JP2023115453A - Backflow prevention device, screw, and injection molding machine - Google Patents

Abstract

To provide a non-cooperative backflow prevention device that suppresses variation in injection volume.SOLUTION: A backflow prevention device (25) in which a backflow prevention ring (30) rotates relative to a head (32) during metering includes: a push metal (27); a shaft (28) protruding from the push metal; the backflow prevention ring (30) penetrated through the shaft (28); and the head (32) provided at a tip of the shaft (28). The head (32) includes a plurality of contact surfaces (42) that contact an end surface (34) of the backflow prevention ring (30). A ringing release structure (43) is formed near these contact surfaces (42) to release ringing caused by the contact surface (42) and the end surface (34) coming into close contact.SELECTED DRAWING: Figure 3A

Description

The present invention relates to a backflow prevention device provided on a screw of an injection molding machine, a screw provided with the backflow prevention device, and an injection molding machine.

A screw of an injection molding machine is provided with a backflow prevention device at its tip as described in Patent Document 1. The backflow prevention device is composed of a presser metal provided at the tip of the screw, a screw head similarly provided at the tip of the screw, and a backflow prevention ring. The screw head is composed of a tip portion and a small-diameter shaft portion, and the shaft portion is connected to the end portion of the screw. A backflow prevention ring is passed through the shaft and is slidable between the head and the presser metal.

A gap through which the injection material flows is formed between the backflow prevention ring and the shaft portion, and a groove through which the injection material flows is formed in the outer peripheral surface of the head portion. Therefore, when the screw is rotated to feed the melted injection material forward, the anti-backflow ring is pushed forward by the injection material and a part of its end surface comes into contact with the rear end surface of the head portion, that is, the contact surface. The injection material is sent forward through the gap between the anti-backflow ring and the shaft and the groove in the head. i.e. weighed. On the other hand, when the screw is driven forward, the pressure of the injection material acts on the end face of the anti-backflow ring. The opposite end face of the anti-reflux ring is pressed against the pusher to close the flow path of the injected material. This prevents the backflow of the injection material and allows the injection material to be injected into the mold.

There are two types of backflow prevention devices: a so-called co-rotating type in which the backflow prevention ring rotates together with the screw when the screw is rotated for metering, and a so-called non-co-rotating type in which the backflow prevention ring does not rotate together with the screw. . In the non-corotating type, the anti-backflow ring slides and rotates while its end surface is in contact with the contact surface of the head portion of the screw head during metering. Therefore, the contact surface of the head portion is processed into a smooth surface in order to prevent the end surface of the backflow prevention ring from being worn due to sliding.

JP-A-2003-62879

In the non-corotating backflow prevention device, the contact surface of the head portion of the screw head is formed to be a smooth surface, so that the backflow prevention ring can be prevented from wearing. However, the injection amount may not be stable. That is, the screw position at the completion of injection and holding pressure may vary for each molding cycle.

The present disclosure provides a non-corotating backflow prevention device capable of suppressing variations in the injection amount, a screw equipped with such a backflow prevention device, and an injection molding machine.

Other problems and novel features will become apparent from the description of the specification and the accompanying drawings.

The present disclosure includes a pusher, a shaft protruding from the pusher, a backflow prevention ring penetrated by the shaft, and a head provided at the tip of the shaft, wherein the backflow prevention ring is The object is a backflow prevention device that rotates relative to the head during weighing. The head portion has a plurality of contact surfaces that contact the end surface of the anti-backflow ring. A ringing canceling structure is formed in the vicinity of one or more contact surfaces of such a plurality of contact surfaces for canceling ringing in which the contact surface and the end surface are brought into close contact with each other.

The present disclosure can suppress variations in the injection amount.

