JP2003062879A - Backflow preventing device for injection molding machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a backflow preventing device which prevent a backflow of a molten resin, in a plasticizing step and a suck back or an injection step and is hardly subjected to design restrictions through widening a molten resin passage. SOLUTION: A valve seat 10a coming into contact with a seat 2a at a tip part or a seat 42b at a head part 41 using the positions of a screw head 40 and a check ring 10 which allows passage of a small diameter part 43 through the ring 10 and is movable in the axial direction, is provided on the screw 1 and the head part 41 side. Inside the valve seat 10a, a cam hole 11 is formed by first to third sliding follow-up parts 12 to 14, and the head 41 has a cam click 18 which collaborates with the cam hole 11. When the screw 1 is rotated forward, the cam click 18 comes into contact with the first and the second follow-up part 12 and 13 of the cam hole 11 and thereby the check ring 10 is driven in the axial direction. Further, the valve seat 10a of the check ring 10 is left apart from the seat 42b and thus freed. When the screw 1 is reversed, the cam click 18 comes into contact with the third sliding follow-up part 14 and in turn, the check ring 10 is driven backward and the rear valve seat 10a of the check ring 10 is closed by the seat 2a at the tip of the screw 1. The cam hole 11 has a locking part 17 for maintaining such a state that the seat 2a closes the molten resin passage.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a screw head mounted on the tip of a screw provided in a heating cylinder so as to be rotatable and axially driven, and a small-diameter portion of the screw head. An annular non-return ring, which is inserted between the tip of the screw and the head of the screw head and is movable in the axial direction, the inner peripheral surface of the non-return ring. The present invention relates to a backflow prevention device in an injection molding machine, in which a resin passage having a predetermined cross-sectional area is formed between the outer peripheral surface of the small diameter portion of the screw head.

[0002]

2. Description of the Related Art An injection molding machine is well known in the art without mentioning a literature name, and roughly includes a heating cylinder and a screw provided in the heating cylinder so as to be driven in a rotational direction and an axial direction. It consists of Such an injection molding machine can be roughly classified into an injection molding machine having a check ring and an injection molding machine having no check ring, depending on the type of screw. Further, when distinguished from the non-return ring, it is divided into a non-rotating type that rotates together with the screw and a non-rotating type that does not interlock with the rotation of the screw.

FIG. 5 (a) shows the main part in the vicinity of a conventional revolving type screw head. That is, this injection molding machine comprises a heating cylinder 50 and a screw 51 provided inside the heating cylinder 50 so as to be drivable in the rotational direction and the axial direction. A pusher 52 is attached to the tip of the screw 51 to attach the screw head 53.
Is attached to the tip of the screw 51 with a screw. A check ring 54 is attached to the shaft of the screw head 53. A conical seat 55 is formed in front of the pusher 52, and an inverted conical valve seat 56 is formed at the rear end portion of the check ring 53 corresponding to the seat 55. Further, a groove 57 is formed at the tip of the check ring 54 by being cut out to a predetermined depth in the axial direction. A pin 58 fixedly attached to the screw head 53 is loosely fitted in the groove 57. Therefore, the screw 51
When the is driven to rotate, the check ring 54 is also driven to rotate. There is a predetermined gap between the outer peripheral surface of the shaft portion of the screw head 53 and the inner peripheral surface of the check ring 54, and a resin passage 59 for molten resin is secured.

An example of a non-circulation type injection molding machine is shown in FIG. 5 (b). Although the same components as those of the rotating type shown in FIG. 5 (a) are designated by the same reference numerals and duplicate description will not be given, the present injection molding machine uses the non-return ring 5
After mounting the 4 ', the screw head 53 with the dowel 53' is fixed to the tip of the screw 51 with a screw. The screw head 53 and the check ring 54 are not mechanically related to each other. Therefore,
Even if the screw 51, that is, the screw head 53 is rotationally driven, the check ring does not rotate.

Next, the operation of the above conventional example will be described. In the plasticizing step, the resin material is supplied to the heating cylinder 50 and the screw 51 is rotationally driven. Then, the resin material is plasticized as is conventionally known, and the check ring 54 is pushed forward by the pressure of the molten resin to be plasticized. As a result, the valve seat 56 of the check ring 54 is separated from the seat 55 of the pusher 52, and the resin passage is secured. As a result, the molten resin is sent to the reservoir 50 'at the tip of the screw head 53. At this time, the non-return type check ring 54 is rotationally driven together with the screw 51 via the pin 57. The pressure of the molten resin stored in the reservoir 50 ′ causes the screw 51 to retract, accumulate a predetermined amount, and complete the plasticizing process.

Depending on the type of resin material used, such as low-viscosity resin material, molding conditions, etc., so-called suck back is carried out after the plasticizing step, that is, the screw 51 is moved rightward or backward in FIG. 5 without rotating. As a result, the resin pressure on the reservoir 50 'side is reduced, and the molten resin flows out from the tip of the injection nozzle when the mold is opened and when the injection nozzle attached to the tip of the heating cylinder 50 is retracted. It is possible to prevent drooling, that is, the dripping phenomenon.

Next, the injection process is started. The screw 51 is driven to the left in FIG. Then, the reservoir 5
The resin pressure of 0'increases to push the check rings 54, 54 'to the right, and the valve seat 56 of the check rings 54, 54' pushes the presser plate 5
Sit on the second seat 55. As a result, the molten resin on the side of the reservoir 50 'is injected and filled into the mold which is clamped with a predetermined amount of the molten resin without leaking to the screw 51 side. A molded product is obtained by opening the mold after cooling and solidification.

As described above, the conventional non-return rings 54, 5
A molded product can be obtained also by an injection molding machine equipped with 4 ', and the co-rotating check ring 54 has an effect of scraping off the molten resin adhering to the inner peripheral wall of the heating cylinder 50, Also, the reservoir 50 'of the check ring 54
There is also an advantage that the structure is simplified because the movement toward the side is restricted by the pin 58. On the other hand, according to the non-circulation type check ring 54 ', the wear resistance of the outer peripheral surface of the check ring 54' is excellent, and the gap between the inner peripheral surface of the heating cylinder 50 and the outer peripheral surface of the check ring 54 'is excellent. Therefore, the effect of reducing the amount of molten resin flowing back can be obtained.

However, the above-described conventional backflow prevention device has a drawback that a part of the molten resin flows back or leaks in an undesired direction. That is, the first drawback is that the pressure on the screw 51 side is high during the period from completion of plasticization to the start of injection, so that a force pushing the check rings 54, 54 ′ to the left acts and the valve seat 56 thereof is acted. Has a drawback that it is separated from the seat 55 of the presser 52 and flows backward from the screw 51 side to the reverser 50 'side. This state is shown in FIG. Secondly, as shown in FIG. 6 (b), the pressure on the reservoir 50 ′ side is high during injection, so that the valve seats 56 of the check rings 54, 54 ′ are locked by the pusher 52. Although the backflow does not occur after it is seated on the seat 55, the molten resin flows back from the start of injection until the valve seat 56 of the check ring seats on the seat 55 of the pusher 52. The third drawback is (c) in FIG.
As shown in FIG. 5, the leakage occurs from the gap between the inner peripheral surface of the heating cylinder 50 and the outer peripheral surfaces of the check rings 54 and 54 ′. Fourthly, as shown in (d) of FIG. 6, after the suck back step, the reverse flow is made from the screw 51 side to the reservoir 50 ′ side. Because there is frictional resistance between the inner peripheral surface of the heating cylinder 50 and the inner peripheral surfaces of the check rings 54, 54 ', when the screw 51 is retracted, the check rings 54, 54' are screwed together. It remains without completely following the backward movement of. Moreover, the screw 51
, The pressure on the reservoir 50 'side is forcibly reduced, and the high-pressure molten resin on the screw 51 side easily flows back to the reservoir 50'.

