JP3524262B2 - 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 a backflow prevention device for an injection molding machine, and more particularly to a backflow prevention device suitable for a material having a low melt viscosity.

[0002]

2. Description of the Related Art A conventional backflow prevention device for an injection molding machine is known, for example, as disclosed in Japanese Patent Laid-Open No. 6-297519. This is on the front side of the screw body,
An annular valve seat, a shaft portion, and a head portion of a screw head are sequentially provided, and a backflow prevention ring having an inner diameter larger than the outer diameter of the shaft portion is externally fitted to the shaft portion, the backflow prevention ring and the shaft portion. A backflow prevention ring device for forming a molten material passage between the backflow prevention ring and the backflow prevention ring is provided with an elastic body for biasing the backward valve portion so as to abut against the valve seat.

According to such a backflow prevention device of the injection molding machine, the weighing is accurately performed. That is, in particular, when a molten material having a low melt viscosity, for example, a metal such as magnesium, aluminum, zinc and lead or an alloy thereof is injection-molded, it is urged by an elastic body when shifting to the injection step after weighing. The backflow prevention ring rapidly retracts, and the backward valve portion comes into contact with the valve seat, so that the molten material is well suppressed from flowing backward in the molten material passage. In this way, the molten material is prevented from flowing backward in the molten material passage and returning to the screw body side, so that the preset molding conditions (measurement value, injection speed, ejection force, holding pressure, etc.) Since it is accurately transmitted, molding defects such as sink marks, voids, short shots, and weld lines are satisfactorily suppressed, and a molded product is prevented from becoming a defective product.

[0004]

However, in such a conventional backflow preventive device for an injection molding machine, the elastic body has a front end surface of the backflow prevention ring and a rearward facing annular side surface of the head portion of the screw head. Since the molten material flows through the molten material passage during the measuring step, the flow pressure of the molten material directly acts on the elastic body, and the elastic body is curved and deformed. Therefore, there is a technical problem that not only the elastic function of the elastic body gradually declines and the original function gradually decreases, but also the elastic body may eventually be damaged.

[0005]

The present invention has been made in view of such conventional technical problems, and has the following configuration. According to the configuration of the invention of claim 1, the head portion 14p of the screw head 14 arranged in order from the front end side,
It has a shaft portion 14r, an annular valve seat 11a, and a screw body 10, and has an inner diameter larger than the outer diameter of the shaft portion 14r and is fitted onto the shaft portion 14r. A backflow prevention ring 12 that forms a passage 20 and is movable in the central axis direction is provided, and separates the backward valve portion 12b of the backflow prevention ring 12 from the valve seat 11a during metering, and the backflow prevention ring during injection. By bringing the backward valve portion 12b of 12 into close contact with the valve seat 11a,
In a backflow prevention device for an injection molding machine in which a molten material passage 20 can be opened and closed, a front end face 12 of the backflow prevention ring 12 is provided.
c or the head portion rear surface 14z at the rear end of the head portion 14p
Portions 12a, 14y extending in the central axis direction from a part of the
The rearward facing valve portion 12b of the check ring 12 contacts the annular valve seat 11a between the rear surface of the screw head 14 and the front surface of the check ring 12 outside the support portions 12a and 14y. Elastic bodies 13 and 23 that urge them to contact
And the pressure of the molten material flowing through the molten material passage 20 acts on the elastic bodies 13 and 23.
It is a backflow prevention device of an injection molding machine, which is suppressed by y. According to the invention of claim 2, the support portion 1
2. The backflow prevention device for an injection molding machine according to claim 1, wherein a plurality of 2a, 14y and elastic bodies 13, 23 are arranged in the circumferential direction.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to FIGS. In FIG. 1, reference numeral 16 denotes a cylinder of an injection molding machine. Inside the cylinder 16, a screw main body 10, a pusher 11 having a valve seat 11a, and a screw head 14 are incorporated so as to be movable back and forth and rotatably. The screw head 14 includes a head portion 14p, a support portion 14q, and a neck portion 14 that is a shaft portion in order from the front side.
r, the screw extension 14s, and these gradually decrease in diameter. On the rear side of the screw extension portion 14s, the screw portion 14t
Are formed.

