JP2880676B2 - Backflow prevention device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[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 movable back and forth, and the screw is rotated or moved forward and backward by driving means. Or to be able to. Then, at the time of the measuring step, the screw is retracted while rotating forward, the resin dropped from the hopper is melted and stored in front of the screw head, and at the time of the injection step,
The screw is advanced to inject from the injection nozzle.

FIG. 2 is a sectional view of a main part of a conventional injection device. In the figure, reference numeral 11 denotes a heating cylinder, and the heating cylinder 11 has an injection nozzle 1 at the tip (left side in the figure).
3 A screw 12 is provided in the heating cylinder 11 so as to be rotatable and movable back and forth, and the screw 12 can be rotated and advanced and retracted by a driving means (not shown). Normal,
An injection cylinder, an electric motor, or the like is used as the driving means.

The screw 12 extends rearward (to the right in the drawing) in the heating cylinder 11, is connected to the driving means at a rear end, and has a screw head 14 at a front end. The surface of the metering portion 18 of the screw 12 has a spiral flight 1
5 are formed, and a groove 16 is formed between the flights 15.

[0005] A hopper (not shown) is provided at a predetermined location behind the heating cylinder 11, and pellet-like resin is charged into the hopper. In the injection device having the above-described configuration, at the time of the measuring step, when the driving unit is driven and the screw 12 is retracted while rotating forward, the pellet-shaped resin in the hopper enters the heating cylinder 11,
The groove 16 is advanced.

A heater (not shown) is provided on the outer circumference of the heating cylinder 11 so that the heating cylinder 11 can be heated by the heater to melt the resin in the groove 16. Therefore, when the screw 12 is retracted by a predetermined amount while rotating forward, one shot of the melted resin is stored in front of the screw head 14.

[0007] When the measuring step is completed in this way,
Suckback is performed so that the resin does not drool from the tip of the injection nozzle 13, and the screw 12 is retracted by a small amount without being rotated. Next, in the injection step, when the driving means is driven to advance the screw 12, the resin stored in front of the screw head 14 is injected from the injection nozzle 13 and is filled in a cavity space of a mold (not shown). (Ten) is done.

By the way, a backflow prevention device is provided to prevent the resin stored in front of the screw head 14 from flowing backward during the injection step. To this end, the screw head 14 has a conical (conical) head body 21 at the front and a small diameter portion 19 at the rear. An annular check ring 20 is provided on the outer periphery of the small diameter portion 19, and a resin flow path 24 is formed between the two. A seal ring 22 is provided at the front end of the metering portion 18 of the screw 12 so as to be able to freely contact and separate from the rear end of the check ring 20.

Therefore, when the screw 12 is advanced during the injection step, the resin stored in front of the screw head 14 tends to move backward, but the check ring 20 is pressed against the screw 12 by the pressure of the resin. , And the rear end of the check ring 20 contacts the front end of the metering portion 18 to perform sealing. As a result, it is possible to prevent the resin stored in front of the screw head 14 from moving backward.

On the other hand, when the screw 12 is retracted while rotating forward in the measuring step, the check ring 20 moves forward relative to the screw 12 due to the pressure of the resin, and the front end of the check ring 20 is moved. Although it is in contact with the rear end of the head main body 21, the notch 25 extending in the axial direction is formed at a plurality of locations around the head main body 21,
The movement of the resin is not hindered.

When the suckback is performed, the resin in the metering portion 18 of the screw 12 is moved forward of the screw head 14.

[0012]

However, in the conventional backflow prevention device, the resin of the metering portion 18 of the screw 12 is moved forward of the screw head 14 when suckback is performed. The amount of resin stored in front of the screw head 14 varies.

Further, the sealing is performed by moving the check ring 20 backward by moving the screw 12 forward, so that the kneading and dispersion state of the resin, the viscosity, the temperature, etc., and the time when the injection process is started. The timing of sealing varies depending on the rise of the screw speed, and the amount of resin flowing backward also varies. Therefore, even if the injection stroke of the screw 12 for each shot is accurate, the amount of injected resin varies. In addition, if the amount of resin moved by suckback is small or the timing of sealing is delayed, a short shot occurs in the molded product, while the amount of resin moved by suckback or the timing of sealing is reduced. If it is too early, burrs will be formed on the molded product.