For the above-mentioned No. 3 backflow, the non-circulation type check ring 54 'as shown in FIG. 5 (b) is applied, the inner peripheral surface of the heating cylinder 50 and the check ring 54. 5,
It can be suppressed to some extent by optimizing the gap between the outer peripheral surface of 4'and improving the working accuracy. However,
The first, second and fourth backflows cannot be avoided by the structure of the conventional backflow prevention device described above.

When such a backflow occurs, the amount of the molten resin material filled in the injection process becomes unstable, and the main factors that cause deterioration of the quality of the molded product such as weight fluctuation of the molded product, short shots, burrs and the like. Becomes Therefore, Japanese Patent Publication Sho-59-479
79, JP-A-62-19423, JP-A-4
-86232, JP-A-4-119812, JP-A-4
A large number of backflow prevention devices have been proposed in Japanese Patent No. 351518, Japanese Patent No. 3017081, Japanese Patent Laid-Open No. 11-34128, Japanese Patent No. 2966779, and the like.

The backflow prevention device disclosed in the above publication is one in which the check ring is positively seated on the seal ring provided at the tip of the screw. Among such backflow prevention devices, As the prior art of the present invention, Japanese Patent Laid-Open No.
-351518 gazette and the patent 3017081 specification can be mentioned. The former JP-A-4-351518
In the backflow prevention device shown in No. 3, a seal ring provided at the tip of the screw, a check ring provided axially movably in front of the seal ring, and the check ring are attached to the screw. It consists of a screw head that is fixed to the tip. A locking groove is formed at a position facing the check ring of the screw head, and a claw having a tapered surface facing the inside of the locking groove is formed on the check ring. Therefore, when the screw is rotationally driven in the forward rotation direction to be plasticized as is conventionally known, and when the screw is rotationally driven in the reverse direction after completion of plasticization, the end of the locking groove of the screw head becomes the claw of the check ring. Abut the formed tapered surface and push the check ring toward the seal ring of the screw. As a result, the rear end of the check ring is seated on the seal ring, and the molten resin in the reservoir or metering chamber is prevented from flowing back toward the screw during the injection process.

On the other hand, the backflow prevention device described in Japanese Patent No. 3017081 also has a seal ring provided at the tip of the screw, and moves axially forward of the seal ring, as in the above-mentioned backflow prevention device. It is composed of a ring-shaped check ring that is freely provided, a screw head that holds the ring-shaped check ring at the tip of the screw, and the like. A plurality of grooves extending in the axial direction are formed on the circumferential surface of the small diameter portion of the screw head. Further, an arcuate projection piece corresponding to the groove is formed in front of the annular check ring. Therefore, when the screw is driven to rotate in the forward direction, the main body of the screw head hits the arcuate protrusion. Since the position where the resin is rotated and hit in the positive direction is the position where the reservoir side and the screw side communicate with each other, it is possible to plasticize the resin material in a conventional manner by continuing the rotational driving of the screw. I can. Further, when the screw is driven to rotate in the opposite direction by a predetermined amount after completion of plasticization, the main body of the screw head again hits the arcuate protrusion. This hit position is the position where the reservoir side and the screw side are closed this time. As a result, the suck back for driving the screw backward or the screw can be axially driven for injection.

[0014]

As described above, the above-mentioned conventional backflow preventing device can also plasticize the resin material and prevent the backflow of the molten resin during the injection / pressure holding process. In the conventional backflow prevention device, various improvements or problems are recognized. For example, the former backflow prevention device exists on the screw side when the reverse rotation is stopped even if the check ring is retracted by the taper surface formed on the claw by rotating the screw reversely and seated on the seal ring. Since the high resin pressure exerted on the check ring pushes the check ring forward, the check ring may move forward along the tapered surface and separate from the seal ring. When separated, the backflow prevention effect is lost. Also, when suck back is performed after the plasticization is completed, there is a frictional resistance between the inner peripheral wall of the heating cylinder and the outer peripheral wall of the check ring, so that the check ring follows the screw even if the screw is retracted. If this is not possible, the non-return ring may stay in its position and separate from the seal ring. Thus, the conventional backflow prevention device has an uncertain surface in the closing operation.

On the other hand, in the backflow prevention device described in the latter Japanese Patent No. 3017081, the molten resin that has passed through the groove during plasticization is placed between one arcuate projection piece and the other arcuate projection piece. Since it is pushed out toward the reservoir through the formed resin flow path, the cross-sectional area of the resin flow path is small, and the flow resistance when passing through the resin flow path increases and the temperature may rise. There is. As a result, a resin burning phenomenon, a surging phenomenon, or the like may occur depending on the type of resin used. Also, since such a phenomenon occurs,
It is difficult to apply as a backflow prevention device for a small injection molding machine in which the cross-sectional area of the resin flow path cannot be widened. Moreover,
There is also a risk that the positional relationship of the resin flow paths will shift at a delicate angle on the circumference, and the cross-sectional area of the resin flow paths will change. For example, due to the pressure of the molten resin flowing from the screw side in the plasticizing process, the check ring and the arc-shaped protrusion immediately come into close contact with each other and are pressed against the screw head, and the check ring, the arc-shaped protrusion and the screw head are integrated. There is a possibility that it will be turned around. In such a state, the resin passage is incompletely opened, and the cross-sectional area of the resin passage is small. Therefore, as described above, resin burning, surging, etc. suddenly occur, resulting in deterioration of the quality of the molded product. Also, when the screw is rotated in the reverse direction before performing the injection process, there is a possibility that a similar angular deviation may occur, and as a result, the resin flow path is incompletely closed. Then, backflow of the molten resin occurs, and future molding defects such as short shots and sink marks will occur. There is also a problem that the number of constituent members is relatively large, the structure is complicated and the cost is high, and further, restrictions are likely to occur when designing with a small size or improved durability.

An object of the present invention is to provide a backflow prevention device that solves the above-mentioned problems, and specifically, the backflow of the molten resin is prevented during the plasticizing step and during the suckback or injection step. More completely prevented, yet simple structure, the resin passage of the molten resin is relatively large,
It is an object of the present invention to provide a backflow prevention device that is less likely to be restricted by design.

