JPH11291306A - Back flow preventing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance durability. SOLUTION: A head main body part 61, a screw head 14 having a small diameter part 62, the non-return ring 51 arranged to the periphery of the small diameter part 62 in a relatively freely rotatable manner with respect to the screw head 14 and the seal ring 52 arranged behind the small diameter part 62 so as to be freely separable from the non-return ring 51 are provided. An annular first antiwear means is arranged to one of the rear end surface of the head main body part 61 and the front end surface of the non-return ring 51 and a plurality of second antiwear means having hardness higher than that of the first antiwear means are embedded in the other one of them and a resin flow channel is formed between the second antiwear means. The pressure of the resin is absorbed by the peripheral parts of the second antiwear means.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backflow prevention device.

[0002]

2. Description of the Related Art Conventionally, an injection molding machine has an injection device, and a screw is disposed in a heating cylinder of the injection device so as to be rotatable and advanceable and retractable. The screw is rotated by driving a driving means. Or move forward and backward. And during the weighing process,
When the screw is rotated by driving the driving means, the resin dropped from the hopper is melted and stored in front of the screw head, and at this time, the screw is retracted by the pressure of the resin. Also,
When the screw is advanced without rotating by driving the driving means during the injection step, the resin stored in front of the screw head is injected from the injection nozzle.

By the way, a backflow prevention device is provided to prevent the resin stored in front of the screw head from flowing backward during the injection step. That is, an annular check ring is provided on the outer periphery of the small diameter portion of the screw head, and a seal ring is provided at the front end of the screw so as to be able to freely contact and separate from the rear end of the check ring. Therefore, when the screw is advanced during the injection step, the resin stored in front of the screw head flows backward and tends to move backward, but the check ring is relatively moved with respect to the screw by the pressure of the resin. Since it moves backward and seals by contacting the seal ring, it is possible to prevent the resin stored in front of the screw head from flowing backward.

However, in a counter-rotating type backflow prevention device in which the check ring is rotated as the screw rotates, the inner peripheral surface of the heating cylinder and the outer peripheral surface of the check ring slide. As a result, the durability of the check ring is reduced, and the check ring is galled. Therefore, there has been provided a non-co-rotating type backflow prevention device in which the check ring does not rotate even when the screw rotates.

[0005] In this case, the inner peripheral surface of the heating cylinder and the outer peripheral surface of the check ring do not slide, but the screw head and the check ring slide during the weighing process, and the screw head and the check ring do not slide. The ring will be worn. Especially,
When performing injection molding using a resin that is extremely difficult to form a resin film on the sliding surface, such as a special resin or a resin containing silicone as an additive, the amount of wear on the screw head and check ring is reduced. Will increase.

Therefore, a backflow prevention device having improved durability has been provided. FIG. 2 is a diagram showing a first example of a conventional backflow prevention device. In the figure, 11 is a heating cylinder, 1
2 is a screw, 14 is a screw head, 18 is a metering part, 20 is a check ring made of a super-hard alloy, 22 is a seal ring, and 35 is formed at the rear end of the screw head 14 (right end in FIG. 2). The male screw 36 is a female screw formed at the front end (left end in FIG. 2) of the screw 12.

Reference numeral 31 denotes a ceramic ring provided on the surface of the screw head 14 facing the seal ring 22. In this case, since the ring 31 is brittle (fragile) and easily broken,
Project forward in the form of a sleeve, and screw head 14
Is screwed into the screw 12 so as to sandwich the ring 31.

FIG. 3 is a diagram showing a second example of a conventional backflow prevention device. In the figure, 11 is a heating cylinder, 12 is a screw, 14 is a screw head, 32 is a check ring, and 34 is a seal ring. Reference numeral 33 denotes a ceramic liner disposed on the surface of the check ring 32 facing the screw head 14.

[0009]

However, in the above-described conventional backflow prevention device, the pressure of the resin stored in front of the screw head 14 during the injection step is reduced by the ring 31.
(FIG. 2) and the liner 33. At this time, the processing accuracy of the mating surface of the ring 31 with the screw head 14 and the seal ring 22 and the processing accuracy of the mating surface of the check ring 32 with the liner 33 are low. , Ring 31 and liner 3
3, a bending stress occurs locally as well as a compressive stress, and the ring 31 and the liner 33 are broken. as a result,
The durability of the backflow prevention device is reduced.

In particular, in the case of the backflow prevention device shown in FIG. 2, when the screw head 14 is screwed into the screw 12, if the tightening torque is not sufficiently controlled, an excessive tightening force is applied to the ring 31. Therefore, the ring 31 is more easily broken. SUMMARY OF THE INVENTION It is an object of the present invention to provide a backflow prevention device capable of solving the problems of the conventional backflow prevention device and improving durability.