The present invention solves the problems of the above-described conventional backflow prevention device, and provides a backflow prevention device that prevents the resin from moving due to suck-back and does not change the sealing timing. The purpose is to:

[0015]

For this purpose, in the backflow prevention device of the present invention, a metering portion, a screw head screwed to the metering portion, and a space between the metering portion and the screw head are provided. Arranged, first
A first ring having a resin flow path, and a second resin flow path disposed between the metering portion and the screw head so as to be relatively swingable and adjacent to the first ring; It has a second ring and driving means for selectively rotating the screw forward and backward.

When the screw is rotated forward, the first ring is moved between the first ring and the second ring.
A swing restricting means is formed for connecting the resin flow path and the second resin flow path and for disconnecting the first resin flow path and the second resin flow path when the screw is rotated in the reverse direction. In another backflow prevention device of the present invention, both the first ring and the second ring are disposed rotatably with respect to the screw.

In still another backflow prevention device according to the present invention, the first ring is fixed to the metering portion. In still another backflow prevention device according to the present invention, the first ring is further integrated with the metering portion. In still another backflow prevention device of the present invention, further, the driving unit rotates the screw forward during the measuring step, and reversely rotates the screw after completing the measuring step, during which the screw is completed in the measuring step. Hold in position.

[0018]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a sectional view of a main part of an injection device according to a first embodiment of the present invention.
FIG. 4 is a front view of a first ring according to the first embodiment of the present invention, FIG. 4 is a cross-sectional view of the first ring according to the first embodiment of the present invention, and FIG. 5 is a first embodiment of the present invention. FIG. 6 is a cross-sectional view of the second ring according to the first embodiment of the present invention.

In the figure, 11 is a heating cylinder,
The heating cylinder 11 has an injection nozzle 13 at the tip (left side in the figure). A screw 12 is provided in the heating cylinder 11 so as to be rotatable and movable back and forth, and the screw 12 can be rotated and advanced and retracted by a driving means (not shown). Usually, an injection cylinder, an electric motor or the like is used as the driving means.

The screw 12 extends rearward (to the right in the figure) in the heating cylinder 11, is connected to the driving means at a rear end, and has a screw head 14 at a front end. A spiral flight 15 is formed on the surface of the metering portion 18 of the screw 12, and a groove 16 is formed between the flights 15. A hopper (not shown) is provided at a predetermined location behind the heating cylinder 11, and a pellet-shaped resin is charged into the hopper.

In the injection apparatus having the above-mentioned construction, when the screw 12 is moved backward by rotating the screw 12 in the direction of arrow A in the measuring step, the pellet-like resin in the hopper is heated in the heating cylinder 11. , And is advanced in the groove 16. The heating cylinder 11
A heater (not shown) is arranged on the outer periphery of the heater, and the heater can heat the heating cylinder 11 to melt the resin in the groove 16. Therefore, when the screw 12 is retracted by a predetermined amount while rotating forward, one shot of the melted resin is stored in front of the screw head 14.

In this way, when the measuring process is completed,
Suckback is performed so that the resin does not drool from the tip of the injection nozzle 13, and the screw 12 is retracted by a small amount without being rotated. Next, in the injection step, when the driving means is driven to advance the screw 12, the resin stored in front of the screw head 14 is injected from the injection nozzle 13 and is filled in a cavity space of a mold (not shown). Is done.

By the way, a backflow prevention device is provided to prevent the resin stored in front of the screw head 14 from flowing backward during the injection step. For this purpose, the screw head 14 has a conical head body 21 at the front.
Has a small diameter portion 19 at the rear, and the rear end of the small diameter portion 19 is screwed to the metering portion 18. An annular first ring 31 and a second ring 32 are arranged on the outer circumference of the small diameter portion 19 so as to be adjacent to each other and rotatable with respect to the screw 12. Notches 25 extending in the axial direction are formed at a plurality of locations around the head main body 21.

In this case, the thickness of the first ring 31 is w1, the outer diameter is r1, the inner diameter is r2, and the second ring 32 is
When the thickness is w2, the outer diameter is r3, and the inner diameter is r4, w1 = w2 r1 = r3 r2 = r4. Note that w1 ≠ w2 may be satisfied.