[0017]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a structure in which a check ring is formed in a screw or a component of a screw head regardless of whether the check ring is driven backward or forward. A valve seat for seating on the seat seat is provided. Also, when driving the screw to rotate,
The check ring is configured to be forced axially to move the valve seat away from or seat against the seat. Furthermore, it is also configured to maintain a seated state. It is also configured to combine a plurality of backflow prevention devices. That is, in order to achieve the above-mentioned object, the invention according to claim 1 is a screw head attached to the tip of a screw provided inside the heating cylinder so as to be drivable in the rotational direction and the axial direction. , An annular check ring that is axially movably provided between the tip of the screw and the head of the screw head while being inserted into the small-diameter portion of the screw head.
A backflow prevention device in which a resin passage having a predetermined cross-sectional area is formed between an inner peripheral surface of the check ring and an outer peripheral surface of a small diameter portion of the screw head, wherein the check ring includes a screw A rear valve seat seated on the seat seat at the tip end and a front valve seat seated on the seat seat at the head part are formed, and a cam hole made up of a plurality of different-sliding slide follower parts is formed inside. In addition, the screw head is provided with a cam pawl that cooperates with the cam hole, and when the screw is rotationally driven in the forward direction, the cam pawl comes into contact with a predetermined sliding follow-up portion of the cam hole to cause the reverse movement. When the stop ring is driven in the axial direction, both valve seats of the check ring are separated from the both seat seats to be in an open state, and are rotationally driven in the opposite direction,
The check ring is driven in the axial direction by abutting against another slip follower, and one of the valve seats of the check ring is seated on the seat seat at the tip of the screw or the seat seat of the head. Configured to be closed. According to a second aspect of the present invention, the screw head is mounted inside the heating cylinder so as to be drivable in the rotation direction and the axial direction, and is attached to the tip end portion of the screw. The screw head is inserted into the small diameter portion of the screw head. A plurality of annular check rings that are movably provided between the tip of the screw and the head of the screw head in a direction toward each other and in a direction away from each other. A backflow prevention device in which a resin passage having a predetermined cross-sectional area is formed between an inner peripheral surface of a check ring and an outer peripheral surface of a small diameter portion of the screw head, wherein the check ring has a tip end of the screw. A rear valve seat for seating on the seat seat of the head part and a front valve seat for seating on the seat seat of the head part are formed, and the inside of the seat seat seat of the head part is slid following a plurality of different inclinations across the plurality of check rings. From the department A cam hole is formed, and a cam claw that cooperates with the cam hole is provided in the screw head. When the screw is rotationally driven in the positive direction, the cam claw causes the cam claw to follow a predetermined slip follow-up portion. Abutting against and driving the check rings toward each other, both valve seats of the check ring are separated from the both seat seats and are in an open state,
When it is rotationally driven in the opposite direction, it comes into contact with another slip follower to drive the check rings in a direction in which they are separated from each other, and both valve seats of the check ring are seated at the tip of the screw and the head part. It is configured to be seated on the seat seat of and closed. According to a third aspect of the invention, the screw head is mounted inside the heating cylinder so as to be drivable in the rotation direction and the axial direction, and is attached to the tip end portion of the screw, and the screw head is inserted into the small diameter portion of the screw head. A plurality of annular check rings movably provided between the tip portion of the screw and the head portion of the screw head in a direction away from each other and a direction approaching each other; And a seal ring provided on the small diameter portion of the screw head so as to be interposed between the check rings, and between the inner peripheral surface of the check ring and the outer peripheral surface of the small diameter portion of the screw head. A backflow prevention device in which a resin passage having a predetermined cross-sectional area is formed, wherein the plurality of check rings include:
A rear valve seat which is seated on one seat seat of the seal ring and a front valve seat which is seated on the other seat seat are respectively formed, and a cam hole formed of a plurality of slide following parts is formed on the side part. In addition, the screw head or the screw is provided with a cam claw that cooperates with the cam hole, and when the screw is rotationally driven in the positive direction, the cam claw comes into contact with a predetermined slide following portion of the cam hole. Driving the check rings in a direction away from each other, the valve seats of the plurality of check rings are separated from the seat seats of the seal ring to be in an open state, and are rotationally driven in the reverse direction,
The valve seats of the plurality of check rings are seated on the seat seats of the seal rings to be in a closed state by abutting against another slip follower and driving the plurality of check rings toward each other. The lock portion for maintaining the closed state in which the valve seat of the check ring is seated on the seat seat in the cam hole according to any one of claims 1 to 3. The invention according to claim 5 is provided with
4 is a combination of the backflow prevention device according to any one of 4 and another backflow prevention device, wherein the other backflow prevention device has an outer peripheral surface relatively closely contacting the inner peripheral surface of the heating cylinder. It consists of an annular check ring that is movably provided in the axial direction regardless of the rotation of the screw, and the inner peripheral surface of the check ring and the outer peripheral surface of the shaft portion through which the check ring is inserted. And a resin passage having a predetermined cross-sectional area is formed between and, and a valve seat for seating on a seat seat formed on a component of the screw head is formed at an end of the check ring. The invention according to claim 6 is characterized in that, between the front valve seat of the check ring according to any one of claims 1 to 5 and the seat seat of the head portion or the seat seat of the seal ring,
Even when the front valve seat is seated on the seat seat, there is some clearance. In the invention according to claim 7, the front valve seat according to any one of claims 1 to 5 is formed with a plurality of notch grooves in which the pressure receiving surface on which the molten resin acts faces the screw side. Has been done.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below. FIG. 1A shows a state in which the resin passage is opened,
And (b) is a cross-sectional view showing a closed state, respectively, but in order to clarify the display of the figure, (a) of FIG. 1 mainly includes reference numerals of components related to the check ring. The reference numerals relating to the screw, the heating cylinder and the heating cylinder will be described by writing them in FIG. First of the present invention
In the backflow prevention device according to the embodiment of the present invention, the annular presser 2 is attached to the tip of the screw 1, the front side of the presser 2, that is, the left side in FIG. 1A or 1B, the axial direction. Non-return ring 1 movably installed
0, a screw head 40 and the like screwed to the tip of the screw 1.

The heating cylinder 3 having a predetermined length in the axial direction is shown in FIG.
Although not shown in the figure, as is well known in the art, a plurality of heaters whose heat generation temperatures are individually controlled are provided on the outer peripheral portion thereof, and an injection nozzle is attached to the tip portion thereof, that is, the left end portion in FIG. The area behind the measuring chamber is the measuring chamber, that is, the reservoir 4. Further, a resin material supply port is opened near the rear side, and a screw drive device is provided at the rear end portion. Inside the heating cylinder 3 configured as described above, the screw 1 having a conventionally known form is provided. The screw 1 is rotationally driven in the forward direction by the drive device in the heating cylinder 3 during plasticization, and is axially driven during injection. The tip surface of the screw 1 driven as described above is a flat vertical surface, and a fitting hole 5 is opened in the axial direction from this surface to a predetermined depth, and a small diameter is provided from the bottom of the fitting hole 5. The female screw 6 is further formed to a predetermined depth. Screw head 4 to this female screw 6
0 male screw is screwed.

The ring-shaped pusher 2 has a ring-shaped seat portion 7
And a cylindrical insertion portion having a smaller diameter than the seat portion 7. The outer diameter of the seat portion 7 is smaller than the inner diameter of the heating cylinder 3, and a resin passage of molten resin having a predetermined cross-sectional area is secured between the outer peripheral surface of the seat portion 7 and the inner peripheral surface passage of the heating cylinder 3. A frustoconical seat 2a is formed on the front portion of the seat 7, that is, on the side of the check ring 10. As will be described later in detail, the rear valve seat of the check ring 10 is seated on the seat seat 2a at the time of injection.

The non-return ring 10 has a tubular shape or an annular shape having a predetermined length in the axial direction, the outer peripheral surface of which is in contact with the inner peripheral surface of the heating cylinder 3 and is movable in the axial direction.
The inner diameter is sufficiently smaller than the outer diameter of the small diameter portion of the screw head 40 described later. This allows the check ring 1
A second resin passage J2 having a predetermined cross-sectional area is formed between the inner peripheral surface of 0 and the outer peripheral surface of the small diameter portion of the screw head 20.
At the rear end portion of the check ring 10 configured as described above, a rear valve seat 10a that is seated on the seat seat 2a of the pusher 2 is formed. As shown in FIG. 1, the rear valve seat 10a is composed of a tapered surface whose diameter is expanded rearward. Seat seat 2 of rear valve seat 10a and pusher 2
A first resin passage J1 is formed between a and a during plasticization.

A front valve seat 10b is formed at the front end of the check ring 10. The front valve seat 10b is composed of a tapered surface whose diameter is reduced rearward. As described above, according to the present embodiment, since the valve seats 10a and 10b are formed at both ends of the check ring 10, even if the check ring 10 is driven rearward or forward, the reverse flow of the molten resin does not occur. Will be prevented.

Non-return ring 1 constructed as described above
A through-hole-shaped cam hole 11 is formed at a substantially central portion in the axial direction of 0. The cam hole 11 cooperates with a cam pawl described later, and as shown in FIG. 1A, the first to third slip follower portions 1 are associated with the rotation direction of the screw 1.
2-14, and the direction which crosses the non-return ring 10 from the upper end part of the 1st and 3rd slip follower parts 12 and 14, ie, (a) of FIG.
The first and second straight line portions 1 extending linearly upward in
5 and 16 are formed as closed holes.
The first and second slip followers 12, 13 are provided in the screw head 4
When 0 is rotationally driven in the plasticizing direction, it contacts the cam claws and drives the check ring 10 to the open position. The check rings 10 are inclined in opposite directions, and the confluent point, that is, the lower end thereof is the valley v. . When the cam claw hits the valley portion v, the check ring 10 is prevented from moving in an undesired manner in the axial direction. Also, the third
When the screw 1 is rotationally driven in the direction opposite to the plasticizing direction, the slip follower portion 14 contacts the cam claw and the check ring 1
0 to the closed position, the first slip follower 12
It is substantially parallel to and is located above the valley v. Moreover,
The first and second linear portions 15 and 16 extend upward by a predetermined amount to form a lock portion 17.