[0011]

For this purpose, a backflow prevention device according to the present invention comprises a screw head having a head main body and a small diameter portion, and a rotatable relative to the screw head around the small diameter portion. And a seal ring disposed at the rear of the small diameter portion so as to be able to freely contact and separate from the check ring.

An annular first wear-resistant means is disposed on one of a rear end face of the head main body and a front end face of the check ring, and the other is provided with a plurality of pieces having higher hardness than the first wear-resistant means. Second anti-wear means is embedded and
A resin flow path is formed between the abrasion-resistant means. In another backflow prevention device according to the present invention, the first wear-resistant means is disposed on a rear end face of the head body, and the second wear-resistant means is embedded in a front end face of the check ring. Is done.

In still another backflow prevention device according to the present invention, the first wear-resistant means is made of a super-hard alloy, and the second wear-resistant means is made of ceramic. In still another backflow prevention device of the present invention, the outer diameter of the first wear-resistant means is made smaller than the outer diameter of the second wear-resistant means.

In still another backflow prevention device according to the present invention, the outer diameter of the first wear-resistant means is made larger as it approaches the second wear-resistant means.

[0015]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a sectional view of a backflow prevention device according to a first embodiment of the present invention.
FIG. 2 is a front view of the check ring according to the first embodiment of the present invention. In the drawing, reference numeral 11 denotes a heating cylinder, and the heating cylinder 11 has an injection nozzle (not shown) at a front end (left end in FIG. 1). A screw 12 is rotatably and reciprocally disposed within the heating cylinder 11 so that the screw 12 can be rotated or moved forward and backward by driving a driving unit (not shown). .

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

In the measuring step, when the screw 12 is rotated by driving the driving means, the pellet-shaped resin dropped from a hopper (not shown) enters the heating cylinder 11 and flows through the groove 16. It is advanced (moved to the left in FIG. 2), melted by a heater (not shown), and stored in front of the screw head 14 (to the left in FIG. 2). At this time, the screw 12 is moved backward (moves rightward in FIG. 1) by receiving the pressure of the resin.

When the screw 12 is advanced without rotating by driving the driving means during the injection step, the resin stored in front of the screw head 14 is injected from the injection nozzle, and a mold (not shown) is used. Is filled in the cavity space. by the way,
A backflow prevention device is provided to prevent the resin stored in front of the screw head 14 from flowing backward during the injection process. The backflow prevention device includes a screw head 14, a check ring 51 made of a steel-based material, and a seal ring 52. The screw head 14 has a conical (conical) head body at a front portion (left portion in FIG. 1). A portion 61 has a small-diameter portion 62 at the center, and a screw portion 63 at the rear (the right portion in FIG. 1). On the other hand, a screw hole 64 is formed in the front part of the metering part 18 so as to correspond to the screw part 63. Then, a male screw 65 formed on the outer peripheral surface of the screw portion 63 and a female screw 66 formed on the inner peripheral surface of the screw hole 64 are screwed together, and the screw head 14 is screwed into the metering portion 18. I have.

An annular check ring 51 is provided on the outer periphery of the small diameter portion 62, and a resin flow path 71 is formed between the small diameter portion 62 and the check ring 51. A seal ring 52 is provided at the front end of the metering portion 18 so as to be able to freely contact and separate from the rear end of the check ring 51. The non-return ring 51 has a non-corotating structure so as not to rotate in conjunction with the rotation of the screw 12.

Therefore, when the screw 12 is advanced during the injection step, the resin stored in front of the screw head 14 flows backward and moves backward, but the check ring 51 is moved by the pressure of the resin. The check ring 5 moves relatively rearward with respect to the screw 12.
Since the rear end of the screw head abuts against the seal ring 52 to perform sealing, it is possible to prevent the resin stored in front of the screw head from flowing backward.

In the non-co-rotating type backflow prevention device of this type, when the screw 12 is rotated backward during the measuring step, the check ring 51 is moved relative to the screw 12 by the pressure of the resin. To the screw head 14 and the check ring 51
Is slid. Therefore, a ring 72 made of a super-hard alloy as an annular first wear-resistant means is disposed on the surface of the screw head 14 facing the check ring 51, that is, on the rear end surface of the head body 61. In this case, the ring 72 is mechanically fixed to the screw head 14 by a screw (not shown) or the like. In addition, it can be fixed by a method as shown in FIG.

On the other hand, the surface of the check ring 51 facing the screw head 14, that is, the check ring 51
A plurality of (six in the present embodiment) fan-shaped convex portions 74 are formed at a predetermined pitch on the front end surface of each of the convex portions 7.
A ceramic, fan-shaped sliding member 73 as a second wear-resistant means is disposed in the front end 4 with its front end exposed. For this purpose, a groove 74a is formed in each of the projections 74, and each of the sliding members 73 is embedded in the groove 74a.
A resin flow path 78 is formed between the convex portions 74 in the circumferential direction.