The first ring 31 and the second ring 3
The sum of the thickness w1 and the thickness w2 is slightly smaller than the distance between the rear end of the head main body 21 and the front end of the metering portion 18 so that the screw head 2 and the screw head 14 do not rotate together. Although a clearance of about .1 to 0.2 [mm] is formed, the first ring 31 and the second ring 32 do not move in the axial direction due to switching between injection and metering.

Further, the first ring 31 and the second ring 3
The outer diameters r1 and r3 are slightly smaller than the inner diameter of the heating cylinder 11 and the inner diameters r2 and r4 are slightly larger than the outer diameter of the small diameter portion 19 so that the screw head 14 and the screw head 14 do not rotate together. The first ring 31 has, at the center, an opening 35 through which the small-diameter portion 19 penetrates, and peaks formed at a plurality of positions (four in the present embodiment) in the circumferential direction of the outer peripheral edge over an angle θ1. 36, and a valley 37 as a first resin flow path formed between the peaks 36 over an angle θ2. Then, a pin 39 is formed at one end of the surface S1 of the predetermined peak portion 36 facing the second ring 32 so as to protrude.

On the other hand, the second ring 32 has an opening 45 in the center through which the small-diameter portion 19 penetrates, and is provided at a plurality of positions (four positions in the present embodiment) in the circumferential direction of the outer peripheral edge at an angle θ1. The formed mountain portion 46,
And a valley 47 as a second resin flow path formed between the peaks 46 over an angle θ2. An arc-shaped portion for locking the pin 39 on a surface S2 of the predetermined ring 46 facing the first ring 31 corresponding to the peak 36 on which the pin 39 of the first ring 31 is formed. A regulating long groove 49 is formed. In addition, the regulation long groove 49
Has a first regulating end P1 and a second regulating end P2 at both ends, respectively.
Having.

Accordingly, the first ring 31 and the second ring 32 are relatively swingable, and the swing range is regulated by the swing regulating means including the pin 39 and the regulating long groove 49. . Next, the operation of the backflow prevention device having the above configuration will be described. FIG. 7 is a front view showing a state of the first ring and the second ring during the weighing step in the first embodiment of the present invention, FIG. 8 is a sectional view taken along line XX of FIG.
FIG. 10 is a front view showing a state during an injection step of the first ring and the second ring in the first embodiment of the present invention, FIG. 10 is a sectional view taken along the line YY of FIG. 9, and FIG. It is a time chart of the backflow prevention device in an embodiment. The first ring 31 and the second ring 32 mutually face S1 (FIG. 4)
And the surface S2 (FIG. 6), and with the pin 39
(FIG. 1).

When the screw 12 is positively rotated in the direction of arrow A during the measuring step, the first ring 31
The screw 12 is rotated clockwise in FIG. 3 by the frictional force generated between the screw 12 and the flow of the resin generated as the screw 12 rotates. Subsequently, the second ring 32 is also rotated counterclockwise in FIG. 5 by the frictional force generated between the first ring 31 and the flow of the resin generated as the first ring 31 rotates. Can be

In this case, first, the first ring 31 is rotated first, so that a relative rotation occurs between the first ring 31 and the second ring 32, but thereafter, the pin 39 is restricted. When the first ring 31 and the second ring 32 are brought into contact with the first regulating end P1 of the long groove 49, they are integrally rotated clockwise in FIG. At this time, the valley 37 of the first ring 31 and the valley 47 of the second ring 32 are located at the same position in the circumferential direction and communicate with each other. Moves forward through the valleys 37 and 47 and is stored in front of the screw head 14. The head body 2
A plurality of cutouts 25 extending in the axial direction are formed at a plurality of locations around 1, so that the movement of the resin is not hindered.

When the measuring step is completed in this way,
Before the suck-back, the screw 12 is reversely rotated for a time t at a rotation speed N [rpm] in a direction opposite to the arrow A direction. Then, the first ring 31 is rotated counterclockwise in FIG. 3 by the frictional force generated between the first ring 31 and the resin flow generated by the reverse rotation of the screw 12. Subsequently, the second ring 32
5 is rotated clockwise in FIG. 5 by the frictional force generated between the first ring 31 and the flow of the resin generated as the first ring 31 rotates.

In this case, first, the first ring 31 is rotated first, so that a relative rotation occurs between the first ring 31 and the second ring 32, but thereafter, the pin 39 is restricted. When the first ring 31 and the second ring 32 are brought into contact with the second regulating end P2 of the long groove 49, they are integrally rotated counterclockwise in FIG. At this time, the valley portion 37 of the first ring 31 and the valley portion 47 of the second ring 32 are placed at different positions in the circumferential direction, are not communicated, and are sealed.