1 is a front view showing an injection molding machine according to an embodiment; FIG. 1 is a front cross-sectional view showing a part of a backflow prevention device and an injection device according to the present embodiment; FIG. FIG. 3 is a front cross-sectional view showing an enlarged part of the backflow prevention device according to the present embodiment indicated by symbol X in FIG. 2; FIG. 3 is a front cross-sectional view showing an enlarged part of the backflow prevention device according to the present embodiment indicated by symbol X in FIG. 2; FIG. 3 is a side cross-sectional view of the backflow prevention device according to the present embodiment shown in the YY cross section in FIG. 2; FIG. 5 is a front cross-sectional view showing an enlarged part of a backflow prevention device according to a second embodiment; FIG. 11 is a front cross-sectional view showing an enlarged part of a backflow prevention device according to a third embodiment; FIG. 11 is a side cross-sectional view showing an enlarged part of a backflow prevention device according to a fourth embodiment; FIG. 11 is a side cross-sectional view showing an enlarged part of a backflow prevention device according to a fifth embodiment; It is a figure for demonstrating an experimental method, and is front sectional drawing which shows a screw head and a backflow prevention ring. It is a photograph of a screw head and a backflow prevention ring which shows an experimental result.

Specific embodiments will be described in detail below with reference to the drawings. However, it is not limited to the following embodiments. For clarity of explanation, the following description and drawings have been simplified where appropriate. In each drawing, the same elements are denoted by the same reference numerals, and redundant description is omitted as necessary. In addition, there are portions where hatching is omitted so as not to complicate the drawing.

This embodiment will be described.
<Injection molding machine>
An injection molding machine 1 according to the present embodiment includes a toggle-type mold clamping device 2 and an injection device 3, as shown in FIG.

<Mold clamping device>
The mold clamping device 2 includes a fixed platen 5 fixed to the bed B, a movable platen 7 slidably provided on the bed B, and a mold clamping housing 6 . The fixed platen 5 and the mold clamping housing 6 are connected by a plurality of tie bars 9, 9, . . . A mold clamping mechanism 11 is provided between the mold clamping housing 6 and the movable platen 7 . In this embodiment, the mold clamping mechanism 11 consists of a toggle mechanism 11 . The stationary platen 5 and the movable platen 7 are provided with a fixed side mold 13 and a movable side mold 14, respectively. Therefore, when the toggle mechanism 11 is driven, the molds 13 and 14 are opened and closed.

<Injection device>
The injection device 3 includes a heating cylinder 16 , a screw 17 provided inside the heating cylinder 16 , and a screw driving device 18 . The heating cylinder 16 is supported by a screw driving device 18, and the screw 17 is driven by the screw driving device 18 in the rotational direction and the axial direction. A hopper 20 and an injection nozzle 22 are provided in the heating cylinder 16 . When the injection material is supplied from the hopper 20, the heating cylinder 16 is heated, and the screw 17 is rotated by the screw driving device 18, the injection material is melted and weighed. The injection material can be injected into the molds 13 and 14 by driving the screw 17 in the axial direction by the screw driving device 18 .

<Backflow prevention device according to the present embodiment>
A backflow prevention device 25 according to the present embodiment is provided at the tip of the screw 17, as shown in FIG. The backflow prevention device 25 includes a pusher 27 provided at the tip of the screw 17 , a small-diameter shaft portion 28 projecting forward from the pusher 27 , and a backflow prevention ring 30 inserted into the shaft portion 28 . , and a head portion 32 provided at the tip of the shaft portion 28 .

The anti-backflow ring 30 has an outer peripheral surface that slides against the bore of the heating cylinder 16 with a slight clearance, so that the injection material does not leak from this portion. The inner diameter of the backflow prevention ring 30 is sufficiently larger than the outer diameter of the shaft portion 28, and the gap between the shaft portion 28 and the backflow prevention ring 30 serves as a flow path for the injection material to flow. The anti-backflow ring 30 is formed with an end face 34 on the head portion 32 side and a closed end face 35 on the pusher 27 side. When the anti-reflux ring 30 seats against the pusher 27, the closed end face 35 contacts the pusher 27 to close the flow path of the injected material. That is, backflow of the injection material is prevented.