The screw head 40 has a conical head portion 41, a metal plate 42 behind the head portion 41, a small diameter portion 43 extending rearward from the corresponding metal 42, and the small diameter portion 4.
3 and a shaft portion that extends further rearward, and a male screw 44 that is screwed into the female screw 6 of the screw 1 is formed on the shaft portion. The outer diameter of the dowel 42 is smaller than the inner diameter of the heating cylinder 3, and a resin passage having a predetermined cross section is secured between them. On the rear side of the metal plate 42, a seat seat 42b having a tapered diameter is formed. A third resin passage J3 is secured between the seat seat 42b and the front valve seat 10b of the check ring 10 during plasticization. The outer diameter of the small diameter portion 43 of the screw head 40 is sufficiently smaller than the inner diameter of the check ring 10. Therefore, as described above, the sufficiently large second resin passage J2 is secured between the outer peripheral surface of the small diameter portion 43 and the inner peripheral surface of the check ring 10. The small diameter portion 43 is axially longer than the check ring 10 by a predetermined amount. Therefore, the check ring 10 is axially movable between the presser plate 2 and the stopper plate 42.

The small diameter portion 43 of the screw head 40 constructed as described above is provided with the cam claw 18 in the shape of a pin in the first embodiment. This cam claw 18
Faces the inside of the cam hole 11 to cooperate with the cam hole 11 of the check ring 10, but its top does not protrude from the outer surface of the check ring 10. Therefore, the cam claw 18
There is no possibility that the apex of the above will contact the inner peripheral surface of the heating cylinder 3. The positional relationship between the cam hole 11 and the cam claw 18 is
The relationship is such that the functions and effects described later are achieved.

The backflow prevention device according to this embodiment can be assembled, for example, as follows. That is, the shaft portion 43 of the screw 1 is attached to the dowel 42, the check ring 1
0 and the presser foot 2 are mounted in this order, and the cam claw 18 is attached to the small diameter portion 43 so as to face the inside of the cam hole 11 by applying, for example, a press fit type or a screw type. Next, the male screw 44 of the screw head 40 is screwed into the female screw 6 of the screw 1. As a result, it is assembled as shown in FIG. 1 (a) or (b).

Next, the operation of the first embodiment will be described. When plasticizing resin material, screw 1
Is rotationally driven in the positive direction indicated by arrow A in FIG. Then, the screw head 40 is also driven in the same direction, and the cam pawl 18 provided on the small diameter portion 43 is also driven in the same direction. Even if the screw 1 is rotationally driven, the check ring 10 is stopped due to frictional resistance or the like, so that the cam claw 18 is rotated relative to the first slip follower 12 or the second slip follower 12. It abuts on the slip follower 13. Then, the check ring 10 is axially driven by the reaction so that the cam claw 18 reaches the valley v.
A stable state reaching the valley portion v is shown in FIG. In this state, as shown in the drawing, the check ring 10 is located substantially in the center of the small diameter portion 43 in the axial direction, and the seat seat 2a of the pusher 2 and the rear valve seat 10a of the check ring 10 are in contact with each other.
And a third resin passage J3 between the seat seat 42b of the dowel 42 and the front valve seat 10b of the check ring 10. Below, screw 1
When is rotated in the plasticizing direction indicated by arrow A, the check ring 10 is also driven by the cam pawl 18 in the same direction. Thereby, the effect of scraping the molten resin on the inner peripheral surface of the heating cylinder 3 can be obtained.

The resin material supplied into the heating cylinder 3 from a hopper (not shown) is heat applied from a heater provided on the outer peripheral portion of the heating cylinder 3, frictional action when the screw 1 is rotationally driven, shearing action, etc. Are melted by the heat generated by the
It is pumped and accumulated in the reservoir 4 in front of the screw head 40 through J3. Due to the pressure of the accumulated molten resin,
The screw 1 retracts. Alternatively, it is set back in proportion to the amount of accumulated molten resin. After retreating a predetermined amount, screw 1
Stop the rotation drive of. As a result, a predetermined amount of molten resin is accumulated. The screw 1 is fixed in axial movement or position as is well known in the art.

After the plasticizing step is completed, the screw 1 is rotationally driven in the reverse direction indicated by the arrow B in FIG. 1B by a predetermined amount before the injection step is performed. Then, since there is a frictional resistance between the check ring 10 and the heating cylinder 3, the check ring 10 is in a stopped state, a relative movement occurs between the check ring 10 and the screw head 40, and the cam pawl 18 is moved next time. Contacts the third slip follower 14. Then, the reaction causes the check ring 10 to move to the right in FIG. 1B. As a result, the check ring 10
The rear valve seat 10a of the above seats on the seat seat 2a of the pusher 2.
When driven further, the cam claw 18 enters the lock portion 17.
As a result, the seated state is locked. This locked state cannot be released unless the screw 1 is rotationally driven in the forward direction. If necessary, suck back is performed to force the screw 1 to move backward. At this time, the check ring 10
Since the lock state is maintained and the seated state is maintained, the check ring 10 follows the movement of the screw 1 even if the backward speed of the screw 1 is high, and the reverse flow of the molten resin does not occur.

After the plasticizing step, the screw 1
Is stopped and the engagement state between the cam hole 11 and the cam claw 18 is loosened, so that the cam claw 18 is also moved to the third slip follower unit 1.
It is a short time until the check ring 10 comes into contact with the check ring 10.
Is free in the axial direction, and further, the check ring 10 has valve seats 10a and 10b formed at both ends.
If there is a difference in the pressure of the molten resin between the reservoir 4 side and the screw 1 side for some reason, the check ring 10 is driven to the lower pressure side. As a result, either the rear valve seat 10a or the front valve seat 10b of the check ring 10 is seated on the seat seat 2a of the pusher 2 or the seat seat 42b of the stopper 42. This prevents backflow or movement of the molten resin to the low pressure side. Further, the friction resistance between the inner peripheral surface of the heating cylinder 3 and the outer peripheral surface of the check ring 10 is reduced due to, for example, wear, and the check ring 10 completes a predetermined locking operation even if the screw 1 is rotated in the reverse direction. Even if not
According to the present embodiment, since the seal portions 10a and 10b are formed at both ends of the check ring 10, the check ring 10 is seated on the seat 2a of the presser 2 due to the pressure difference of the molten resin.
Alternatively, the seat 42 is seated on any one of the seats 42b. As a result, backflow from the completion of plasticization to the start of injection or backflow after suckback is prevented.

Next, the injection process is started. The screw 1 is driven in the axial direction. Then, the molten resin accumulated in the reservoir 4 is injected into the cavity of the mold that has been clamped. A molded product is obtained by holding the pressure, waiting for cooling and solidification, and then opening the mold. When the screw 1 is rotationally driven in the forward direction for the next plasticization, the cam pawl 18 relatively rotates due to the reason described above, and the cam pawl 18 is disengaged from the lock portion 17 and the locked state is released. 18 contacts the second slip follower 13. As described above, the resin passage J1,
J3 is constructed and can be plasticized. Similarly, suck back, injection and the like are performed.

