 31a whose outer diameter increases from front to back
The fixing portion 35 has a screwing portion 3 for fixing the screw head 30 to the screw body portion 18 at the rear end.
5a. An annular seal ring 33 is attached to the front end of the screw body 18.

The seal ring 33 has a seal surface S at its front end.
1 and a plurality of first grooves 43 having a substantially semicircular cross-section at a plurality of positions (six positions in the circumferential direction in the present embodiment) on the outer periphery are extended at an equal pitch in the axial direction. It is formed. Each first groove 43 forms a first resin flow path. A key groove 33b for positioning the seal ring 33 with respect to the screw head 30 is formed on the inner peripheral surface of the seal ring 33.

An annular check ring 34 is rotatably disposed on the outer periphery of the small diameter portion 31. The check ring 3
No. 4 has a seal surface S2 at the rear end and an inner peripheral surface S3 at the inner periphery, and has a substantially semicircular cross section at a plurality of positions (six positions in the circumferential direction in the present embodiment) on the inner periphery. Have
The second grooves 45, which are shallower from the rear to the front, are formed at an equal pitch so as to extend in the axial direction. Each second groove 45
Constitutes a second resin flow path having a resin inlet 46 on the seal surface S2. An annular space 48 is formed from the center to the front end in the check ring 34, and the space 48 forms a third resin flow path.
A screw 1 is provided between the first and second grooves 43 and 45.
2 is selectively communicated with the rotation.

At the front end of the check ring 34, locking projections 41 are integrally formed at two locations in the circumferential direction so as to protrude forward. Also, the large diameter portion 30b
Notches 55 are formed at two rear end portions at a predetermined angle. The locking projection 41 is provided with the notch 5
5 to allow rotation of the check ring 34 by a predetermined angle θ and restrict further rotation. For this purpose, the notch 55 has a first regulating surface S4 at one end in the circumferential direction and a second regulating surface S5 at the other end.
Is formed. The notch 55 also functions as a resin flow path.

When the screw head 30 and the check ring 34 are relatively rotated with the rotation of the screw 12, the first and second resin flow paths are selectively communicated.

In this case, the screw 12
When rotating backward in the forward direction (the direction of the arrow in FIG. 10), the screw head 30 is also rotated. At this time, the check ring 34 is
0 so that the screw 12
Is stopped until it is rotated by the angle θ, and as shown in FIG. 10, when the locking projection 41 hits the first regulating surface S4 of the notch 55, it is rotated with the screw 12 thereafter. When the locking projection 41 hits the first regulating surface S4, the check ring 34 is placed at the communicating position,
The first and second resin flow paths are communicated. As a result, the resin in the groove 16 flows forward through the first to third resin flow paths and is stored in front of the screw head 30.

When the measuring step is completed in this way,
The screw 12 is rotated in the opposite direction (the direction of the arrow in FIG. 15) as the second direction by the angle θ. Along with this, the check ring 34 is rotated with respect to the screw head 30, and as shown in FIG. 15, the locking projection 41 hits the second regulating surface S 5 of the notch 55, and the check ring 34 Is placed at the blocking position, and the first and second resin flow paths are blocked.

Subsequently, when the injection process is started and the screw 12 is advanced, the resin stored in front of the screw head 30 flows backward and moves backward, but the first and second resins are moved. Since the flow path is blocked, the resin in front of the screw head 30 can be prevented from flowing backward.

Therefore, it is possible to suppress the occurrence of a variation in the amount of resin filled in the cavity space in the injection step.

As described above, the first groove 43 is formed on the outer periphery of the seal ring 33, and the second groove 45 is formed on the check ring 34.
When the check ring 34 is placed at the blocking position, the first and second grooves 43 and 45 do not communicate with each other. Therefore, backflow of the resin in front of the screw head 30 can be completely prevented.
Since the second and third resin flow paths are formed between the check ring 34 and the small-diameter portion 31 of the screw head 30, the resin stays between the check ring 34 and the screw head 30. There is no. Therefore, the deterioration of the resin can be prevented, and the operation of the check ring 34 can be stabilized.