When the screw 12 is rotated in the reverse direction, the screw 12 tends to advance due to the screw effect. To prevent this, the driving means (not shown) moves the screw 12 to a position where the measuring step is completed. Hold. Therefore, suck-back can always be performed at the measurement process completion position, and the injection process can be started at the measurement process completion position, thereby preventing a variation in the amount of resin injected for each shot. Can be.

Thereafter, suckback is performed to reduce the pressure of the resin stored in front of the screw head 14, thereby preventing the resin from dripping from the tip of the injection nozzle 13. At this time, even if the screw 12 is retracted, the resin in the metering portion 18 is not removed from the screw head 14.
, The amount of resin stored in front of the screw head 14 can be prevented from fluctuating.

As a result, the amount of injected resin is constant, and short shots, burrs, and the like can be prevented from occurring in the molded product. Subsequently, when the screw 12 is advanced during the injection step, the resin stored in front of the screw head 14 tends to move backward, but the first ring 31 and the second ring 32 It is placed in the same state as at the time, and the sealing is performed.

As a result, the resin stored in front of the screw head 14 can be prevented from flowing backward, so that the amount of injected resin becomes constant and short shots, burrs, etc. occur in the molded product. Can be prevented. In addition, the resin can be fed into the cavity space of the mold at the same time when the screw 12 starts to move forward, so that the response to the melt front can be improved.

Further, the timing of sealing does not vary depending on the kneaded and dispersed state of the resin, the viscosity, the temperature, and the like, and the degree of rise of the screw speed at the start of the injection step. In addition, 35 is an opening of the first ring 31, and 45 is an opening of the second ring 32. In the present embodiment,
The backflow prevention device is operated according to a time chart as shown in FIG.

That is, when the mold is clamped by a mold clamping device (not shown), the injection process is started, and when the injection process is completed, the pressure-holding process is performed for a fixed time. And
In the mold, a cooling step is started, and during the cooling step, a measuring step, a seal, and a suck-back by an injection device are performed. Then, on the mold side, when the cooling step is completed, the mold clamping device opens and projects the mold.

Next, the driving means of the screw 12 will be described. FIG. 12 is a hydraulic circuit diagram of a driving unit according to the first embodiment of the present invention, FIG. 13 is a diagram illustrating a control device of the hydraulic circuit according to the first embodiment of the present invention, and FIG.
FIG. 4 is a diagram showing an operation table of a driving unit according to the first embodiment of the present invention. In FIG. 12, reference numeral 141 denotes an injection cylinder as driving means for moving the screw 12 (FIG. 1) forward and backward in the injection step.
Reference numeral 1 denotes a cylinder body 142 and a piston 143 disposed in the cylinder body 142 so as to be able to move forward and backward. A piston rod 146 in front of the piston 143 is connected to the screw 12. A first oil chamber 144 is formed in front of the piston 143, and a second oil chamber 145 is formed in the rear. Therefore, the oil is supplied to the first oil chamber 144 and the piston 143 is retracted by draining the oil from the second oil chamber 145, and the oil is supplied to the second oil chamber 145. The piston 143 can be advanced by draining oil from the piston.

Reference numeral 148 denotes an oil motor as driving means for rotating the screw 12 forward or backward, and in the measuring step, the oil motor 148 is driven in the forward direction to drive the screw 12 forward. Can be rotated forward. In addition, the screw 12 can be rotated in the reverse direction by driving the oil motor 148 in the reverse direction during a set period from the completion of the measurement process to the start of the injection process.

Reference numeral 149 denotes a hydraulic pressure source. The hydraulic pressure source 149 is connected to the switching valve 151 via an oil passage L-1.
-2, to the on-off valve 153, to the pressure reducing valve 154 via the oil passage L-3, and to the switching valve 155 via the oil passage L-4. Further, the switching valve 151 is provided with an oil passage L-6.
And the switching valve 152 is connected to the second oil chamber 145 of the injection cylinder 141 via an oil passage L-7.