According to the first embodiment, various effects can be obtained. For example, when the screw 1 is rotationally driven in the plasticizing direction, the cam claw 18 moves the first and second slip followers 12, 1
Since it fits in the valley portion v formed by 3, the resin passages J1, J3 are surely
The effect of being secured is obtained. Further, when the rotation of the screw 1 is stopped after the plasticization is completed, the engagement state between the cam claw 18 and the cam hole 11 is loosened, so that there is a pressure difference in the molten resin between the screw 1 side and the reservoir 4 side. The pressure difference drives the check ring 10 in the axial direction, so that either the rear valve seat 10a or the front valve seat 10b of the check ring 10 is seated on the seat 2a or 42b. This prevents the molten resin from flowing back or moving in an undesired direction. Further, when the screw 1 is rotationally driven in the opposite direction after the plasticization is completed, the cam claw 18 fits into the lock portion 17,
The closed state is reliably maintained. Therefore, even if the backward speed of the screw 1 at the time of sucking back is high, the check ring 10 follows and the closed state is maintained. Further, the molten resin does not flow backward from the screw 1 side toward the reservoir 4 after suck back. That is, according to the present embodiment, it is possible to obtain the effect that all but the drawbacks of the conventional backflow prevention device described with reference to FIG.
Furthermore, the first to third resin passages J1 to J3 can be made as large as necessary, and their structure is also simple. Furthermore, even if the check ring 10 does not complete the predetermined locking operation even if the screw 1 is rotated in the reverse direction, according to the present embodiment, the seal portions 10a, 10a, 10c are provided at both ends of the check ring 10.
Since b is formed, the non-return ring 10 is moved to the seat 2a of the pusher 2 or the stopper 42 due to the pressure difference of the molten resin.
To be seated on one of the seat seats 42b. This allows
Backflow from the completion of plasticization to the start of injection or backflow after suckback is prevented.

In the embodiment shown in FIG. 1, one cam hole 11 is shown, but it is also possible to receive a plurality of cam holes 11, for example 2 to 3, at symmetrical positions. Also, cam hole 1
It is obvious that the shapes and structures of 1 and the cam pawl 18 are not limited to the illustrated embodiment. For example, when the screw 1 is rotationally driven in the reverse direction by changing the shape of the cam hole, the front valve seat 10b of the check ring 10 is moved to the metal plate 4
The second seat seat 42b may be seated.

Next, a second embodiment of the present invention will be described with reference to FIG. The same elements as those of the first embodiment described above are designated by the same reference numerals, and similar constituent elements are denoted by the same reference numeral with a dash “′” to avoid redundant description. Further, for the sake of clarity of the drawing, the reference numerals indicating the constituent elements are separately written in (a) and (b) of FIG. According to the second embodiment, the check ring is
The first, which is located on the screw 1 side, is divided into two in a sliced shape.
The non-return ring 20 and a second non-return ring 20 'located in front of the non-return ring 20. The first and second check rings 20 and 20 'are driven in a direction in which they are separated from each other and in a direction in which they approach or come in contact with each other. Therefore, the through-hole-shaped cam hole 21 is formed over the divided surfaces of the first and second check rings 20 and 20 '. The cam hole 21 includes the first and second slip follower portions 22 and 22 ′ located below in FIG. 2, the third and fourth slip follower portions 23 and 23 ′ located above, and the slip follower portions 22. , 23 and 22 ′, 23 ′ and straight line portions 24, 24 ′. When viewed in a plan view, the first and second slip follower portions 22 and 22 ′ cooperate with each other to form a substantially chevron shape, and the third and fourth slip follower portions 2 and 22 ′.
3 and 23 'have a substantially valley shape.

On the other hand, the cam claw 25 mounted so as to face the inside of the cam hole 21 has the first and second slip follower portions 22, 2 of the cam hole 21 when the screw 1 is rotationally driven in the positive direction.
2 ′ respectively, and these first and second slip followers 22, 22 ′ and thus the first and second non-return rings 2
Wing-shaped first and second acting to attract 0, 20 '
Of the first and second check rings 20 and 20 'in the left-right direction, that is, in the front-back direction. It is integrally configured with the convex portion 27 that acts to push it in the direction. Such a cam pawl 25 has a predetermined area when seen in a plan view, and is thus formed to have a substantially arcuate side cross-sectional shape. Further, the surface of the cam claw 25 constitutes a curved surface substantially the same as the outer peripheral surfaces of the check rings 20, 20 ', but is slightly lower.

The backflow prevention device according to the second embodiment also operates in substantially the same manner as the above-described backflow prevention device, so a detailed description will be omitted, but in order to plasticize the screw 1, the screw 1 is shown in FIG. When it is rotationally driven in the forward direction indicated by the arrow A in FIG. 1, the first and second check rings 20 and 20 ′ are stopped for the reason described above, and therefore the cam claw 25
The first and second working portions 26, 26 'of the first and second non-return rings 20, 20' of the first and second non-return rings 20, 20 '.
To the first and second non-return rings 20, 2 respectively.
0's are pulled together. As a result, the rear valve seat 20a of the first check ring 20 is separated from the seat 2a of the presser plate 2, and the front valve seat 20'b of the second check ring 20 'is also seated on the seat 42b of the dowel 42. Away from. Thereby, the resin passages J1 and J3 are formed. At this time, the cam hole 21
The first and second slip follower portions 22, 22 'of the cam claw 25 have a substantially chevron shape, and the first and second action portions 2 of the cam claw 25 are formed in the chevron portion.
6, 26 'come into contact and lock, so that resin passages J1, J3
Is reliably retained. It is plasticized as described above.
When the screw 1 is driven to rotate in the opposite direction after completion of plasticization,
This time, the convex portion 27 of the cam pawl 25 has the third and fourth slip follower portions 2.
3, 23 'Therefore, the first and second check rings 20, 2
Push apart between the 0'division planes. As a result, the first and second
The check rings 20, 20 ′ of the first check ring 20 are driven in directions away from each other so that the rear valve seat 20 a of the first check ring 20 is seated on the seat seat 2 a of the pusher 2 and at the same time, the second check ring 20 ′. The front seat 20'b of'is the seat seat 42 of the dowel 42.
Sit on b. When driven further, the convex portion 2 of the cam claw 25
7 lies completely between the dividing surfaces of the first and second non-return rings 20, 20 '. As a result, the closed state is locked.
This locked state is not released unless the screw 1 is rotationally driven in the forward direction. Like this, it ’s closed in two places,
The locked state is shown in FIG. If necessary, carry out suckback. Then, the injection process is performed.

It is apparent that the same effects as those of the first embodiment described above can be obtained by the second embodiment, but according to the second embodiment, the screw 1 is rotated in the opposite direction. Then, after the first and second check rings 20, 20 ', both front valve seats 20a, 20'b are simultaneously seated in the seat seat 2
It is possible to obtain an effect that the backflow is more reliably prevented by sitting on the a and 42b. It is obvious that the second embodiment can also be modified, for example, the numbers and shapes of the cam holes 21 and the cam claws 25 can be modified.

A third embodiment of the present invention will be described with reference to FIG. In addition, the same reference numerals are attached to the same elements as the constituent elements of the above-described first or second embodiment,
Also, for similar components, a dash "'" is added to the same reference numeral.
Will not be repeated. Also in the third embodiment, the non-return ring is composed of two first and second non-return rings 30 and 30 'which are divided into two in the shape of a slice like the second embodiment. Then, the first and second valve seats 30a, 30'b
Are formed on the divided side. Further, notches 31, 3 for securing a resin passage are provided at the rear end and the front end thereof.
1'is formed. On the rear side and the front side of the first and second check rings 30, 30 ′ configured in this way,
Through-hole-shaped first and second cam holes 32, 32 'with open sides
Are formed. Since these cam holes 32, 32 'and a cam pawl described later are configured in line symmetry, only one component will be described below, and the other will be described by adding a dash "'" to the same reference numeral. To do. First
The cam hole 32 of the first slip follower 33 is located below.
And a second slide following portion 34 located above and a straight portion 35 connecting the lower end portions of these slide following portions 33, 34. These first and second slip follower parts 33,
With respect to the inclination direction of 34, when the cam claw comes into contact with the first slip follower 33, the first check ring 30 is driven in a direction away from the seal ring 50 described later, and the second slip follower 34 is moved. When locked, it is inclined so as to be pushed out in the direction in which it contacts the seal ring 50. The upper part of the second slip follower 34 is linear and has a first cam pawl 60 which will be described later.
The wide linear portion 63r of FIG. 3 functions as an entry stopper, but when it is entered, it also acts as a lock. Therefore, this linear portion serves as the lock portion 36. According to the third embodiment, the seats are not formed on the members 2'and 42 'corresponding to the presser foot 2 and the abutment 42 according to the first and second embodiments.

