KR20000008921A - Reverse current preventing device - Google Patents

Abstract

PURPOSE: A reverse current preventing device is provided to prevent the burr and the charging defects of a molded product and to improve durability. CONSTITUTION: The reverse current preventing device has a screw(52) containing a metering unit(58) formed with groove for moving a resin to a front part and a plate type closing member which passes the front of the screw and the groove, in an opening state by a resin pressure generated in a rear part based on measuring and blocks the front of the screw and the groove in a closed state by the restoring force of the elastic member. That is, when the process of measurement is finished, the closing member blocks the front of the screw and the groove with the restoring force. Therefore, a perfect sealing can be finished before the process of injection starts.

Description

Backflow prevention device

The present invention relates to a backflow prevention device.

Conventionally, an injection molding machine has an injection device, and is installed in the heating cylinder of the injection device so that the screw can freely rotate or move forward and backward, and the screw can be rotated or moved forward and backward by a driving means. Then, the screw is retracted while the screw is rotated in the weighing step, the resin dropped from the hopper is melted and accumulated in front of the screw, and the screw is advanced in the injection step to inject molten resin from the injection nozzle.

1 is a cross-sectional view of main parts of a conventional injection apparatus.

In the figure, 11 is a heating cylinder, and the heating cylinder 11 has an injection nozzle 13 at the front end (left side of the drawing). In the heating cylinder 11, the screw 12 is provided so as to be freely rotatable, forward, and retractable, and the screw 12 can be rotated or moved forward and backward by a driving means (not shown). In addition, an injection cylinder, an electric motor, and the like are usually used as the driving means.

The screw 12 extends backward in the heating cylinder 11 (right side of the drawing), is connected to the driving means at the rear end, and is provided with a screw head 14 at the front end. In addition, 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 place behind the heating cylinder 11, and pellet-shaped resin is introduced into the hopper.

When the screw 12 is retracted while the screw 12 is rotated by the driving means during the weighing process in the injection apparatus having the above-described configuration, the resin in the hopper falls in the heating cylinder 11 and moves forward in the groove 16 (in the drawing). To the left).

In addition, a heater (not shown) is provided on the outer circumference of the heating cylinder 11, and the heater can be heated to melt the resin in the groove 16 by the heater. Therefore, when only a predetermined amount is retracted while the screw 12 is rotated, the molten resin of the amount required for injection is accumulated in front of the screw 12.

In this way, when the metering process is completed, a suc back is performed so that the resin does not drop from the front end of the injection nozzle 13, and the screw 12 is not rotated and only a very small amount of retreat is retreated again.

Next, when the screw 12 is advanced by the driving means in the injection process, the resin accumulated in front of the screw 12 is injected from the injection nozzle 13 and filled in the cavity space of the mold apparatus (not shown). .

By the way, the backflow prevention apparatus is installed so that the resin accumulated in front of the screw 12 at the time of the injection process does not flow back.

For this reason, the screw head 14 has a conical head body 21 at the front, a small diameter portion 19 at the rear, and the small diameter portion 19 has a male screw (not shown) extending rearward. . The screw head 14 is fixed to the screw 12 by screwing the male screw and a female screw (not shown) formed at the front end of the screw 12. In addition, a round backflow prevention ring 20 is installed on the outer circumference of the small diameter portion 19, and a resin flow passage 24 is formed between the small diameter portion 19 and the backflow prevention ring 20. . Then, the seal 22 is installed at the front end of the metering unit 18 so as to be freely attached to the rear end of the backflow prevention ring 20.

Therefore, when the screw 12 is advanced in the injection process, the resin accumulated in front of the screw 12 tries to flow back, but the backflow prevention ring 20 is relatively backward with respect to the screw 12 due to the resin pressure. By moving, the rear end of the non-return ring 20 is in contact with the seal 22 and sealed. As a result, backflow of the resin accumulated in front of the screw 12 can be prevented.

Meanwhile, when the screw 12 is retracted while rotating the screw 12 during the weighing process, the backflow prevention ring 20 is moved forward relative to the screw 12 by the resin pressure so that the front end of the backflow prevention ring 20 is moved to the head body. Although it touches the rear end of 21, since the cutting part 25 extended in the axial direction is formed in many places around the head main body 21, movement of resin is not disturbed.