The head portion 32 has a plurality of grooves 37, 37, . FIG. 3C shows a side view of the head portion 32. In this embodiment, the number of the grooves 37, 37, . . . It's becoming . . are provided with reinforcing tips 40, 40, . . . The reinforcing tips 40, 40, .

Each of the reinforcing tips 40, 40, . . . has two faces, as shown in FIG. 3A. That is, a contact surface 42 that contacts the end surface 34 of the backflow prevention ring 30 and an inclined surface 43 that is in contact with the contact surface 42 and formed at an angle θ different from that of the contact surface 42 . When the screw 17 (see FIG. 2) is rotated to meter the injection material, the anti-reflux ring 30 contacts and slides against the contact surface 42 with its end surface 34 as shown in FIG. 3B. They rotate relative to each other while moving. That is, the backflow prevention device 25 according to the present embodiment is of a non-corotating type. Therefore, the contact surface 42 is a smooth surface so that the end surface 34 of the anti-backflow ring 30 is not worn.

By the way, in such a non-corotating type backflow prevention device 25, a phenomenon may occur in which the injection amount is not stabilized at the time of injection. In other words, the backflow preventive device 25 may not function properly, causing a backflow of the injection material. The inventors have found that this phenomenon is caused by so-called ringing, in which the contact surface 42 of the head portion 32 and the end surface 34 of the anti-backflow ring 30 are in close contact with each other. In other words, it has been found that the smooth surface of the contact surface 42 causes a strong contact with the end surface 34, which may delay the timing of separation of the anti-backflow ring 30 from the head portion 32 during injection. .

Therefore, the inventors formed the inclined surface 43 adjacent to the contact surface 42 in the head portion 32 . FIG. 3B shows a state in which the end surface 34 of the anti-backflow ring 30 is in close contact with the contact surface 42 of the head portion 32 . At this time, a wedge-shaped gap is formed between the inclined surface 43 and the end surface 34 . When the injection material enters this gap, the pressure of the injection material increases in the gap, and the ringing is easily released. That is, in the present embodiment, the inclined surface 43 has a ringing cancellation structure. As a result, there is no delay in the timing at which the anti-backflow ring 30 separates from the head portion 32 during ejection. In other words, the injection amount is stable. In this embodiment, the ringing canceling structures or inclined surfaces 43, 43, . . .

By the way, in the present embodiment, as shown in FIG. 2, the head portion 32 and the shaft portion 28 are formed from a screw head 45 which is one integrally formed component. A male thread 46 is formed on the screw head 45 continuously from the shaft portion 28 . A female screw 48 is formed in the screw 17 , and a screw head 45 is attached to the screw 17 by screwing a male screw 46 into the female screw 48 . It should be noted that the head portion 32 and the shaft portion 28 do not need to be formed from one component, and for example, the shaft portion 28 and the pressing metal 27 may be integrally formed to form one component. In this case, the head portion 32 is fixed to the shaft portion 28 by fixing means such as screws.

<Backflow prevention device according to the second embodiment>
Various modifications of the backflow prevention device 25 according to the present embodiment are possible. FIG. 4 shows a backflow prevention device 25A according to a modified second embodiment. In the second embodiment, the end face 34A of the backflow prevention ring 30A is tapered. A contact surface 42A formed on the reinforcing tip 40 of the head portion 32 is also tapered at the same angle. In this embodiment, the inclined surface 43A, which is the ringing cancellation structure, is a tapered surface that is different from the contact surface 42A by an angle θ'. Also in the backflow prevention device 25A according to the second embodiment, when the end surface 34A of the backflow prevention ring 30A and the contact surface 42A of the head portion 32 are in contact with each other, a wedge-shaped gap is formed between the end surface 34A and the inclined surface 43A. is formed. Therefore, the ringing of the end surface 34A and the contact surface 42A is easily released.