According to the third embodiment, the cam pawl is composed of two cam pawls, a first cam pawl 60 and a second cam pawl 60 ', and the first and second non-return rings 30, It is provided on each side of 30 '. The first cam claw 60 is the first
Of the first cam hole 32 and the first acting portion 61 that drives the first check ring 30 in the direction of moving away from the seal ring 50 by contacting the first slip follow-up portion 33 of the first cam hole 32. Two
Second action portion 62 that abuts on the slip follower portion 34 and drives the first check ring 30 toward the seal ring 50, and upper and lower linear portions 63 and 64 are integrally formed. ing. A wide straight portion 63r is provided between the first and second acting portions 61 and 62. This straight part 63
When r fits into the lock 36, the closed condition will be maintained. Since the first and second cam claws 60 and 60 ′ according to the third embodiment also have a predetermined area, they are formed so that their cross-sectional shapes are arcuate in side view. Further, the surface thereof is slightly lower than the outer peripheral surfaces of the first and second check rings 30, 30 '.

The first and second cam pawls 60, 60 'thus constructed are, as shown in FIG. 1B, a tubular portion 60 fitted to the shaft portion 43a of the screw head 40'.
It is formed integrally with t and 60't. According to the present embodiment, an annular seal ring 50 is provided between the first and second check rings 30 and 30 '. The outer diameter of the top of the seal ring 50 is smaller than the inner diameter of the heating cylinder 3, and a resin passage is secured between the outer peripheral surface of the top of the seal ring 50 and the inner peripheral surface of the heating cylinder 3. The first and second check rings 30, 30 'of the first and second valve seats 30a, 3'
Tapered first and second seal seats 50 corresponding to 0'b
a and 50'b are formed respectively.

Screw head 4 according to the present embodiment
The reference numeral 0'includes a shaft portion 43 extending from the head portion 41 'in the axial direction to a predetermined length. A male screw 44 is formed at the rear end of the shaft portion 43. Therefore, as shown in FIG. 3B, the second cam pawl 60 ′ and the second check ring 3 are attached to the shaft portion 43a of the screw head 40 ′.
0 ', seal ring 50, first non-return ring 30, first
The backflow prevention device is assembled by inserting or mounting the cam claws 60 in this order and screwing the male screw 44 of the screw head 40 ′ into the female screw 6 of the screw 1.

Since the backflow prevention device according to the third embodiment is also assembled in substantially the same manner as the backflow prevention device according to the first embodiment, the assembly sequence is shown in FIG. 3 (b). No explanation will be given. Further, in terms of operation, since it operates in substantially the same manner as in the second embodiment, detailed description thereof will be omitted, but if the screw 1 is rotationally driven in the forward direction indicated by arrow A in FIG. , First,
The two non-return rings 30, 30 ′ are in a stationary state because there is a frictional resistance with the heating cylinder 3. Therefore, relative movement occurs between the first and second cam claws 60 and 60 ′, and the first action portions 61 and 61 ′ of these cam claws 60 and 60 ′ are moved to the first and second cam claws 60 and 60 ′. First of holes 32, 32 '
To the slip follower parts 33, 33 'of the
The non-return rings 30, 30 'of the first and second cam claws 60, 6
Pull towards 0 '. That is, the first and second check rings 30 and 30 'are driven in the directions away from each other. As a result, as shown in FIG.
The check rings 30, 30 of the valve seats 30a, 30'b of the seal rings 50, 50 ', 50'b of the seal ring 50
Away from. This state is maintained during plasticization.

Therefore, when the screw 1 is continuously driven to rotate in the forward direction, the notch 31 and the first notch 31 formed in the first check ring 30 are plasticized as is well known in the art.
Between the inner peripheral surface of the check ring 30 and the rear small diameter portion 43a, between the first valve seat 30a of the first check ring 30 and the first seal seat 50a of the seal ring 50. Resin passage J'1, second valve seat 3 of second check ring 30 '
0'b and the second seal seat 50'b of the seal ring 50, the resin passage J'3, between the inner peripheral surface of the second check ring 30 'and the second small diameter portion 43'b. Accumulated in the reservoir 4 through the resin passage and the cutout 31 '.

When a predetermined amount is accumulated and the plasticization is completed, the rotational driving of the screw 1 is stopped. Then, the screw 1 is rotationally driven in the opposite direction by a predetermined amount. Then, first,
Since there is a frictional resistance between the two check rings 30, 30 ′ and the heating cylinder 3, these check rings 30, 3 ′ are provided.
0'is a temporary stop state, a relative movement occurs between the screw 1 or the screw head 40, and the second acting portions 62, 62 'of the first and second cam pawls 60, 60' are now in contact with each other. Contacts the second slip follower portions 34, 34 of the first and second cam holes 32, 32 '. Then, and by its reaction, pushes the first and second check rings 30, 30 'towards each other. As a result, the first and second check rings 3
The first and second valve seats 30a and 30'b of 0 and 30 'are seated on the first and second seat seats 50a and 50'b of the seat ring 50, respectively. The state in which the resin passage is seated and closed is shown in FIG. 3 (c). Further, when driven, the wide linear portion 6 of the first and second cam pawls 60, 60 'is
3r and 63'r enter the lock portions 36 and 36 '. As a result, the seated state is locked. This locked state cannot be released unless the screw 1 is rotationally driven in the forward direction. If necessary, suck back is performed to force the screw 1 to move backward.

Then, as described above, the screw 1 is axially driven and injected. Then, a molded product is obtained. It is clear that the same effects as those of the above-described second embodiment can also be obtained by the third embodiment. In addition, also in the present embodiment, the first and second cam holes 32 and 32 ′, the first and second cam holes 32 and 32 ′,
If there is a certain play between the second cam claw 60, 60 ',
After the plasticization is completed, but before the screw 1 is rotationally driven in the reverse direction, if there is a pressure difference in the molten resin between the screw 1 side and the reservoir 4 side, this pressure difference causes the first and second check valves to stop. Valve seat 30a, 30'b of either ring 30, 30 '
Is the first and second seat seats 50a, 50 of the seat ring 50.
It is seated in either of b and backflow is prevented. Further, as described above, the frictional resistance between the inner peripheral surface of the heating cylinder 3 and the outer peripheral surfaces of the first and second check rings 30 and 30 'is reduced due to, for example, wear, and the screw 1 is rotated in the reverse direction. Even if the check rings 30, 30 'do not complete the predetermined locking operation, according to the present embodiment, the seal portions 30a, 30'b are formed on both the first and second check rings 30, 30'. Therefore, the first and second check rings 30 and 30 'are seated on either the first seal seat 50a or the second seat seat 50'b of the seal ring 50 due to the pressure difference of the molten resin. . As a result, backflow from the completion of plasticization to the start of injection or backflow after suckback is prevented.

Finally, the fourth aspect of the present invention will be described with reference to FIG.
An embodiment will be described. According to the embodiment shown in FIG. 4A, a backflow prevention device Y having a conventionally well-known configuration is provided in front of the backflow prevention device X according to the third embodiment.
Are provided in series. Since the backflow prevention device X has been described, the same reference numerals are used for the main constituent elements and the description thereof will be omitted. Only the backflow prevention device Y will be described. The backflow prevention device Y includes a non-turning non-return check ring 70. Then, at the rear end of the check ring 70,
Tapered valve seat 70a seated on 2'seat seat 42b
And a non-return ring 70 is provided on the front end of the stopper 42.
A notch 71 is formed in order to secure a resin passage when it comes into contact with. A resin passage having a predetermined cross-sectional area is secured between the inner peripheral surface of the check ring 70 and the outer peripheral surface of the small diameter portion of the screw head, as in the above embodiment.