However, in the conventional non-return device, the screw 12 is advanced during the injection process so that the rear end of the non-return ring 20 abuts against the seal 22 to seal, until the sealing is finished. Resin flows back by the amount which the screw 12 advanced.

In addition, it is necessary to make the small diameter portion 19 longer than the backflow prevention ring 20 so that a sufficient amount of resin flows between the backflow prevention ring 20 and the seal 22 in the resin flow passage 24 in the metering process. Since the amount of movement of the backflow prevention ring 20 is increased so that it is sealed, the amount of resin flowing back becomes large.

In addition, the timing at which the sealing ends is varied when the molding conditions for setting the initial state of the kneading state, dispersion state, viscosity, temperature, etc. of the resin and the injection speed at the start of injection are different, and also in the same molding conditions. There are times.

Therefore, since the amount of resin flowing back is not constant and the injection peak pressure is not constant, burrs, short shots, and the like occur in the molded article.

In addition, the time required for releasing the seal at the start of the metering process becomes long, and excess heat is generated due to plasticization of the resin.

Thus, there is provided a backflow prevention device in which the screw 12 is reversely rotated once when the metering step is completed, so that the rear end of the backflow prevention ring 20 is brought into contact with the seal 22 and sealed.

However, in this kind of backflow prevention device, it is necessary to provide a mechanism for engaging the rear end of the backflow prevention ring 20 with the seal 22, which not only complicates the structure of the screw head 14, Control of the drive means is complicated because it is necessary to reverse 12).

Thus, a backflow prevention device using a ball check backflow check valve has been provided.

Figure 2 is a view showing a non-return device using a ball check check valve.

In the drawing, 11 is a heating cylinder, 32 is a screw, and the screw 32 is screwed to the metering part 33 and the metering part 33, and has a screw head 34 having the same outer diameter as the metering part 33. It consists of The screw 32 extends rearward (right side of the drawing) in the heating cylinder 11, and a spiral flight 35 is formed on the surface of the metering part 33, between the flights 35. Grooves 36 are formed.

The screw head 34 is opened at a front end (left side of the drawing) and extends rearward, and a valve chamber formed by communicating with the resin channel 41 at the rear end of the resin channel 41. Has 43. In addition, the metering part 33 has a resin flow passage 46 formed at the front end and extended rearward, and a resin flow passage 47 formed to pass through the resin flow passage 46 and the groove 36. A valve seat 45 is formed at the front end of the resin flow passage 46, and a ball 49 as a non-return valve is provided on the valve seat 45 by the elastic force of the coil spring 50.

In the countercurrent prevention device of the above configuration, the ball 49 moves forward against the elastic force of the coil spring 50 by the resin pressure when the screw 32 is retracted while the screw 32 is rotated by a driving means not shown in the weighing process. To the left). Therefore, the resin advancing in the groove 36 passes through the resin flow passages 47 and 46, the valve chamber 43, and the resin flow passage 41 in order, and accumulates in front of the screw 32.

Subsequently, when the screw 32 is advanced in the injection process, the resin accumulated in front of the screw 32 tries to flow back, but the ball 49 is pressed against the valve seat 45 by the elastic force of the coil spring 50. Since it is broken and sealed, backflow of the resin accumulated in front of the screw 32 can be prevented.

Therefore, the filling time required for filling is shortened, and the temperature of the resin does not decrease during filling, or the viscosity of the resin does not increase. In addition, since it is not necessary to form a small diameter portion in the screw head 34, the screw head 34 can be prevented from being damaged in the initial state in which plasticization of the resin is started.

In addition, since the time required for releasing the seal is not long when the metering process is started, excess heat generation due to plasticization of the resin does not occur.

By the way, in the backflow prevention device of the above structure, since the coil spring 50 is used for sealing, not only the stress generated in the coil spring 50 is large, but also the resin of the high temperature or high pressure is applied to the coil spring 50. Will come in contact with Therefore, the coil spring 50 deteriorates in a short time and the durability of a backflow prevention device falls. In addition, since each of the resin channels 41, 46, 47 is narrow and complicated, shear heat generation occurs when resin flows through the resin channels 41, 46, 47. do.

The present invention solves the problems of the conventional backflow prevention device, can prevent the occurrence of burrs, filling defects, etc. in the molded article, less occurrence of excess heat and shear heat generation, and also to increase the durability backflow It is an object to provide a prevention device.