Further, the screw 12 is used for each molding cycle.
As the is rotated in the forward and reverse directions, the locking projections 41 contact the first and second regulating surfaces S4 and S5. Join repeatedly. Then, in the injection step, the locking projection 41 receives a resin pressure accompanying the injection. Therefore, a strong stress field is repeatedly generated in the locking projection 41 every molding cycle.

However, since the locking projection 41 is formed integrally with the check ring 34, the durability of the backflow prevention device can be improved. Since the locking projection 41 is not broken, the resin can be reliably prevented from flowing backward in the injection step. Therefore, the amount of the resin filled in the cavity space can be stabilized, and the quality of the molded product can be improved.

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.

[0043]

As described above in detail, according to the present invention, in the backflow prevention device, a screw having a screw body, a seal ring and a screw head, and a screw provided on the outer periphery of the screw head, A check ring integrally formed with a locking projection at the front end.

A notch is formed in the screw head so as to be locked with the locking projection and allows the rotation of the check ring by a predetermined angle.

Further, a first resin flow path is formed in the seal ring, a second resin flow path is formed in the check ring, and the screw is rotated in the first and second directions. Accordingly, the first and second resin flow paths are selectively communicated.

In this case, as the screw is rotated in the first and second directions for each molding cycle, the first and second regulating surfaces of the notch are brought into contact with the locking projections. , Rotational torques in opposite directions are repeatedly applied. Then, in the injection step, the locking projection receives a resin pressure accompanying the injection. Therefore, a strong stress field is repeatedly generated in the locking projection every molding cycle.

However, since the locking projection is formed integrally with the check ring, the durability of the backflow prevention device can be improved. Since the locking projection is not broken, it is possible to reliably prevent the resin from flowing backward in the injection step. Therefore, the amount of the resin filled in the cavity space can be stabilized, and the quality of the molded product can be improved.

[Brief description of the drawings]

FIG. 1 is a vertical cross-sectional view showing a communication state of a flow path of a backflow prevention device according to an embodiment of the present invention.

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

FIG. 3 is a front view showing a flow path communicating state of the backflow prevention device according to the embodiment of the present invention.

FIG. 4 is a partial cross-sectional view of the screw head according to the embodiment of the present invention.

FIG. 5 is a longitudinal sectional view of the check ring according to the embodiment of the present invention.

FIG. 6 is a right side view of the check ring according to the embodiment of the present invention.

FIG. 7 is a front view of the seal ring according to the embodiment of the present invention.

FIG. 8 is a left side view of the seal ring according to the embodiment of the present invention.

FIG. 9 is a sectional view taken along line AA of FIG. 8;

FIG. 10 is a view taken along the line BB of FIG. 1;

FIG. 11 is a sectional view taken along the line CC of FIG. 1;

FIG. 12 is a sectional view taken along line DD of FIG. 1;

FIG. 13 is a sectional view taken along line EE of FIG. 1;

FIG. 14 is a vertical cross-sectional view illustrating a flow path blocking state of the backflow prevention device according to the embodiment of the present invention.

FIG. 15 is a diagram showing an arrow FF in FIG. 14;

FIG. 16 is a sectional view taken along line GG of FIG. 14;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 12 Screw 18 Screw main body 30 Screw head 33 Seal ring 34 Check ring 41 Locking projection 43, 45 First and second grooves 55 Notch θ angle

Claims (1)

[Claims] 1. A check ring comprising: (a) a screw having a screw body, a seal ring and a screw head; and (b) a check ring disposed on the outer periphery of the screw head and integrally formed with a locking projection at a front end. And having
(C) a notch is formed in the screw head so as to be locked with the locking projection to allow rotation of the check ring by a predetermined angle; and (d) a first resin flow path is formed in the seal ring. Is formed, (e) a second resin flow path is formed in the check ring, and (f) the first and second screws are rotated in the first and second directions. Wherein the resin flow paths are selectively communicated with each other.