Corresponding to the check ring 70, in front of the dowel 42 ', a cylindrical portion 4 fitted on the shaft portion of the screw head 40 ".
2't is integrally formed. The outer diameter of the tubular portion 42't is smaller than the inner diameter of the check ring 70, and
Between the outer circumference of 2't and the inner circumference of the check ring 70,
A resin passage is secured as is well known in the art. To assemble the backflow prevention devices X and Y, first set the screw head 4
The dowel 42, the check ring 70, and the tubular portion 42't of the dowel 42 'are inserted into the 0 "shaft portion in this order, and then the components of the backflow prevention device X are inserted in the above-described order. do it,
When the male screw 44 of the screw head 40 ″ is screwed into the female screw 6 of the screw 1, the backflow preventing devices X and Y are assembled.

The backflow prevention device Y has various effects as described in the section of the prior art, but the first and second check rings 30 and 30 'do not move together with the rotation of the screw 1 during plasticization. Since it is of a rotating type, as described with reference to FIG. 6 (c), between the outer peripheral surfaces of the first and second check rings 30 and 30 ′ and the inner peripheral surface of the heating cylinder 3. It is unavoidable that some molten resin flows back through the gap. On the other hand, the non-circulating check ring can suppress the backflow to some extent. Therefore, according to the fourth embodiment, backflow can be prevented more completely.

This embodiment can also be modified. For example, it is apparent that the backflow prevention device of the first or second embodiment can be applied instead of the backflow prevention device of the third embodiment. In addition, a conventionally known backflow prevention device Y is
It can also be provided on the screw side. It is obvious that the same effect can be obtained even by carrying out in this way.

In the first embodiment, when the front valve seat 10b of the check ring 10 is seated on the seat seat 42b of the stopper plate 42, it is closed tightly, but there is some clearance. Can also be implemented. With this configuration, the pressure of the molten resin on the screw 1 side is higher than the force acting in the direction of separating the front valve seat 10b from the seat seat 42b when the screw 1 is rotationally driven in the plasticizing direction. As a result, even if the front valve seat 10b is pressed against the seat seat 42b, the flow of the molten resin from the screw 1 side to the reservoir 4 side is secured to some extent by the gap.
When the flow of the resin is secured, the pressure of the molten resin on the screw 1 side and that on the reservoir 4 side are balanced, and when the screw 1 is continuously driven in the plasticizing direction, the front valve seat of the check ring 10 is 10b is the seat 42b of the coin 42
Away from. This ensures a complete resin passage.

Further, instead of the clearance, as shown in FIG. 4 (b), the front valve seat 10b of the check ring 10 is replaced.
It is also possible to provide a plurality of notch grooves 80, 80, ... in the circumferential direction. Elements that are the same as the main constituent elements of the embodiment shown in FIG. 1 are given the same reference numerals and are not described in duplicate, but according to the present embodiment, the cutout grooves 80, 80,
Has pressure receiving surfaces 81, 81, which face the screw 1 side. Therefore, the pressure of the molten resin on the side of the screw 1 also acts on these pressure receiving surfaces 81, 81, ..., And acts in the direction of separating the check ring 10 from the seat 42b of the metal plate 42. As a result, the pressure of the molten resin on the screw 1 side when plasticizing and that on the reservoir 4 side are balanced,
The non-return ring 10 is driven as shown in FIG. 1 (a) by the rotation of the screw 1 in the plasticizing direction, and a complete resin passage is secured.

The above-mentioned gaps and notch grooves 80, 80, ...
2, in the embodiment shown in FIG. 2, the front seat 20'b of the second check ring 20 'and the seat seat 4 of the dowel 42.
2b, and in the embodiment shown in FIGS. 3 and 4, the first valve seat 30a of the first check ring 30 and the first seal seat 50a of the seal ring 50.
It is also clear that it can be similarly applied during.

[0053]

As described above, according to the first aspect of the present invention, the check ring has the rear valve seat which is seated on the seat seat at the tip of the screw and the front valve seat which is seated on the seat seat at the head part. A valve seat is formed, and a cam hole formed of a plurality of slide followers having different inclinations is formed inside, and the screw head is provided with a cam pawl that cooperates with the cam hole. When the screw is rotationally driven in the forward direction, the cam claws come into contact with a predetermined sliding follow-up portion of the cam hole to drive the check ring in the axial direction, and both valve seats of the check ring are moved to both seat seats. When it is driven to rotate in the opposite direction, it comes into contact with another slip follower and drives the check ring in the axial direction, and one of the valve seats of the check ring is moved to the screw seat. Seat at the tip of the head or the head Since the seat is seated on the seat of the present invention and is in a closed state, the reverse flow of the molten resin can be more completely prevented even after the plasticizing process and before the injection process, and also during the suck back or the injection process. The effect peculiar to is obtained. Further, according to the present invention, since the valve seats are formed on both sides of the check ring, the check valve is rotatably driven by rotating the screw in the opposite direction before the valve seat of the check ring is seated on the seat. According to the present invention, even if there is a difference in the pressure of the molten resin between the chamber in front of the ring, that is, between the reservoir side and the screw side, or if the check ring does not complete the predetermined locking operation even if the screw is rotated in the reverse direction. Since the seal parts are formed at both ends of the non-return phosphorus, the non-return ring is driven to a lower pressure due to the pressure difference of the molten resin, and one of the non-return ring valve seats is seated on the seat. Sit down. As a result, the effect of preventing the reverse flow or movement of the molten resin to the low pressure side can be obtained. Furthermore, since the resin passage through which the molten resin passes is between the valve seat of the check ring and the seat, and between the outer peripheral surface of the check ring and the inner peripheral surface of the heating cylinder, the cross-sectional area of the resin passage is reduced. It can be taken large if necessary. Therefore, the resin burning phenomenon and the surging phenomenon do not occur. Moreover, since the resin passage of the molten resin is relatively large, the structure is simpler.
It is rarely subject to design restrictions for application to a relatively small injection molding machine. The invention according to claim 2 or 3 can obtain substantially the same effect as the above invention,
According to the invention as set forth in claim 2 or 3, the check ring comprises a plurality of check rings, and when the screw is rotationally driven in the opposite direction, both valve seats of the check ring become the seat seats at the tip of the screw. Since the seat is seated on the head portion to be in the closed state, the effect of completely preventing backflow can be obtained.
Further, according to the invention of claim 4, since the cam hole is provided with the lock portion for maintaining the closed state in which the valve seat of the check ring is seated on the seat seat, it is ensured by setting the lock position. The closed state is maintained. Therefore, even if the backward speed of the screw when sucking back is high,
The check ring follows and the closed state is maintained, and the effect that the molten resin does not flow back from the screw side to the reservoir after sucking back is further obtained. According to the invention described in claim 5, in addition to the above effects, the outer peripheral surface of the heating cylinder is relatively closely contacted with the inner peripheral surface of the heating cylinder so as to be movable in the axial direction independently of the rotation of the screw. The check ring is provided, and a resin passage having a predetermined cross-sectional area is formed between the inner peripheral surface of the check ring and the outer peripheral surface of the shaft portion through which the check ring is inserted. In addition, a check valve is further provided at the end of the check ring, and a valve seat for seating on a seat seat formed on a component of the screw head is formed. By optimizing the clearance between the outer peripheral surface of the ring and the inner peripheral surface of the heating cylinder, the working accuracy, and the like, it is possible to prevent the backflow of the molten resin that may flow back in the invention described in claims 1 to 4. According to the invention described in claim 6, between the front valve seat of the check ring and the seat seat of the head portion or the seat seat of the seal ring, even when the front valve seat is seated on the seat seat, some Because there is a gap,
In addition to the above effects, when the screw is rotationally driven in the plasticizing direction, the pressure of the molten resin on the screw side is higher than the pressure on the reservoir side, and the friction resistance between the heating cylinder and the check ring, the cam Due to the frictional resistance between the hole and the cam claw, the front valve seat of the check ring is pressed against the seat seat and a certain amount of molten resin flows to the reservoir side even when the seat is not separated. Since the flow of the resin is secured, the pressure of the molten resin on the screw side and that on the reservoir side are balanced, and the front valve seat of the check ring is separated from the seat seat. As a result, when a complete resin passage is secured, a sewage effect can be obtained. According to the invention described in claim 7, since the front valve seat is formed with a plurality of notched grooves in which the pressure receiving surface on which the molten resin acts faces the screw side, the molten resin on the screw side during plasticization is formed. The pressure is balanced with that on the reservoir side, and the rotation of the screw in the plasticizing direction drives the check ring in the direction in which the front valve seat separates from the seat seat, and the effect of ensuring a complete resin passage is obtained.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view of a main part of a first embodiment of the present invention, in which (a) is a cross-sectional view in which a check ring is in an open state and (b) is in a closed state. It is a certain sectional view.