Further, the on-off valve 153 is connected to the first oil chamber 144 of the injection cylinder 141 via an oil passage L-8, and the switching valve 155 is connected to the first oil chamber 144 via an oil passage L-9. Note that a check valve 162 is provided in the oil passage L-9. The switching valve 152 is connected to the oil motor 148 via oil passages L-10 and L-11, and the pressure reducing valve 154 is connected to the oil passage L-L.
The switching valve 156 is connected to the switching valve 156 via a pilot oil passage L-13.
3 is connected. The oil pressure source 149 and the first oil chamber 144 of the injection cylinder 141 are connected via an oil passage L-14, and a check valve 161 is provided in the oil passage L-14.

The switching valve 151 includes solenoids a and b. When the solenoid a is turned on and the solenoid b is turned off, the position A is set. When the solenoids a and b are turned on, the position B is set.
When the solenoid a is turned off and the solenoid b is turned on, the position C is taken. Then, at the position A, the oil passage L-1 and the oil passage L-7 are communicated, and the oil from the hydraulic source 149 is supplied to the second oil chamber 145 of the injection cylinder 141. At this time, the oil passage L-6 and the oil tank 160 are shut off. Further, at the position B, the oil passage L-7 and the oil tank 160 are communicated, and the oil in the second oil chamber 145 is drained. Then, at the position C, the oil passage L
-1 and the oil passages L-6 and L-7 are communicated.

The switching valve 152 has a solenoid b.
When the solenoid b is turned off, the position A is set, and when the solenoid b is turned on, the position B is set. Then, at the position A, the oil passage L-6 and the oil passage L-10 are communicated, and the oil motor 148 is driven in the forward direction. Further, at the position B, the oil passage L-6 and the oil passage L-11 communicate with each other, and the oil motor 148 is driven in the opposite direction.

The switching valve 156 has a solenoid b,
When the solenoid b is turned off, the position A is set, and when the solenoid b is turned on, the position B is set. Then, at the position A, the pilot oil passage L-13 and the oil tank 160 are communicated, and the pilot pressure applied to the on-off valve 153 is eliminated. Further, at position B, the oil passage L-12 and the pilot oil passage L-13 are communicated, and a pilot pressure is applied to the on-off valve 153.

The on-off valve 153 is connected to the pilot oil passage L
Position A is taken when pilot pressure is applied via -13, and position B is taken when pilot pressure is not applied. Then, at the position A, the oil passage L-2 and the oil passage L-8 are shut off, at the position B, the oil passage L-2 and the oil passage L-8 are communicated, and oil from the oil pressure source 149 is discharged from the injection cylinder. 141 is supplied to a first oil chamber 144.

The switching valve 155 includes a solenoid a.
Position A is taken when solenoid a is turned on, and position B is taken when solenoid a is turned off. Then, at the position A, the oil passage L-4 and the oil passage L-9 are communicated, and the hydraulic pressure source 149
Is supplied to the first oil chamber 144 of the injection cylinder 141. Further, at the position B, the oil passage L-9 and the oil tank 160 are communicated, and the oil in the first oil chamber 144 is drained.

Next, each of the switching valves 151, 152, 155,
The operation of 156 will be described. In FIG. 13, 17
Reference numeral 1 denotes a control device, and the control device 171 and each switching valve 15
1, 152, 155, and 156, drivers 172 to 175 are provided, respectively.
5, the solenoids a and b of the switching valve 151 (FIG. 1)
2) The solenoid b of the switching valve 152, the solenoid a of the switching valve 155, and the solenoid b of the switching valve 156 are turned on / off.

Then, in the measuring step, as shown in FIG. 14, the switching valve 151 is placed at the position C and the switching valve 152 is placed at the position A. The switching valve 156 is also located at the position A,
As a result, the on-off valve 153 is placed at the position B. Therefore, the oil motor 148 can be driven in the forward direction and the screw 12 can be moved backward while rotating forward. At this time, the switching valve 155 is placed at the position B.

When the measuring step is completed, the switching valve 151 is placed at the position C and the switching valve 152 is placed at the position B. The switching valve 156 is also located at the position B, and the pilot pressure
3 and the on-off valve 153 is placed in position A. Therefore, the screw 12 can be rotated in the reverse direction, and sealing can be performed by the backflow prevention device. The switching valve 15
5 is located at position B.