<Backflow prevention device according to the third embodiment>
FIG. 5 shows a backflow prevention device 25B according to a third embodiment. A backflow prevention device 25B according to the third embodiment differs from the first and second embodiments in the ringing canceling structure formed adjacent to the contact surface 42 . In this embodiment, the ringing canceling structure is a stepped portion 50 . The stepped portion 50 is a shallow portion of the contact surface 42 . In the backflow prevention device 25B according to the third embodiment, a gap is formed between the end surface 34 and the stepped portion 50 when the end surface 34 of the backflow prevention ring 30 and the contact surface 42 of the head portion 32 contact each other. . The injected material enters this gap and the pressure increases, so that the ringing between the end surface 34 and the contact surface 42 is easily released.

<Backflow prevention device according to the fourth embodiment>
FIG. 6 shows a backflow prevention device 25C according to a fourth embodiment. In this embodiment, the ringing relief structure consists of shallow grooves 51, 51, . . . formed in the contact surfaces 42, 42, . In the backflow prevention device 25C according to the fourth embodiment, a gap is formed between the end surface 34 and the groove 51 when the end surface 34 of the backflow prevention ring 30 and the contact surface 42 of the head portion 32 contact each other. The injected material enters this gap and the pressure increases, so that the ringing between the end surface 34 and the contact surface 42 is easily released.

<Backflow prevention device according to the fifth embodiment>
FIG. 7 shows a backflow prevention device 25D according to a fifth embodiment. In this embodiment, the ringing release structure is formed only on some of the contact surfaces 42,42. In other words, although there are four contact surfaces 42, 42, . The ringing cancellation structure consists of inclined surfaces 43D, 43D, . . . The positions where the inclined surfaces 43D, 43D, . . . are formed are different from those in the first embodiment. In other words, inclined surfaces 43D, 43D are formed on both sides of the contact surfaces 42, 42, respectively. Also in this fifth embodiment, the ringing is easily released by the action of these inclined surfaces 43D, 43D, . . .

<Other Modifications>
Other modifications of this embodiment or the second to fifth embodiments are possible. For example, although the head portion 32 is provided with the reinforcing tip 40, the reinforcing tip 40 is not essential. If the reinforcing tip 40 is not provided, the contact surface 42, the inclined surface 43, etc. may be formed directly on the head portion 32. FIG. Further, although the number of the blade portions 38, 38 of the head portion 32 is described as being four, the number may be two, three, or five or more.

An experiment was conducted to confirm that ringing between the end face 34 of the backflow prevention ring 30 and the contact surface 42 of the head portion 32 is less likely to occur with the backflow prevention device 25 (see FIG. 3A) according to the present embodiment. If the ringing is properly released, the anti-backflow ring 30 is quickly separated from the head portion 32 and seated on the pusher 27 at the time of injection, preventing the backflow of the injection material and stabilizing the injection amount. It is from. Explain the contents of the experiment.

Experiment content:
As shown in FIG. 8, two screw heads 45z, 45 (see FIGS. 2 and 3A) and two anti-backflow rings 30, 30 were prepared. The left screw head 45z does not form the inclined surface 43 in the head portion 32 . That is, only the contact surface 42 is formed, which is different from the backflow prevention device 25 according to this embodiment. Hereinafter, this will be referred to as Comparative Example Z. On the other hand, the right screw head 45 forms an inclined surface 43 adjacent to the contact surface 42 in the head portion 32 . That is, it is the screw head 45 of the backflow prevention device 25 according to the present embodiment. This will be referred to as Example A hereinafter.

The respective screw heads 45', 45 of Comparative Example Z and Example A were erected on the floor surface. The end surfaces 34, 34 of the backflow prevention rings 30, 30 were coated with Komyotan, respectively, and the backflow prevention rings 30, 30 were lifted and pressed against the head portions 32, 32. When the hand was slowly released from the backflow prevention rings 30, 30, the backflow prevention ring 30 did not drop in the left screw head 45' as shown in FIG. Ring 30 has fallen.