FIG. 2 is a partial cross-sectional view showing a main part of a second embodiment of the present invention, in which (a) is a cross-sectional view in which a check ring is in an open state and (b) is in a closed state. It is a certain sectional view.

FIG. 3 is a diagram showing a partial cross-section of a main part of a third embodiment of the present invention, in which (a) is a cross-sectional view in which a check ring is in an open state, and (b) is disassembled. Figure, part (c)
FIG. 4 is a sectional view in a closed state.

FIG. 4 is a view showing still another embodiment of the present invention,
(A) is a cross-sectional view showing a fourth part, and (B) is a partial cross-sectional view showing an essential part of the fifth embodiment.

FIG. 5 is a partial cross-sectional view of a conventional example, in which (a) is a rotating type and (b) is a non-circulating type backflow prevention device.

FIG. 6 is a diagram schematically showing the operation of a conventional recirculation type backflow prevention device, in which (a) to (d) are cross-sectional views showing different states.

[Explanation of symbols]

1
Screw 3
Heating cylinder 4
Reservoirs 10, 20, 20 ', 30, 30'
Non-return ring 11, 21, 32, 32 '
Cam holes 18, 25, 60, 60 '
Cam claw 40, 40 '
Screw heads 43, 43a, 43'b
Small diameter parts 10a, 10b, 20a, 20'b, 30a, 30'b
Valve seats 2a, 42b, 50a, 50'b
Seat 80
Notch groove

Claims (7)

[Claims] 1. A screw head attached to the tip of a screw provided inside the heating cylinder so as to be driven in the rotational direction and the axial direction, and a screw head inserted into a small-diameter portion of the screw head. It comprises an annular check ring provided axially movable between the tip of the screw and the head of the screw head, and the inner peripheral surface of the check ring and the small diameter of the screw head. A backflow prevention device having a resin passage having a predetermined cross-sectional area formed between the head and the outer peripheral surface of the head portion, wherein the check ring has a rear valve seat and a head which are seated on a seat seat at the tip of the screw. Is formed with a front valve seat to be seated on a seat seat of the section, and a cam hole formed by a plurality of sliding followers having different inclinations is formed inside, and the screw head cooperates with the cam hole. Cam to When the screw is driven to rotate in the forward direction, the cam claw abuts on a predetermined sliding follow-up portion of the cam hole to drive the check ring in the axial direction, and both valve seats of the check ring are provided. Is separated from both seats and is in an open state, and when it is rotationally driven in the opposite direction, it comes into contact with another slip follower and drives the check ring in the axial direction, and either one of the check rings is pressed. A backflow prevention device in an injection molding machine, wherein a valve seat is seated on a seat seat at a tip portion of the screw or a seat seat at the head portion to be in a closed state. 2. A screw head attached to the tip of a screw provided inside the heating cylinder so as to be driven in the rotational direction and the axial direction, and in a form of being inserted into a small-diameter portion of the screw head. The check ring includes a plurality of annular check rings provided so as to be movable between a tip end portion of a screw and a head portion of the screw head in a direction toward each other and a direction away from each other. A backflow prevention device in which a resin passage having a predetermined cross-sectional area is formed between an inner peripheral surface and an outer peripheral surface of a small diameter portion of the screw head, wherein the check ring includes a seat seat at a tip portion of the screw. A rear valve seat which is seated on the front seat and a front valve seat which is seated on the seat seat of the head portion are formed, and a cam which comprises a plurality of slide followers of different inclinations is formed inside the plurality of check rings. a hole In addition, the screw head is provided with a cam pawl that cooperates with the cam hole, and when the screw is driven to rotate in the forward direction, the cam pawl comes into contact with a predetermined sliding follow-up portion of the cam hole. Drive the check rings toward each other so that both valve seats of the check ring are separated from the seat seats and are in an open state. The non-return rings are driven in directions away from each other so that both valve seats of the non-return ring are seated on the seat seat at the tip portion of the screw and the seat seat of the head portion to be in a closed state. A backflow prevention device for an injection molding machine. 3. A screw head attached to the tip of a screw provided in the heating cylinder so as to be driven in the rotational direction and the axial direction, and a screw head inserted into a small diameter portion of the screw head. A plurality of annular check rings provided so as to be movable between a tip end portion of the screw and a head portion of the screw head in a direction away from each other and a direction approaching each other, and the plurality of check rings. And a seal ring provided in the small diameter portion of the screw head so as to be interposed between the check head and the inner peripheral surface of the check ring and the outer peripheral surface of the small diameter portion of the screw head. A backflow prevention device in which a resin passage is formed, wherein the plurality of check rings include a rear valve seat seated on one seat seat of the seal ring and a front valve seat seated on the other seat seat. Is that And a cam hole composed of a plurality of slide followers is formed in the side portion, and the screw head or the screw is provided with a cam pawl that cooperates with the cam hole. When rotationally driven in the positive direction, the cam claws abut against a predetermined sliding follow-up portion of the cam hole to drive the check rings in a direction in which they are separated from each other, and the valve seats of the plurality of check rings are sealed. When the ring is separated from the seat and opened, and is driven to rotate in the opposite direction, the rings come into contact with other slip followers and drive the plurality of check rings toward each other, and the plurality of check rings are moved. A backflow prevention device in an injection molding machine, wherein a valve seat of the ring is seated on a seat seat of the seal ring to be in a closed state. 4. The injection molding, wherein the cam hole according to any one of claims 1 to 3 is provided with a lock portion for maintaining a closed state in which the valve seat of the check ring is seated on the seat seat. Backflow prevention device in machine. 5. A combination of the backflow prevention device according to any one of claims 1 to 4 and another backflow prevention device, wherein the other backflow prevention device has an outer peripheral surface inside the heating cylinder. It is composed of an annular check ring that is in close contact with the peripheral surface and is movable in the axial direction independently of the rotation of the screw, and the inner peripheral surface of the check ring and the check ring are A resin passage having a predetermined cross-sectional area is formed between the inserted shaft portion and the outer peripheral surface of the shaft portion, and a seat seat formed on a component of the screw head is formed at an end portion of the check ring. A backflow prevention device in an injection molding machine, in which a valve seat to be seated on is formed. 6. The front valve seat is provided between the front valve seat of the check ring according to any one of claims 1 to 5 and the seat seat of the head portion or the seat seat of the seal ring. A backflow prevention device in an injection molding machine, which is configured so that there is a slight gap when it is seated on a seat. 7. The injection molding, wherein the front valve seat according to any one of claims 1 to 5 has a plurality of notched grooves whose pressure receiving surface on which the molten resin acts faces the screw side. Backflow prevention device in machine.