At this time, the screw 12 attempts to move forward, but since the oil remains in the suck-back side of the injection cylinder 141, that is, in the first oil chamber 144, the screw 12 does not move, and the measuring step is performed. Placed in completed position. In this way, the screw position is maintained. Thereafter, in the suckback, the switching valve 151 is placed at the position B, and the switching valves 152 and 155 are placed at the position A. Further, the switching valve 156 is located at the position B, and as a result, the on-off valve 153 is located at the position A. Therefore, the screw 12 can be retracted to perform suckback.

Next, in the injection step, the switching valve 151 and the switching valve 152 are set at the position A. Also, the switching valve 15
6 is also located at position A, so that on-off valve 153 is at position B
To be placed. Therefore, the screw 12 can be advanced. At this time, the switching valve 155 is in the position B
To be placed. In the present embodiment, the screw 12
The injection cylinder 141 moves the screw 12 forward and backward, and the oil motor 14 moves the screw 12 forward and reverse.
8 are used, but an electric motor may be used instead of the injection cylinder 141 and the oil motor 148.

Next, a second embodiment of the present invention will be described. FIG. 15 is a perspective view of a main part of a screw according to the second embodiment of the present invention. In the figure, reference numeral 52 denotes a screw. The screw 52 has a screw head 54 at the tip (left side in the figure) and a metering portion 55 at the rear. A spiral flight 15 is provided on the surface of the metering portion 55. Are formed, and a groove 16 is formed between the flights 15.
Is formed.

The screw head 54 has a conical head body 57 at the front and a small-diameter portion 58 at the rear, and a pair of regulating projections 64a, 64b at the front end of the small-diameter portion 58.
Are formed for a plurality of pairs (two pairs in the present embodiment). Then, a head bolt 74 passes through the screw head 54, and the screw head 54 is screwed to the metering part 55 by a screw part 65 formed at the rear end of the head bolt 74.

An annular first ring 61 is fixed to the front end of the metering portion 55, and an annular second ring 62 is arranged on the outer periphery of the small diameter portion 58 so as to be adjacent to the first ring 61. You. In order to prevent the second ring 62 from rotating together with the screw head 54, the thickness of the second ring 62 is set to be equal to the rear ends of the regulating protrusions 64a and 64b and the first ring.
Slightly smaller than the distance from the front end of the ring 61, 0.1
~ 0.2 [mm] clearance is formed,
Switching between injection and metering does not move the second ring 62 in the axial direction.

Further, the outer diameter is made slightly smaller than the inner diameter of a heating cylinder (not shown) and the inner diameter is made slightly larger than the outer diameter of the small diameter portion 58 so that the second ring 62 does not rotate together with the screw head 54. The first ring 61
Are provided at a plurality of locations in the circumferential direction of the outer peripheral edge,
And a valley 68 as a first resin flow path formed between the peaks 67.

On the other hand, the second ring 62 has an opening 69 at the center through which the small diameter portion 58 penetrates, and the valley portions 68 at a plurality of locations in the circumferential direction inside the outer peripheral edge.
A through-hole 70 as a second resin flow path is formed correspondingly. Locking claws 71, 72 are formed on the surface of the second ring 62 on the screw head 54 side so as to correspond to each pair of regulating protrusions 64a, 64b, and are disposed between the regulating protrusions 64a, 64b, respectively. Is established.

Therefore, the first ring 61 and the second ring 62 are relatively swingable, and are swingable by the swing regulating means comprising the locking claws 71, 72 and the regulating projections 64a, 64b. The range is regulated. Then, in the measuring step, when the screw 52 is rotated forward in the direction of arrow A, the first ring 61 is rotated in the same direction as the screw 52. Subsequently, the second ring 62
The screw 52 is rotated in the same direction as the screw 52 due to a frictional force generated between the ring 61 and the flow of resin generated as the first ring 61 rotates.

In this case, first, the first ring 61 is rotated first, so that a relative rotation occurs between the first ring 61 and the second ring 62, but the locking claw 72 is restricted. When the first ring 61 contacts the projection 64a,
And the second ring 62 are integrally rotated. At this time, the valley 68 of the first ring 61 and the through-hole 70 of the second ring 62 are located at the same position in the circumferential direction and communicate with each other. Moves forward through the valleys 68 and the through holes 70 and is stored in front of the screw head 54.