In this case, the toughness of the ring 72 is made higher than that of the sliding member 73, and the hardness of the sliding member 73 is made higher than the hardness of the ring 72. The sliding member 73
Is fixed to the convex portion 74 by a fixing method such as brazing, an inorganic adhesive, shrink fitting, etc. The fixing method is selected in consideration of the corrosiveness of the resin used for injection molding. Is done. After the sliding member 73 is buried in the groove 74a, the front end face of the check ring 51 is ground by a surface grinder (not shown) or the like, so that the flatness is obtained.

As described above, by disposing the ring 72 on the rear end face of the head body 61 and disposing the sliding member 73 on the front end face of the check ring 51, the screw head 14
In addition, the durability of the check ring 51 can be improved. Further, even if the pressure of the resin stored in front of the screw head 14 is applied to the screw head 14 during the injection step, each sliding member 73 is buried in the groove 74a. Part, that is, convex portion 7
4 allows the pressure to be absorbed. Therefore, the compressive stress generated in the sliding member 73 can be reduced. Further, since each of the sliding members 73 is surrounded by the projection 74, it is possible to prevent the bending stress from being generated in the sliding members 73.

As a result, the breaking of the sliding member 73 can be prevented, so that the durability of the backflow prevention device can be improved. In the measuring step, the check ring 51 and the head main body 61 abut against each other. However, since the sliding member 73 is surrounded by the convex portion 74, it does not directly receive the pressure of the resin in the resin flow path 71. . Therefore, since the compressive stress generated in the sliding member 73 can be reduced, the durability of the backflow prevention device can be improved accordingly.

In the measuring step, the check ring 51 is used.
And the head main body 61 abut against each other.
Is formed, the resin advanced in the groove 16 passes through the resin flow paths 71 and 78 and the screw head 14
Stored in front of Therefore, the movement of the resin is not hindered. In the present embodiment, the head body 6
A ring 72 is disposed on one side and a sliding member 73 is embedded on the check ring 51 side. However, the ring 72 is disposed on the check ring 51 side and the head body 61 side. The sliding member 73 can be embedded.

Next, a second embodiment will be described. In addition, about what has the same structure as 1st Embodiment, the description is abbreviate | omitted by attaching the same code | symbol. FIG. 5 is a sectional view of the backflow prevention device according to the second embodiment of the present invention. In this case, the check ring 15
The front end surface of the first member 1 is flattened, and a sliding member 173 as a ring-shaped second wear-resistant means is embedded in the front end surface so as to expose the front end.

On the other hand, the first end of the head body 161
A ring 172 made of a super-hard alloy is provided as a wear-resistant means, and a resin flow path 81 extending in the axial direction is formed at a plurality of locations in the circumferential direction of the head body 161 and the ring 172. In the present embodiment, the sliding member 1
Since 73 can be used, processing becomes easy,
The cost of the backflow prevention device can be reduced.

Next, a third embodiment will be described. In addition, about what has the same structure as 1st Embodiment, the description is abbreviate | omitted by attaching the same code | symbol. FIG. 6 is a sectional view of a main part of a backflow prevention device according to a third embodiment of the present invention. In this case, a sliding member 73 as a fan-shaped second wear-resistant means is embedded in the front end face of the check ring 51 so as to expose the front end. A ring 272 made of a super-hard alloy is provided on the rear end face of the head main body 61 as first wear-resistant means.

The outer diameter at the rear end of the ring 272 is made smaller than the outer diameter of the sliding member 73 by a predetermined amount δ (about 1 [mm] in the present embodiment). The outer diameter of the ring 272 is increased as it approaches the sliding member 73 side, and the outer peripheral surface is tapered. By the way, since the hardness of the ring 272 is lower than the hardness of the sliding member 73, when the injection molding is repeated, first, the ring 272 mainly wears, and then the sliding member 73 wears. The wear limit of the ring 272 is 2-3 [m
m], and the wear limit of the sliding member 73 is about 0.5 [mm].

In this case, even if the rear end face of the ring 272 is worn by the sliding member 73, the outer diameter at the rear end of the ring 272 is smaller than the outer diameter of the sliding member 73. It becomes flat and no cup-shaped concave surface is formed. Therefore, the resin flow path 78
Not only the flow of the resin in FIG. 4 is not disturbed but also the resin does not stay on the cup-shaped concave surface. When the cup-shaped concave surface is formed deeply, chips are generated at the peripheral portion of the ring 272 due to the flow of the resin, and the fragments are mixed into the resin, or the fragments are clogged on the downstream side in the resin flow direction. Disappears.