Accordingly, the first head rear surface 14u is formed between the head portion 14p and the support portion 14q, and the support portion 14q is formed.
And a neck portion 14r, a second head portion rear surface 14v is formed, and an annular support surface 14w is formed between the neck portion 14r and the screw extension portion 14s. The screw portion 14t of the screw head 14 and the front end portion of the screw body 10 are screwed together, and the presser metal 11 is sandwiched and fixed between the annular support surface 14w of the screw head 14 and the tip end surface of the screw body 10.
From the front end side of the injection molding machine, screw head 14, pusher 1
1. The screw body 10 is integrated in this order.

A backflow prevention ring 12 having an inner diameter larger than the outer diameter of the neck portion 14r is fitted onto the neck portion 14r to form a molten material passage 20 between the backflow prevention ring 12 and the neck portion 14r. . The backflow prevention ring 12 is
As shown in FIGS. 2 and 3, the front end face 12c has a cylindrical shape.
And a rearward facing valve portion 12b on the inner peripheral portion of the rear end.
The length in the central axis direction between 2c and the backward valve portion 12b is shorter than the length in the central axis direction between the rear surface 14v of the second head portion and the valve seat 11a of the pusher 11, and the neck portion in the cylinder 16 It is possible to move back and forth with respect to 14r. The backward valve portion 12b of the check ring 12
Has a shape compatible with the valve seat 11a of the pressing metal plate 11 facing each other. Accordingly, the backflow prevention ring 12 is retracted, and the inner peripheral portion of the backward valve portion 12b is brought into close contact with the valve seat 11a, so that the molten material passage 20 is shut off, and the backward valve portion 1 is provided.
In the state where the backflow prevention ring 12 is moved forward by the pressure of the molten material on the outer peripheral portion of 2b and the backward valve portion 12b is separated from the valve seat 11a, the screw body 10 side and the reservoir portion 25 side pass through the molten material passage 20. Connect through.

The front end surface 12 of the backflow prevention ring 12
A support portion 12a extending in the central axis direction is formed from a part of c. That is, the support portion 12a is the backflow prevention ring 12
A plurality of (four in the present embodiment) are formed on the front end face 12c at predetermined intervals in the circumferential direction, and each protrudes forward from the front end face 12c. Each of the support portions 12a includes a support portion 12a.
Has a hole 12d that is open to the front surface and extends in the direction of the central axis. The protrusion length of the support portion 12a in the direction of the central axis is such that the rearward facing valve portion 12b is in close contact with the valve seat 11a and the second head portion rear surface 14v is located in the middle portion of the support portion 12a as shown in FIG. Thus, a predetermined gap is set between the front end surface of the support portion 12a and the rear surface 14u of the first head portion, and the above-described back-and-forth reciprocating movement of the backflow prevention ring 12 is allowed.

The head portion 14p and the backflow prevention ring 12
And a plurality of elastic bodies 13 that urge the check ring 12 toward the valve seat 11a. Specifically, the elastic body 13 has its rear end portion inserted into the hole 12d of each support portion 12a, and its front end portion provided with the first end of the screw head 14.
Each hole 1 formed in the circumferential direction on the rear surface 14u of the head portion 1
It is inserted in each 4x. Each elastic body 13 is composed of a compression coil spring, and in a free state in which no external pressure acts on the backflow prevention ring 12 from the front or rear, as shown in FIG. 1, the backward valve portion 12b of the backflow prevention ring 12 has a valve seat 12b. 1
The elastic biasing force is set so as to be in close contact with 1a. The elastic body 13 can also be configured by a disc spring, a wave spring, or the like.