Thus, when the measuring step is completed,
Before the suckback, the screw 52 is reversely rotated at a rotation speed N [rpm] for a time t in a direction opposite to the arrow A direction. Then, the first ring 61 is rotated in the same direction as the screw 52, and subsequently, the second ring 62 is also rotated by the frictional force generated between the first ring 61 and the first ring 61.
Due to the flow of resin generated with the rotation of
The screw 52 is rotated in the same direction.

In this case, first, the first ring 61 is rotated first, so that a relative rotation occurs between the first ring 61 and the second ring 62.
When the 72 abuts on the regulating protrusion 64b, the first ring 61 and the second ring 62 are thereafter rotated integrally. At this time, the valley 68 of the first ring 61 and the through hole 70 of the second ring 62 are placed at different positions in the circumferential direction, are not communicated, and are sealed.

Thereafter, suckback is performed to reduce the pressure of the resin stored in front of the screw head 54, thereby preventing the resin from dripping from the tip of an injection nozzle (not shown). At this time, even if the screw 52 is retracted, the resin in the metering portion 55 does not move forward, so that the amount of resin stored in front of the screw head 54 can be prevented from fluctuating.

As a result, the amount of injected resin becomes constant, and short shots, burrs, and the like can be prevented from occurring in the molded product. When the screw 52 is rotated in the reverse direction, the screw 52 tends to move forward due to the screw effect. To prevent this, a driving unit (not shown) holds the screw 52 at the position where the measuring step is completed in the heating cylinder. I do.

Subsequently, at the time of the injection step, the screw 5
When the screw 2 is advanced, the resin stored in front of the screw head 54 tends to move backward, but the first ring 61 and the second ring 62 are placed in the same state as when sucking back, and the seal is closed. Is performed. As a result, the resin stored in front of the screw head 54 can be prevented from flowing backward, so that the amount of injected resin is constant, and short shots, burrs, and the like are prevented from occurring in the molded product. can do.

Further, the resin can be fed into the mold at the same time as the screw 52 starts to move forward, so that the response to the melt front can be improved. In addition,
The sealing timing does not vary depending on the kneaded and dispersed state of the resin, the viscosity, the temperature, and the like, and the degree of rise of the screw speed at the start of the injection step.

Next, a third embodiment of the present invention will be described. FIG. 16 is a perspective view of a main part of a screw according to the third embodiment of the present invention. In addition, about what has the same structure as 2nd Embodiment, the description is abbreviate | omitted by attaching the same code | symbol. In this case, regulation pins 84 and 85 are formed at the front end of the screw head 83 so as to protrude in the lateral direction. Also, the second ring 82
At the center, there is an opening 87 through which the screw head 83 penetrates, and a plurality of through holes 70 as second resin flow paths corresponding to the valleys 68 of the first ring 61 at a plurality of locations in the circumferential direction inside the outer peripheral edge. Is formed. A locking claw 88 is formed on the surface of the second ring 82 on the distal end side of the screw head 83 so as to correspond to each of the restriction pins 84 and 85.
a, 88b are formed to protrude. Therefore,
The first ring 61 and the second ring 82 are relatively swingable, and the swing range is regulated by a swing regulating means including locking claws 88a, 88b and regulating pins 84, 85. .

In this case, the regulating protrusion 64 is attached to the second ring 82.
a (FIG. 15) and 64b need not be formed, so that the structure of the backflow prevention device can be simplified. It should be noted that the present invention is not limited to the above-described embodiments, 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.

[0068]

As described above in detail, according to the present invention, in the backflow prevention device, a metering portion, a screw head screwed to the metering portion,
A first ring provided between the metering section and the screw head, the first ring having a first resin flow path, and the metering section and the screw head being relatively adjacent to the first ring. A second ring having a second resin flow path and a driving means for selectively rotating the screw forward and backward selectively.

When the screw is rotated forward between the first ring and the second ring, the first ring is rotated.
A swing restricting means is formed for connecting the resin flow path and the second resin flow path and for disconnecting the first resin flow path and the second resin flow path when the screw is rotated in the reverse direction. In this case, in the measuring step, when the screw is rotated forward, the first resin flow path and the second resin flow path are communicated with each other, and the resin in the metering unit is connected to the first resin flow path and the second resin flow path.
It moves forward through the resin flow path and is stored in front of the screw head.