From this experiment, it was found that the backflow prevention ring 30 can be easily separated from the head portion 32 in the backflow prevention device 25 according to the present embodiment in which the ringing canceling structure, that is, the inclined surface 43 is formed adjacent to the contact surface 42 . It could be confirmed. That is, it was confirmed that ringing hardly occurs.

Injection molding was actually performed using the screw 17 (see FIG. 2) to which the backflow prevention device 25 of Example A was attached and the screw 17 to which the backflow prevention device 25 of Comparative Example Z was attached. An experiment was conducted to confirm whether or not this occurs.

Experiment content:
The injection process of injecting the injection material into the molds 13 and 14 (see FIG. 1) 30 times using the screws 17 and 17 having the backflow prevention devices 25 and 25 of Example A and Comparative Example Z, respectively. carried out. The screw position of the screw 17 at the completion of each injection process, that is, the amount of cushioning was detected, and the variation thereof was investigated.

Experimental result:
In the screw 17 provided with the backflow prevention device 25 of Example A, the maximum value of the cushion amount is 3.56 mm, the minimum value is 3.48 mm, and the magnitude of 3σ, which is three times the standard deviation, is 0.56 mm. 069 mm.
On the other hand, in the screw 17 provided with the backflow prevention device 25 of Comparative Example Z, the maximum value of the cushion amount was 3.39 mm, the minimum value was 1.56 mm, and the magnitude of 3σ was 1.595 mm.

The variation in the amount of cushion indicates the frequency of occurrence of backflow of the injection material in the backflow prevention device 25 . In other words, if the amount of cushioning is constant, backflow does not occur, and if the amount of cushioning varies, backflow occurs. From the results of the experiment, it was found that the variations in the amount of cushioning were smaller in Example A than in Comparative Example Z. In other words, it was confirmed that the reverse flow of the injection material is less likely to occur in the backflow prevention device 25 according to the present embodiment, which includes the inclined surface 43 of the ringing canceling structure in the head portion 32 . This ensures that the shot volume is stable.

The invention made by the present inventor has been specifically described above based on the embodiments, but the present invention is not limited to the embodiments already described, and various modifications can be made without departing from the scope of the invention. It goes without saying that this is possible. A plurality of examples described above can also be implemented in combination as appropriate.

1 Injection molding machine 2 Mold clamping device 3 Injection device 5 Fixed platen 7 Movable platen 6 Mold clamping housing 9 Tie bar 11 Mold clamping mechanism 13 Fixed side mold 14 Movable side mold 16 Heating cylinder 17 Screw 18 Screw driving device 20 Hopper 22 Injection Nozzle 25 Backflow prevention device 27 Presser 28 Shaft 30 Backflow prevention ring 32 Head 34 End surface 35 Closed end surface 37 Groove 38 Blade 40 Reinforcement tip 42 Contact surface 43 Inclined surface 45 Screw head 46 Male screw 48 Female screw 50 Stepped portion 51 groove

Claims (18)