When the injection molding is repeated, the front end face of the sliding member 73 is slightly worn by the ring 272 to form a cup-shaped concave surface.
Since the outer peripheral surface of 2 is tapered, the ring 272 wears more than the sliding member 73, and the sliding portion of the sliding member 73 with the ring 272 gradually moves toward the center. Therefore, even if a cup-shaped concave surface is formed on the peripheral portion of the sliding member 73, the ring 272 does not hit and cause chipping.

The present invention is not limited to the above embodiment, but can be variously modified based on the gist of the present invention, and they are not excluded from the scope of the present invention.

[0034]

As described above in detail, according to the present invention, in the backflow prevention device, a screw head having a head main body and a small diameter portion,
A check ring disposed rotatably relative to the screw head; and a seal ring disposed rearward of the small-diameter portion so as to be able to contact and separate from the check ring.

An annular first wear-resistant means is disposed on one of the rear end face of the head main body and the front end face of the check ring, and the other of the plurality of pieces has a higher hardness than the first wear-resistant means. Second anti-wear means is embedded and
A resin flow path is formed between the abrasion-resistant means. In this case, since the second wear-resistant means is buried in the other of the rear end face of the head main body and the front end face of the check ring, the pressure around the second wear-resistant means absorbs the pressure of the resin. You.
Therefore, the compressive stress generated in the second wear-resistant means can be reduced. Further, since each of the second wear-resistant means is surrounded by the surrounding portion, it is possible to prevent the second wear-resistant means from being subjected to bending stress.

As a result, it is possible to prevent the second wear-resistant means from breaking, and to improve the durability of the backflow prevention device. In another backflow prevention device according to the present invention, the outer diameter of the first wear-resistant means is smaller than the outer diameter of the second wear-resistant means. In this case, even if the first wear-resistant means is worn by the second wear-resistant means,
Since the outer diameter at the rear end of the first wear-resistant means is smaller than the outer diameter of the second wear-resistant means, the rear end face of the first wear-resistant means is always flat and a cup-shaped concave surface is formed. There is no.

Therefore, the flow of the resin is not disturbed, and the resin does not stay on the concave surface of the cup. Further, when the cup-shaped concave surface is formed deeply, the flow of the resin causes a chip on the peripheral portion of the first wear-resistant means, and the debris is mixed into the resin, and the debris is generated on the downstream side in the resin flow direction. No clogging.

[0038] In still another backflow prevention device of the present invention, the outer diameter of the first wear-resistant means is increased as it approaches the second wear-resistant means. In this case, the first
Of the second wear-resistant means, the sliding portion of the second wear-resistant means with the first wear-resistant means gradually moves toward the center. Therefore, even if a cup-shaped concave surface is formed on the peripheral portion of the second wear-resistant means, the first wear-resistant means does not hit the chip and does not cause chipping.

[Brief description of the drawings]

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

FIG. 2 is a diagram showing a first example of a conventional backflow prevention device.

FIG. 3 is a diagram showing a second example of a conventional backflow prevention device.

FIG. 4 is a front view of the check ring according to the first embodiment of the present invention.

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

FIG. 6 is a sectional view of a main part of a backflow prevention device according to a third embodiment of the present invention.

[Explanation of symbols]

 14 Screw Head 51, 151 Check Ring 52 Seal Ring 61, 161 Head Body 62 Small Diameter 72, 172, 272 Ring 73, 173 Sliding Member 78 Resin Flow Path

Claims (5)

[Claims] (A) a screw head having a head main body and a small diameter portion; and (b) a check ring disposed around the small diameter portion so as to be rotatable relative to the screw head. (C) behind the small-diameter portion, a check ring is provided so as to be able to contact and separate from the check ring, and (d) one of a rear end surface of the head body and a front end surface of the check ring. Is provided with a plurality of second wear-resistant means having a higher hardness than the first wear-resistant means, and a plurality of second wear-resistant means are embedded between the first wear-resistant means. A backflow prevention device, wherein a resin flow path is formed in the backflow prevention device. 2. The device according to claim 1, wherein the first wear-resistant means is disposed on a rear end face of the head body, and the second wear-resistant means is embedded in a front end face of the check ring. Backflow prevention device. 3. The backflow prevention device according to claim 1, wherein the first wear-resistant means is formed of a super-hard alloy, and the second wear-resistant means is formed of ceramic. 4. The backflow prevention device according to claim 1, wherein the outer diameter of the first wear-resistant means is smaller than the outer diameter of the second wear-resistant means. 5. The backflow prevention device according to claim 1, wherein an outer diameter of the first wear-resistant means increases as approaching the second wear-resistant means.