When the backflow prevention ring 12 receives a pressure from the head portion 14p, the backflow prevention ring 12 is assisted by the elastic biasing force of the elastic body 13 and the backward valve portion 1 of the backflow prevention ring 12 is supported.
2b quickly and surely adheres to the valve seat 11a, shuts off the molten material passage 20, and satisfactorily blocks the flow in the molten material passage 20 from the head portion 14p side toward the screw body 10. When pressure is applied from the screw body 10 side,
The elastic body 13 is elastically compressed and deformed, and the backflow prevention ring 12 is formed.
The rearward facing valve portion 12b is separated from the valve seat 11a, and the front end surface 12c of the check ring 12 and the second end of the screw head 14 are separated.
The molten material passage 20 is left open between the rear surface 14v of the head portion and the flow of the molten material forward from the valve seat 11a is allowed.

Next, the operation of the above embodiment will be described. The screw body 10 in the cylinder 16 is rotated by a rotating mechanism (not shown), and the molten material is transferred to the front end portion of the screw body 10 by thrust while heating, melting and kneading the molten material. The molten material is, for example, a metal having a low melt viscosity such as magnesium, aluminum, zinc and lead, an alloy thereof, glass or the like. Cylinder 16 and screw body 1
As shown in FIG. 4, the molten material between 0 and 0 is the backward valve portion 1 of the backflow prevention ring 12 that protrudes from the pusher 11 in the outer diameter direction.
It acts on the outer peripheral portion of 2b to advance the backflow prevention ring 12. As a result, the valve seat 11a and the backward valve portion 12b are separated from each other, so that the molten material flows into the molten material passage 20 from this interval, and the front end surface 12c of the check ring 12 and the rearward facing first portion of the screw head 14 are moved. 2 head rear surface 14v
Between the front end face 12c and the second head portion rear face 1 shown in FIG.
4v ′ and a gap δ), and then passes between the head portion 14p and the inner peripheral surface of the cylinder 16, and the screw head 1
It gradually accumulates in the reservoir 25 on the front side of 4. When the backflow prevention ring 12 advances, the elastic body 13 elastically compressively deforms. The movement of the backflow prevention ring 12 in the direction of the central axis is guided by the inner surface of each supporting portion 12a sliding on the outer peripheral surface of the supporting portion 14q.

In this way, the front end face 12c of the backflow prevention ring 12 and the rear face 14 of the second head portion of the screw head 14 are
The pressure of the molten material flowing between v and
Since the periphery of 3, particularly the inner side in the radial direction of the elastic body 13 is covered with the support portion 12a, it does not act directly on the inner surface of the elastic body 13. Therefore, the elastic body 13 is favorably suppressed from being curved and deformed. In particular, the elastic body 13
Is inserted into the hole 12d of the support portion 12a, and the front end portion of the support portion 12a is positioned on the support portion 14q even when the backward valve portion 12b is in close contact with the valve seat 11a. The structure is such that the pressure of the molten material hardly acts on the elastic body 13.

The rear end portion of the elastic body 13 has the support portion 1
2a is inserted into each hole 12d, and the front end is inserted into each hole 14x formed in the screw head 14. Then, when the backflow prevention ring 12 advances, the elastic body 13
Is not excessively compressed, and the damage of the elastic body 13 is suppressed. When the backflow prevention ring 12 moves forward to form a predetermined gap between the valve seat 11a and the backward valve portion 12b, the front end surface of the support portion 12a has the first head portion rear surface 14 formed.
If the elastic body 13 is configured to come into contact with u, it is possible to prevent the elastic body 13 from being excessively compressed. Then, the screw main body 10 receives the pressure of the molten material in the reservoir 25 or is forced to retract according to the amount of the molten material in the reservoir 25.