1 is a main cross-sectional view of a conventional injection apparatus,

Figure 2 is a view showing a backflow prevention device using a ball check backflow check valve,

3 is a schematic view of a backflow prevention device of a first embodiment of the present invention;

4 is a cross-sectional view taken along line X-X of FIG. 3;

5 is a schematic view of a backflow preventing device according to a second embodiment of the present invention;

6 is a schematic view of a backflow prevention device according to a third embodiment of the present invention;

7 is a front elevational view of the main portion of the backflow prevention device according to the third embodiment of the present invention;

8 is a schematic diagram of a head body according to a fourth embodiment of the present invention.

<Description of the symbols for the main parts of the drawings>

51: heating cylinder 52: screw

54, 154: screw head 58, 158: metering part

59, 282: sealing part 61, 161: resin hole

63, 81, 163: leaf spring 63a, 81a, 163a: blocking part

63b, 81b, 163b: elastic support 159: sealing

181: head body

The backflow prevention device of the present invention has at least a screw having a metering portion formed with a groove for moving the resin forward, and a plate-shaped closing member.

Then, the closing member is placed in the open state by the resin pressure generated in the rear in accordance with the metering, through the front and the groove of the screw, and is placed in the closed state by the restoring force by the elastic material, so that the front and the groove of the screw To block.

In this case, when the metering process is completed, the closing member is in the closed state by the restoring force to block the front of the screw and the groove. Therefore, the sealing can be completed completely before the injection process is started. Moreover, since the timing at which the front of the screw and the groove are blocked does not change, not only the filling amount of the resin into the cavity space can be stabilized, but also the inconsistency of the injection peak pressure can be suppressed. As a result, generation of burrs, charging failures, and the like can be prevented. Moreover, it can suppress that the weight of a molded article is not fixed.

The pressure in the vicinity of the injection nozzle can be sufficiently lowered only by retreating the screw about 1/3 of the conventional time at the time of suc back. Therefore, it is possible to sufficiently suppress the inflow of air in accordance with the seat back. The resin can be prevented from dripping down.

In addition, since the resin pressure in front of the screw can be sufficiently high at a time of about several tens of kPa after the injection process is started, the filling time is shortened, and the temperature of the resin is low or the viscosity of the resin is high during the filling.

In addition, since the time required for releasing the seal does not become long when the metering process is started, excessive heat generation due to plasticization of the resin is less likely to occur.

And since the closing member is plate-shaped, the stress generated in the closing member can be reduced. Therefore, it is possible to prevent the closing member from deteriorating in a short time, thereby increasing the durability of the backflow prevention device.

In another non-return device of the present invention, the closing member is installed at the end face of the metering part.

In this case, since the closure member is supported by the metering portion, the closure member is not deformed by the resin pressure during the injection process. Therefore, the durability of the backflow prevention device can be improved. Further, not only can the resin flow path be widened, but also can be simplified, so that no heat generation occurs when the resin flows, and color changeability can be improved.

In another non-return device of the present invention, a screw head is provided at the front end of the metering part.

In another non-return device of the present invention, the closure member is provided on the screw head.

In another non-return device of the present invention, the closure member is formed at least in part by an elastic material, integrally formed with the blocking portion formed between the front of the screw and the groove and the blocking portion, and the blocking portion is closed. It is composed of an elastic support for elastic support to be.

In another backflow prevention device of the present invention, the entirety of the closure member is formed of an elastic material.

In another non-return device of the present invention, the closure member is a leaf spring.

In another backflow preventing device of the present invention, the closing member covers the resin hole formed in the front end of the metering portion in the closed state.

In another non-return device of the present invention, the closure member covers the groove of the front end of the metering portion in the closed state.

In another backflow preventing device of the present invention, the closing member covers the resin hole formed in the front end of the metering portion in the closed state.

In another non-return device of the present invention, the screw head has a seal for sealing the front of the screw and the groove at the rear of the closure member.

In another non-return device of the present invention, the screw head comprises a head body having a fitting portion and a seal fitted to an outer circumference of the fitting portion and serving as the sealing portion, and between the sealing and the head body in the axial direction. A gap of 10 µm or more and 0.5 mm or less is formed in the gap.