When the measuring step is completed, the screw is rotated in the reverse direction, and the swing restricting means disconnects the first resin flow path from the second resin flow path. Therefore, afterwards, even if suckback is performed and the screw is retracted, the resin in the metering part does not move forward,
It is possible to prevent the amount of resin stored in front of the screw head from fluctuating.

As a result, the amount of injected resin is constant, and short shots, burrs and the like can be prevented from occurring in the molded product. Subsequently, when the screw is advanced during the injection step, the resin stored in front of the screw head tends to move backward, but the first ring and the second ring are in the same state as when sucking back. And sealing is done.

As a result, the resin stored in front of the screw head can be prevented from flowing backward, so that the amount of injected resin becomes constant, and short shots, burrs, etc. occur in the molded product. Can be prevented. Further, the resin can be fed into the mold at the same time as the screw is started to advance, so that the response to the melt front can be improved.

In another backflow prevention device of the present invention, the driving means rotates the screw forward during the measuring step, and reversely rotates the screw after the measuring step is completed. Hold at the process completion position. In this case, suckback can always be performed at the position where the measurement process is completed, and the injection process can be started at the position where the measurement process is completed, so that the amount of resin injected for each shot varies. Can be prevented.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part of an injection device according to a first embodiment of the present invention.

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

FIG. 3 is a front view of a first ring according to the first embodiment of the present invention.

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

FIG. 5 is a rear view of the second ring according to the first embodiment of the present invention.

FIG. 6 is a sectional view of a second ring according to the first embodiment of the present invention.

FIG. 7 is a front view showing a first ring and a second ring in a weighing step according to the first embodiment of the present invention.

FIG. 8 is a sectional view taken along line XX of FIG. 7;

FIG. 9 is a front view showing a state during an injection step of the first ring and the second ring according to the first embodiment of the present invention.

FIG. 10 is a sectional view taken along the line YY of FIG. 9;

FIG. 11 is a time chart of the backflow prevention device according to the first embodiment of the present invention.

FIG. 12 is a hydraulic circuit diagram of a driving unit according to the first embodiment of the present invention.

FIG. 13 is a diagram showing a control device of the hydraulic circuit according to the first embodiment of the present invention.

FIG. 14 is a diagram illustrating an operation table of a driving unit according to the first embodiment of the present invention.

FIG. 15 is a perspective view of a main part of a screw according to a second embodiment of the present invention.

FIG. 16 is a perspective view of a main part of a screw according to a third embodiment of the present invention.

[Explanation of symbols]

 12, 52 screw 14, 54, 83 screw head 18, 55 metering part 31, 61 first ring 32, 62, 82 second ring 37, 47, 68 valley 39 pin 49 regulating long groove 64a, 64b regulating protrusion 70 penetrating Hole 71, 72 Locking claw 84, 85 Restriction pin 88a, 88b Locking claw 142 Cylinder body 143 Piston 148 Oil motor

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Masaharu Akamatsu 1 731 Naganumaharamachi, Inage-ku, Chiba-shi, Chiba Chiba Works, Sumitomo Heavy Industries, Ltd. (56) References A) JP-A-2-622191 (JP, A) JP-A-63-87013 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) B29C 45/46-45/52 B29C 45 / 58-45/60

Claims (5)

(57) [Claims] (A) a metering portion; and (b) a screw head screwed to the metering portion.
(C) a first ring provided between the metering section and the screw head and having a first resin flow path;
Between the metering part and the screw head, disposed relatively swingably adjacent to the first ring,
A second ring provided with a second resin flow path, and (e) a drive unit for selectively rotating the screw forward and backward selectively, and (f) there is provided between the first ring and the second ring. When the screw is rotated forward, the first resin flow path and the second resin flow path are communicated, and when the screw is rotated reversely, the first resin flow path and the second resin flow path are connected. A backflow prevention device, wherein a swing restricting means for disconnecting is formed. 2. The apparatus according to claim 1, wherein the first ring and the second ring are both rotatable with respect to the screw.
3. The backflow prevention device according to item 1. 3. The backflow prevention device according to claim 1, wherein the first ring is fixed to the metering portion. 4. The backflow prevention device according to claim 1, wherein the first ring is integrated with the metering portion. 5. The measuring unit according to claim 1, wherein the driving unit rotates the screw in a normal direction during the measuring process, and rotates the screw in a reverse direction after the measuring process is completed, and holds the screw in the measuring process completed position. Backflow prevention device.