Since the screw head 14 and the backflow prevention ring 12 are connected by the elastic body 13, they do not rotate relative to each other. Therefore, in order to prevent the rotational force of the backflow prevention ring 12 from acting on the elastic body 13, the support portion 12 a of the backflow prevention ring 12 is attached to the screw head 14.
With the engaging recess formed in the outer peripheral portion of the support portion 14q, the guide ring is guided to move in the direction of the central axis of the backflow prevention ring 12, and the backflow prevention ring 12 rotates together with the rotation of the screw head 14. The prevention device can also be configured. In addition, the tip of the elastic body 13 is attached to the hole 14
If it is arranged so as to be slidable with respect to the rear surface 14u of the first head portion formed in an annular shape instead of being inserted into x, the non-rotating backflow prevention device in which the backflow prevention ring 12 relatively rotates when the screw head 14 rotates. Is configured.

Thus, when a predetermined amount of the molten material has accumulated in the reservoir 25, the limit switch or the like is operated to stop the screw body 10 and the plasticizing and measuring process of the molten material is completed.

Next, in the injection process, when the screw main body 10 is advanced by the action of a hydraulic cylinder or the like mounted on the rear portion, the molten material accumulated in the reservoir 25 is formed at the front end portion of the cylinder 16. At the same time as being ejected to the outside from a nozzle (not shown), it tries to flow backward through the molten material passage 20.

In such a case, generally, the backflow prevention ring 12 retracts under the pressure of the molten material, and the backward valve portion 1
The molten material passage 20 is blocked by the contact of 2b with the valve seat 11a to prevent the molten material from flowing backward. However, in the case of low-melting materials such as low melting point alloys and glass,
The relative force that pushes back the anti-reflux ring 12 is small, the backward movement of the anti-reflux ring 12 is delayed, and the weighing tends to be inaccurate.

Therefore, when the molten material in the molten material passage 20 flows backward, in addition to the pressure from the head portion 14p, the elastic biasing force of the elastic body 13 acts to prevent the backflow prevention ring 12.
Is pushed back, the backward valve portion 12b of the check ring 12 quickly comes into close contact with the valve seat 11a, and the molten material passage 2
0 is cut off. As a result, the flow from the head portion 14p toward the screw body 10 is blocked at an early stage, and inaccurate metering of the molten material is satisfactorily prevented. In particular, by disposing a plurality of elastic bodies 13 at predetermined intervals in the circumferential direction, the return movement of the backflow prevention ring 12 is smoothly performed. In addition, the molten material can be passed through the molten material passage
Backflow to the screw body 10 side is suppressed, so that molding conditions such as injection speed, ejection force and holding pressure are accurately transmitted to the molded product, such as sink marks, voids, short shots and weld lines. The molding defects of (1) are satisfactorily suppressed, and the molded product is prevented from becoming a defective product.

FIG. 5 shows another embodiment of the present invention, in which the substantially same functional parts as those in the above-mentioned one embodiment are designated by the same reference numerals and the description thereof will be omitted. In this embodiment, the support portion 14q of the screw head 14 is omitted, and the first head portion rear surface 14u and the second head portion rear surface 1 are provided.
Instead of 4v, a rearward facing head portion rear surface 14z is formed at the front end of the neck portion 14r. Instead of the support portion 12a of the backflow prevention ring 12, a plate-shaped support portion 14y extending rearward from a part of the head portion rear surface 14z between the head portion 14p and the neck portion 14r is formed. Further, between the head portion rear surface 14z and the front end surface 12c, as an outer side in the radial direction from each support portion 14y, an elasticity formed of a compression coil spring having the same elastic biasing force as in the above-described first embodiment. The body 23 is arranged. This elastic body 2
3 and the support portion 14y are arranged to face each other in the radial direction.

The protrusion length of the support portion 14y in the direction of the central axis is such that the rear end portion of the support portion 14y is located in the internal space of the backflow prevention ring 12 when the backward valve portion 12b is in close contact with the valve seat 11a. Is set.