In this case, not only the eccentricity of the screw generated by advancing the screw in the injection process is absorbed by the gap, but also the eccentricity is prevented by the sealing after the eccentric is absorbed. Therefore, it is possible to prevent the screw from being pressed against the inner wall of the heating cylinder and to suppress the occurrence of sticking. In addition, wear can be suppressed from occurring in the outer peripheral portion of the screw head.

In another backflow prevention device of the present invention, the heat treatment temperature after quenching of the elastic material is 400 ° C or higher.

In this case, since the closing member is not deteriorated by the high temperature resin, the durability of the backflow prevention device can be improved.

In another backflow prevention device of the present invention, a labyrinth is formed on the outer surface of the sealing portion.

In this case, the sealing part and the inner wall of the heating cylinder slide smoothly by the grabber.

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention is described in detail, referring drawings. 3 is a schematic view of a backflow prevention device according to a first embodiment of the present invention, and FIG. 4 is an X-X cross-sectional view of FIG. 3.

In the figure, 51 is a heating cylinder, and the heating cylinder 51 has an injection nozzle not shown at the front end (left side of the drawing). In the heating cylinder 51, the screw 52 is provided so as to be freely rotatable, forward, and retractable, and the screw 52 can be rotated or moved forward and backward by a driving means (not shown). In addition, an injection cylinder, an electric motor, and the like are usually used as the driving means.

The screw 52 extends rearward (right side of the drawing) in the heating cylinder 51, is connected to the driving means at the rear end, and has a screw head 54 and a metering portion 58. In this case, a male screw (not shown) is formed at the rear end of the screw head 54, and the screw head 54 is metered by screwing the male screw and the female screw (not shown) formed at the front end of the metering portion 58. 58). In addition, the screw head 54 may be formed integrally with the metering portion 58.

Moreover, the spiral flight 55 is formed in the surface of the metering part 58, and the groove | channel 56 is formed between the flights 55. As shown in FIG.

A hopper (not shown) is provided at a predetermined place behind the heating cylinder 51, and pellet-shaped resin is introduced into the hopper. In addition, a sealing portion 59 having the same outer diameter as the flight 55 is formed at the front end of the metering portion 58 along the outer circumference. In addition, a seal (not shown) may be fitted to the front end of the metering unit 58 as necessary.

At least one fan-shaped resin hole 61 is formed in the circumferential direction of the sealing portion 59 to allow the front of the sealing portion 59 and the grooves 56 to pass through. In order to cover the resin hole 61, a fan-shaped leaf spring 63 as a closing member is provided at the front end of the metering portion 58, and one end of the leaf spring 63 is screwed by a screw 64. It is fixed to the seal 59. Therefore, the groove 71 is formed in the sealing portion 59 so that one end of the leaf spring 63 is inserted into the groove 71.

The leaf spring 63 is integrally formed with the blocking portion 63a and the blocking portion 63a formed in correspondence with the resin hole 61 between the front of the screw 52 and the metering portion 58. It is formed of an elastic support portion 63b for elastically supporting the blocking portion 63a to be in a closed state. In this embodiment, the leaf spring 63 is used as the plate-shaped closing member, and both the blocking portion 63a and the elastic support portion 63b are formed of an elastic material. Only at least one of the closing members is formed of the elastic material. It may be formed.

In that case, only the elastic support portion 63b is formed of an elastic material, and the blocking portion 63a is formed of an inelastic material.

Therefore, the leaf spring 63 is normally placed in the closed state shown by the solid line in FIG. 3 to directly block the front of the screw 52 and the groove 56, and the resin pressure in the groove 56 is reduced by the screw 52. When it is higher than the front resin pressure, it bends and it is in the open state shown by the broken line of FIG. 3, and the front of the screw 52 and the groove | channel 56 pass.

In addition, except for a special high temperature resin, since the normal resin has a melting point of 200 to 380 ° C, the temperature at which the quenched metal is appropriately heat-treated again in order to increase the strength of the quenched metal so as not to lose elasticity even at a high temperature as the elastic material. Those higher than the melting point, such as 400 ° C. or higher, are used. In this embodiment, an inconel having a heat treatment temperature of 514 ° C or higher after quenching is used as the elastic material. In addition, in the injection molding machine using resin having a high melting point, the leaf spring 63 may be formed of an elastic material such as zirconia ceramic.