a pusher provided at the tip of the screw of the injection device;
a shaft provided to protrude from the pusher;
a backflow prevention ring penetrated by the shaft;
a head portion provided at the tip of the shaft portion,
The anti-backflow ring rotates relative to the head portion during weighing,
The head portion has a plurality of contact surfaces that come into contact with the end surfaces of the backflow prevention ring, and one or more of the contact surfaces are located in the vicinity of the contact surfaces in order to cancel ringing in which the contact surfaces and the end surfaces are in close contact with each other. A backflow prevention device in which a ringing cancellation structure is formed. 2. The backflow prevention device according to claim 1, wherein said plurality of contact surfaces are smooth surfaces. 3. The backflow prevention device according to claim 1, wherein said head portion and said shaft portion are integrally formed as a screw head. The head portion has a plurality of blade portions formed by a plurality of grooves formed on the outer peripheral surface thereof,
The backflow prevention device according to any one of claims 1 to 3, wherein the contact surface is formed at an end portion of the blade portion on the presser metal side. A reinforcing tip made of a metal material harder than the metal material forming the head portion is provided at the end portion of the plurality of blade portions on the presser metal side,
5. The backflow prevention device according to claim 4, wherein said contact surface is formed on said reinforcing tip. The backflow prevention device according to any one of claims 1 to 5, wherein said ringing canceling structure is formed in the vicinity of all of said plurality of contact surfaces. The ringing canceling structure comprises an inclined surface which is continuous with the contact surface and formed at an angle different from that of the contact surface. The backflow prevention device according to any one of claims 1 to 6, wherein a gap of . The ringing canceling structure comprises a stepped portion formed adjacent to the contact surface, and a gap is formed between the stepped portion and the end surface when the contact surface and the end surface are brought into close contact with each other. The backflow prevention device according to any one of claims 1 to 6, wherein The backflow prevention device according to any one of claims 1 to 6, wherein said ringing canceling structure comprises a groove formed in said contact surface so as to traverse said contact surface. A screw that is inserted into a heating cylinder of an injection device,
The screw includes a screw body,
and a backflow prevention device,
The backflow prevention device includes a presser metal provided at the tip of the screw body,
a shaft provided to protrude from the pusher;
a backflow prevention ring penetrated by the shaft;
a head portion provided at the tip of the shaft portion,
The anti-backflow ring rotates relative to the head portion during weighing,
The head portion has a plurality of contact surfaces that come into contact with the end surfaces of the backflow prevention ring, and one or more of the contact surfaces are located in the vicinity of the contact surfaces in order to cancel ringing in which the contact surfaces and the end surfaces are in close contact with each other. A ringing release structure is formed on the screw. 11. The screw according to claim 10, wherein said multi-sided contact surfaces are smooth surfaces. The head portion and the shaft portion are integrally formed as a screw head,
The head portion has a plurality of blade portions formed by a plurality of grooves formed on the outer peripheral surface thereof,
12. The screw according to claim 10, wherein the contact surface is formed at the end of the blade portion on the presser metal side. A reinforcing tip made of a metal material harder than the metal material forming the head portion is provided at the end portion of the plurality of blade portions on the presser metal side,
13. The screw of claim 12, wherein said contact surface is formed on said reinforcing tip. 14. The screw according to any one of claims 10 to 13, wherein said ringing canceling structure is formed in the vicinity of all of said plurality of contact surfaces. The ringing canceling structure comprises an inclined surface which is continuous with the contact surface and formed at an angle different from that of the contact surface. 15. The screw according to any one of claims 10 to 14, which is adapted to form a gap of . The ringing canceling structure comprises a stepped portion formed adjacent to the contact surface, and a gap is formed between the stepped portion and the end surface when the contact surface and the end surface are brought into close contact with each other. The screw according to any one of claims 10 to 14, wherein the screw is The screw according to any one of claims 10 to 14, wherein said ringing release structure comprises a groove formed in said contact surface across said contact surface. an injection device for injecting an injection material;
An injection molding machine comprising a mold clamping device that clamps a mold,
The injection device includes a heating cylinder,
a screw contained within the heating cylinder;
The screw includes a screw body,
and a backflow prevention device,
The backflow prevention device includes a presser metal provided at the tip of the screw body,
a shaft provided to protrude from the pusher;
a backflow prevention ring penetrated by the shaft;
a head portion provided at the tip of the shaft portion,
The anti-backflow ring rotates relative to the head portion during weighing,
The head portion has a plurality of contact surfaces that come into contact with the end surfaces of the backflow prevention ring, and one or more of the contact surfaces are located in the vicinity of the contact surfaces in order to cancel ringing in which the contact surfaces and the end surfaces are in close contact with each other. An injection molding machine in which a ringing release structure is formed.

Images