According to the other embodiment, as in the case of the above-described first embodiment, the backward valve portion 12b of the check ring 12 is separated from the valve seat 11a at the time of metering, and the check ring 12 at the time of injection. The rearward facing valve portion 12b is the valve seat 11a.
Stick to. When the backward valve portion 12b and the valve seat 11a are separated, the elastic body 23 is compressed and deformed, and
When the rearward facing valve portion 12b comes into close contact with the valve seat 11a, the elastic body 2
The backflow prevention ring 12, which receives the elastic force of 3, quickly retreats. Therefore, the same effect as in the above-described first embodiment can be obtained, such as accurate measurement of the molten material.

[0023]

As can be understood from the above description,
The backflow prevention device for an injection molding machine according to the present invention has the following advantages. The action of closing the molten material passage at the time of injection is promptly performed by being assisted by the elastic force of the elastic body, and not only for the molten material made of resin but also for the molten material such as metal having a low melt viscosity. , It became possible to obtain molded products with stable quality.

In addition, by disposing the supporting portion inside the elastic body, the supporting portion suppresses the pressure of the molten material flowing in the molten material passage acting on the elastic body.
As a result, damage to the elastic body is suppressed, and the durability of the elastic body and the reliability of the backflow prevention device are significantly improved.

[Brief description of drawings]

FIG. 1 is a half sectional view showing a backflow prevention device according to an embodiment of the present invention.

FIG. 2 is a front view showing a backflow prevention ring.

FIG. 3 is a side view showing the backflow prevention ring by partially cutting it out.

FIG. 4 is a similar operation explanatory diagram.

FIG. 5 is a half sectional view showing a backflow prevention device according to another embodiment of the present invention.

[Explanation of symbols]

10: screw body, 11: pusher plate, 11a: valve seat, 1
2: Backflow prevention ring, 12a: support part, 12b: backward valve part, 12c: front end face, 13, 23: elastic body, 14: screw head, 14p: head part, 14q: support surface, 1
4r: neck part (shaft part), 14s: screw extension part, 14
t: screw portion, 14u: rear surface of the first head portion, 14v: second
Rear part of head part, 14y: support part, 14z: rear part of head part, 20: molten material passage, 25: reservoir part.

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-7-256715 (JP, A) JP-A-6-297519 (JP, A) JP-A-2-16529 (JP, A) 106022 (JP, U) Actual Kaihei 1-175809 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) B29C 45/00-45/84 B22D 17/20

Claims (2)

(57) [Claims] 1. A head part (14p) of a screw head (14), a shaft part (14r), an annular valve seat (11a) and a screw body (10) which are arranged in order from the front end side, and the shaft part (14p). 14r) has an inner diameter larger than the outer diameter, and is fitted onto the shaft portion (14r), and a molten material passageway (20) is formed between the shaft portion (14r) and the shaft portion (14r) so as to be movable in the central axis direction. A backflow prevention ring (12) is provided to separate the backward valve portion (12b) of the backflow prevention ring (12) from the valve seat (11a) at the time of metering, and the backward flow of the backflow prevention ring (12) at the time of injection. In a backflow prevention device for an injection molding machine, in which a molten material passage (20) can be opened and closed by bringing a valve portion (12b) into close contact with the valve seat (11a), a front end face (12) of the backflow prevention ring (12).
c) or a support part (1) extending in the central axis direction from a part of the head part rear surface (14z) at the rear end of the head part (14p).
2a, 14y) and outside the support portion (12a, 14y) between the rear surface of the screw head (14) and the front surface of the backflow prevention ring (12).
2) An elastic body (13, 23) for urging the backward valve portion (12b) so as to contact the annular valve seat (11a) is provided, and the pressure of the molten material flowing through the molten material passage (20) is The elastic member (13, 23) acts on the support portion (12a,
14y) to suppress the backflow of the injection molding machine. 2. The backflow prevention device for an injection molding machine according to claim 1, wherein a plurality of support portions (12a, 14y) and elastic bodies (13, 23) are arranged in the circumferential direction.