Thus, since the leaf spring 63 is used, the stress which arises in the leaf spring 63 can be made small, and since the heat processing temperature after quenching is used as the said elastic material above the melting point of resin, the said The leaf spring 63 may not deteriorate in a short time, thereby increasing the durability of the backflow prevention device. In addition, since the leaf spring 63 directly blocks the front of the screw 52 and the groove 56, the responsiveness of the backflow prevention device can be improved.

In addition, the leaf spring 63 is formed with a concave portion 72 adjacent to the fixing portion by the screw 64 so as to bend easily.

When the screw 52 is retracted while the screw 52 is rotated in the direction of arrow M by the driving means in the counter flow prevention device of the above configuration, the pellet-shaped resin in the hopper falls in the heating cylinder 51, and the groove 56 Will move forward within.

In addition, a heater (not shown) is provided at an outer circumference of the heating cylinder 51, and the heating cylinder 51 is heated by the heater. Therefore, the resin is melted while advancing in the grooves 56, passes through the resin holes 61, bends the leaf spring 63 to open, and flows out in front of the sealing portion 59. In this manner, if the predetermined amount is retracted while the screw 52 is rotated, the molten resin in the amount required for injection is accumulated in front of the screw 52.

When the metering process is completed, the rotation of the screw 52 is stopped. At this time, the resin pressure in the groove 56 is lowered, and the resin pressure in the groove 56 and the resin pressure in front of the screw 52 are almost reduced. Becomes the same. Therefore, the leaf spring 63 is returned by the restoring force of the elastic support 63b, is placed in a closed state, and seals the resin hole 61 by closing.

And the back and back is performed so that resin may not fall down from the front end of the injection nozzle, and the screw 52 is not rotated and only a very small amount is retracted again.

Next, when the screw 52 is advanced by the driving means during the injection process, the resin accumulated in front of the screw 52 is injected from the injection nozzle and filled into the cavity space of the mold (not shown). At this time, the resin accumulated in front of the screw 52 tries to flow back, but since the leaf spring 63 is already closed and the resin hole 61 is closed, the resin accumulated in the front of the screw 52 The resin can be prevented from flowing back.

In this manner, since the leaf spring 63 is closed and the sealing is finished before the injection process is started, the timing at which the sealing is finished does not change. Therefore, not only the filling amount of the resin into the cavity space can be stabilized, but also burrs can be prevented from occurring.

Furthermore, since the resin pressure in front of the screw 52 can be sufficiently high at the time of several tens of kPa after the injection process is started, the filling time is shortened, the temperature of the resin is lowered during filling, or the viscosity of the resin is increased. Does not rise.

Moreover, since it is not necessary to form a small diameter part in the said screw head 54, it can prevent that the screw head 54 is damaged.

In addition, since the leaf spring 63 is supported by the seal 59 during the injection process, the leaf spring 63 is not deformed due to the resin pressure. Therefore, the durability of the backflow prevention device can be improved. In addition, since the resin hole 61 can be widened and simplified, the shear heat generation does not occur when the resin flows through the resin hole 61, and color changeability can be improved.

In addition, since the time required for releasing the seal is not lengthened at the start of the metering process, the excess heat generation due to plasticization of the resin is eliminated.

Next, a second embodiment of the present invention will be described.

5 is a schematic view of a backflow prevention device according to a second embodiment of the present invention. In addition, about the structure similar to 1st Embodiment, the description is abbreviate | omitted by attaching | subjecting the same code | symbol.

In this case, a concave surface 80 is formed at the front end of the metering portion 158 of the screw 52, and the dish-shaped leaf spring 81 as a plate-shaped closing member abuts on the concave surface 80. The elastic support portion 81b of the leaf spring 81 is fixed to the metering portion 158 by a screw 82. The groove 56 of the front end of the metering portion 158 is covered by the blocking portion 81a formed at the outer circumferential edge of the leaf spring 81.

When the screw 52 is retracted while the screw 52 is rotated by the driving means (not shown) in the counter flow prevention device having the above-described configuration, the resin is melted while advancing in the groove 56, and the leaf spring 81 is bent and opened. And flows in front of the leaf spring 81 through the blocking portion 81a and the heating cylinder 51. In this way, the amount of molten resin required for injection is accumulated in front of the screw 52. In addition, when the leaf spring 81 is placed in an open state, the outer circumferential edge is waved in a flare shape.

When the metering process is completed, the rotation of the screw 52 is stopped, but at this time, the resin pressure in the groove 56 decreases, and the resin pressure in the groove 56 and the resin pressure in front of the screw 52 are almost the same. Lose. Therefore, the leaf spring 81 is returned by the restoring force of the elastic support 81b, and is closed and sealed.

Next, a third embodiment of the present invention will be described.

6 is a schematic view of a backflow prevention device according to a third embodiment of the present invention, and FIG. 7 is a front view of the main portion of the backflow prevention device according to a third embodiment of the present invention.

In the figure, 51 is a heating cylinder, and the heating cylinder 51 has an injection nozzle (not shown) at the front end (left side of the drawing). In the heating cylinder 51, the screw 52 is installed so as to rotate freely and move forward and backward, and the screw 52 can be rotated or moved forward and backward by an unshown driving means. . In addition, an injection cylinder, an electric motor, and the like are usually used as the driving means.

The screw 52 extends rearward (right side of the drawing) in the heating cylinder 51 and is connected to the driving means at the rear end, and has a screw head 154 and a metering portion 58. A male screw 154a is formed at the rear end of the screw head 154, and the screw head 154 is metered by screwing the male screw 154a and the female screw 52a formed at the front end of the metering part 58. It is fixed to the part 58. In addition, the screw head 154 may be formed integrally with the metering portion 58.

Moreover, the spiral flight 55 is formed in the surface of the metering part 58, and the groove | channel 56 is formed between the flights 55. As shown in FIG.

A hopper (not shown) is provided at a predetermined place behind the heating cylinder 51, and pellet-shaped resin is introduced into the hopper.

In addition, the screw head 154 is installed in the center of the head body 181, the head body 181 is to slide between the inner wall of the heating cylinder 51 to move the front of the screw 52 and the groove 56 Sealing 159 as a sealing part for sealing the seal, a ring-shaped stopper 185 for preventing the sealing 159 from falling off in front of the sealing 159 and a plate-shaped closing member provided at the front end of the head body 181. It has a pair of leaf spring 163 as. In addition, the head body 181 has a small diameter screwing portion 182 for screwing the stopper 185 to a front end portion, and a middle diameter fitting of the sealing portion 159 to the outer circumference of the center portion. A large diameter flange portion 84 is provided at the portion 83 and the rear end portion. The seal 159 is fitted to the outer circumference of the fitting portion 83, and then is attached to the head body 181 by coupling the stopper 185 to the screw coupling portion 182. In addition, between the seal 159 and the stopper 185, the fitting portion 83, and the flange portion 84, a very small gap 86 is formed in the radial direction and the axial direction. Therefore, wear can be prevented between the sealing 159 and the head body 181 due to the rotation of the screw 52. Further, the gap 86 in the radial direction is 0.2 mm or more in total in the radial direction, and the gap 86 in the axial direction is 10 µm or more and 0.5 mm or less, preferably 50 µm or more and 0.2 mm or less in total.

A resin hole 161 is formed in two circumferential directions of the head body 181 to allow the front of the screw 52 and the groove 56 to pass therethrough. The resin hole 161 is opened toward the metering portion 58 at the outer circumferential edge portion of the flange portion 84, extends inclined toward the center in the flange portion 84, and then the fitting portion ( 83) and axially forward within the screwing portion 182 and open at the front end face of the screwing portion 182. In addition, the leaf spring 163 is installed to cover the resin hole 161 on the front end face of the screw coupling portion 182, and one end of the leaf spring 163 is connected to the stopper by a screw 164. 185).

In addition, the leaf spring 163 is formed integrally with the blocking portion 163a and the blocking portion 163a corresponding to the resin hole 161 and elastically supports the blocking portion 163a to be in a closed state. It is formed integrally with the elastic support portion 163b and its elastic support portion 163b and comprises a fixing portion 163c for fixing the leaf spring 163 to the stopper 185. In the present embodiment, the leaf spring 163 is used as the plate-shaped closing member, and all of the blocking portion 163a, the elastic support portion 163b and the fixing portion 163c are formed of an elastic material, but only a part of the closing member is used. May be formed of an elastic material. In that case, only the elastic support part 163b is formed of an elastic material, and the blocking part 163a and the fixing part 163c are formed of an inelastic material. In addition, the leaf spring 163 is formed with a recess 17 between the elastic support portion 163b and the fixing portion 163c to bend easily.

Therefore, the leaf spring 163 is normally placed in the closed state shown by the solid line in FIG. 6 to directly block the front of the screw 52 and the groove 56, and the resin pressure in the groove 56 is the front of the screw 52. When the resin pressure is higher than the resin pressure, it bends to the open state indicated by the broken line in FIG. 6 to allow the front of the screw 52 and the groove 56 to pass through.

In addition, except for the special high temperature resin, since the ordinary resin has a melting point of 200 to 380 ° C, the heat treatment temperature after quenching is higher than the melting point of the resin, for example, 400 ° C or more so that the elastic material does not lose elasticity even at high temperatures. Is used. In this embodiment, an Inconel having a temperature of 514 ° C. or higher is appropriately heat-treated again to increase the strength of the quenched metal as an elastic material. In an injection molding machine using a resin having a high melting point, the leaf spring 163 may be formed of an elastic material such as zirconia ceramic.

Thus, since the leaf spring 163 is used, the stress which arises in the leaf spring 163 can be made small, and since the heat processing temperature after quenching is used as the said elastic material, since the melting point of resin is used, the said The leaf spring 163 is not deteriorated in a short time can increase the durability of the backflow prevention device. In addition, since the leaf spring 163 directly blocks the front of the screw 52 and the groove 56, the responsiveness of the backflow prevention device can be increased.

When the screw 52 is retracted while the screw 52 is rotated by the driving means in the counter flow prevention device having the above-described configuration, the pellet-shaped resin in the hopper falls into the heating cylinder 51 and moves forward in the groove 56. 6, to the left). The heater (not shown) is provided in the outer periphery of the said heating cylinder 51, and the heating cylinder 51 is heated by the heater. Therefore, the resin melts while advancing in the grooves 56, passes through the resin holes 161, bends the leaf spring 163, and opens to flow out of the front of the screw 52. In this way, when the screw 52 is retracted while the screw 52 is rotated, the amount of molten resin required for injection is accumulated in front of the screw 52. Moreover, the resin pressure in the said groove | channel 56 at the time of a measuring process becomes about 150 kgf / cm <2> at maximum.

When the metering process is completed, the rotation of the screw 52 is stopped, but at this time, the resin pressure in the groove 56 decreases, and the resin pressure in the groove 56 and the resin pressure in front of the screw 52 are almost the same. Lose. Therefore, the leaf spring 163 is returned by the restoring force of the elastic support 163b to be in a closed state to close the resin hole 161 and to block the front of the screw 52 and the groove 56. That is, the sealing can be completed completely before the injection process is started.

Then, the back and back are performed so that the resin does not fall down from the tip of the injection nozzle, and the screw 52 is not rotated, and only a very small amount is retracted again.

Next, when the screw 52 is advanced by the driving means during the injection process, the resin accumulated in front of the screw 52 is injected from the injection nozzle and filled in the cavity space of the mold apparatus (not shown). At this time, the resin accumulated in front of the screw 52 tries to flow back, but the leaf spring 163 is already in the closed state, and the resin hole 161 is closed, so that the front of the screw 52 and the groove 56 are closed. Since it is blocked, the resin accumulated in front of the screw 52 can be prevented from flowing back.

As such, when the weighing process is completed, the leaf spring 163 is closed by the restoring force and the front of the screw 52 and the groove 56 are blocked, so that the sealing is completely completed before the injection process is started. The timing at which the front of the screw 52 and the groove 56 are blocked does not vary.

Therefore, not only the filling amount of the resin into the cavity space can be stabilized, but also the inconsistency of the injection peak pressure can be reduced to 1/2 of the conventional one, and the occurrence of burrs, filling failures, and the like can be prevented. And when polyethylene is used as resin, the scattering delta / X (average value of x) which arises in the weight of a molded article can be made into 0.17%-0.03%.

In addition, since the pressure in the vicinity of the injection nozzle can be sufficiently lowered only by retreating the screw 52 about one-third of the conventional time at the time of back seating, it is possible to sufficiently suppress the inflow of air along the back seating seat. Can be prevented from falling down.

Furthermore, since the resin pressure in front of the screw 52 can be sufficiently high at the time of several tens of kPa after the injection process is started, the filling time is shortened, the temperature of the resin is lowered during filling, or the viscosity of the resin is increased. Does not rise.

In addition, since the time required for releasing the seal is not long when the metering process is started, excess heat generation due to plasticization of the resin does not occur.

As the screw 52 is advanced during the injection process, reaction force by the resin is added to the screw head 154, and the screw 52 is eccentric by the reaction force. Thereby, the screw 52 is pressed against the inner wall of the heating cylinder 51, and sticking becomes easy. By the way, since the gap 86 is formed between the sealing 159 and the stopper 185, the fitting portion 83 and the flange portion 84, not only the eccentricity of the screw 52 is absorbed, After the eccentricity is absorbed, further eccentricity is prevented by the sealing 159. Therefore, the screw 52 can be prevented from being pressed by the inner wall of the heating cylinder 51, and it can suppress that a sticking generate | occur | produces. In addition, wear can be suppressed from occurring in the outer peripheral portion of the screw head 154. In addition, the labyrinth may be formed to improve the sliding property of the outer surface of the seal 159.

Next, a fourth embodiment of the present invention will be described.

8 is a schematic view of the head body of the fourth embodiment of the present invention.

In this case, 281 is the head body, and the front end of the head body 281 (left end of the drawing) slides with the inner wall of the heating cylinder 51 (Fig. 6), and the front of the screw 52 and the groove A seal 282 for sealing 56 is formed, and a labyrinth 283 is formed to improve the sliding property on the surface of the seal 282.

Therefore, the inner part of the sealing part 282 and the heating cylinder 51 slides and moves smoothly.

In addition, this invention is not limited to the said embodiment, It can variously deform | transform based on the meaning of this invention, and does not exclude them from the scope of this invention.

According to the present invention, sealing can be completed completely before the injection process is started. Moreover, since the timing at which the front of the screw and the groove are blocked does not change, not only the filling amount of the resin into the cavity space can be stabilized, but also the inconsistency of the injection peak pressure can be suppressed. As a result, generation of burrs, charging failures, and the like can be prevented. Moreover, it can suppress that the weight of a molded article is not fixed.

Claims (13)

At least a screw having a metering portion formed with a groove for moving the resin forward, and a plate-shaped closing member, and the closing member is placed in an open state by a resin pressure generated at the rear according to the metering, And through the groove, and placed in a closed state by a restoring force by an elastic material to block the front of the screw and the groove. The backflow prevention device according to claim 1, wherein the closing member is installed at a cross section of the metering part. The backflow preventing device according to claim 1, wherein a screw head having the plate-shaped closing member is installed at a front end of the metering part. The method of claim 1, wherein the closing member is formed at least in part by an elastic material, and is formed integrally with the blocking portion and the blocking portion formed between the front of the screw and the groove and the elastic support so that the blocking portion is in a closed state Backflow prevention device consisting of an elastic support. The backflow preventing device according to claim 1, wherein the entirety of the closure member is formed of an elastic material. 6. The non-return device of claim 5, wherein the closure member is a leaf spring. 3. The backflow preventing device according to claim 2, wherein the closing member covers the resin hole formed at the front end of the metering part in the closed state. The backflow preventing device of claim 2, wherein the closing member covers a groove of a front end of the metering part in a closed state. 4. The backflow prevention device according to claim 3, wherein the closure member covers the resin hole formed at the front end of the screw head in the closed state. 4. The backflow preventing device according to claim 3, wherein the screwhead has a seal for sealing the front of the screw and the groove at the rear of the closure member. 11. The screw head according to claim 10, wherein the screw head comprises a head body having a fitting portion and a seal fitted to the outside of the fitting portion, and is made of a sealing portion, and at least 10 mu 0.5 between the sealing and the head body in the axial direction. Backflow prevention device with a gap less than ㎜. The backflow preventing device according to claim 1, wherein the heat treatment temperature after quenching of the elastic material is 400 ° C or more. The backflow preventing device according to claim 10, wherein labyrinth is formed on an outer surface of the seal.