JPH04189119A - Check ring for resin molding screw - Google Patents

Abstract

PURPOSE:To perform precisely injection of a fixed quantity of molten resin by eliminating completely a back current of the molten resin, by a method wherein permanent magnets are arranged in the direction of the shaft center of a screw by facing on a rear region of a check ring having a nonmagnetic substance and a front region of a screw main body, and the permanent magnets are arranged by separating them from one another so that N poles are positioned alternately in circumferential directions each. CONSTITUTION:At the time of measurement, a check ring 5 is pressed against the end surface 3a of a screw head 3 by high resin pressure through a screw main body 2 side and a rear region 11 of a check ring and permanent magnet 18 arranged in a front region 12 of a screw main body are held their condition by generating identical magnetism. Then measurement of molten resin is completed and at the time of the starting of injection, simultaneously with suspension of a rotation of the screw main body 2 a pressure gradients of the screw main body 2 side and a spatial part side of a front part of the screw head become low. Since the permanent magnet 18 generates a different magnetism and the check ring 5 is pressed against the front part 12 of the screw main body quickly, a back current of the molten resin can be prevented completely.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The object of the present invention is to promptly and reliably perform the check operation of the check mechanism at the start of the injection operation.

[Prior art] Fig. 6 and Fig. 7 are conventional examples, and Fig. 6:':,
FIG. 7 is a sectional view showing the overall configuration of the injection molding machine, and FIG. 7 is a partially cutaway front view of the screw tip.

In FIG. 6, a heating cylinder 1 equipped with a heater (not shown)
A screw body 2 is inserted within the screw body, and this screw body 2 is rotationally driven by a drive device 19 such as a hydraulic motor through gears 15 and 16. Further, the screw body 2 is inserted into the chamber so as to be movable in the front and back direction, and the rear end of the screw body 2 is fixed to a hydraulic ram 20, and the screw body 2 is inserted into a hydraulic cylinder 22 that accommodates this ram 20. It is possible to move forward inside the cylinder 1 by applying hydraulic pressure.

An input port 24 for inserting a plastic material such as a synthetic resin is formed on the side surface of the heating cylinder 1, and a hopper 26 is installed. When plastic raw materials are introduced from this hopper 26,
Screw body 2 rotated by drive PI M 19
The plastic raw material is sent to the tip of the heating cylinder 1 without being kneaded by the guiding groove, and is stored in the space 28 surrounded by the tip of the heating cylinder 1 and the tip of the screw body 2. At the same time, the screw body 2 receives a reaction force from the stored plastic material and gradually moves backward.

When a predetermined amount of the plastic material remains in the space 28, hydraulic pressure is introduced into the hydraulic cylinder 22, the screw body 2 is advanced, and the plastic material in the space 28 is removed from the tip of the heating cylinder 1 into a mold (not shown). z) Inject inside.

Therefore, in the present invention, a mechanism is installed at the tip of the screw body 2 to prevent the plastic material from flowing back in the space 28. The configuration of this backflow prevention mechanism will be explained below using FIG. 7.

In FIG. 7, the check ring 5 is attached to the shaft 4 when the screw/bed 3 is fixed to the front end of the screw body 2.
a fitting device, which allows a cylindrical check ring 5 loosely fitted into the holding cylinder 1 to be slid back and forth 10,000 times; For assembly, a direct molten resin communication hole 7 is provided between the inner circumferential surface of the check ring 5 and the circumferential surface of the shaft 4, so that the molten resin flows from the screw body 2 side to the front of the screw/head 3. Narumi has a configuration that allows for flow.

Further, on the front end surface 9 of the check ring, protrusions 1o are provided at predetermined intervals.
are provided, so that even if the check ring 5 is pressed against the screw head 3, a resin passage is formed from the front communication port 14 to the rear communication port 13 via the molten resin communication hole 7. ing.

The opening of the molten resin communication hole 7 in the rear end face 11 of the check ring is arranged so that its entire area faces the front face 12 of the screw body, and the opening part of the molten resin communication hole 7 in the rear end face 11 of the check ring faces the front face 12 of the screw body.
When it comes into contact with 2, it is completely closed.

When the molten resin is plasticized and weighed backwards (hereinafter referred to as "backward metering time"), the check ring 5 is pressed forward by the flow resistance of the molten resin, and the rear communication port 13, the molten resin communication hole 7, and Screw l pet 3 through the front communication port 14
being pushed forward.

During injection, while the screw body 2 and screw head 3 move forward as one, only the check ring 5 remains and closes the rear communication port 13 (the backflow of the molten resin is prevented).

[Problems to be Solved by the Invention] In general, the check ring 5 prevents the molten resin from flowing smoothly during metering, that is, when the screw body 2 rotates and retreats to extrude the molten resin in front of the screw head 3. Although it is necessary to allow the molten resin to pass through, it is required to prevent the molten resin from flowing back during injection.

If the operation of this reverse ring 5 is slow and uncertain, the amount of molten resin injected will be uneven, resulting in short shots or overpacking of the product, which will reduce the performance of the injection device and cause defects. These are the three causes of non-defective products.

The main cause of this is the viscosity of the molten resin, and the viscosity of the molten resin greatly contributes to the quick movement of the check ring 5. In other words, if the viscosity of the molten resin is high, during injection; The molten resin stored in the space in front of the screw pet 3 is filled into the movability of the mold via the runner from the nozzle at the tip of the injection device (not shown) as the screw head 2 moves forward. , a large flow resistance occurs when passing from the space in front of the screw pet 3 to the nozzle opening at the tip of the injection device.As a result, this also spreads to the screw body 2 side, inducing quick movement of the check ring 5. ing.

On the other hand, if the viscosity of the molten resin is low, the molten resin stored in front of the screw head 3 during injection will be injected when the cavity is filled with the molten resin as the screw body 2 moves forward. The flow resistance when passing through the nozzle opening at the tip of the device is small, and the molten resin is easily filled into the cavity. For this reason, the pressure of the bath melt resin in the space in front of the screw head 3 is difficult to rise, which also reduces the back pressure acting on the screw body 2 side.

Therefore, if the viscosity of the molten resin is low, the operation of the check ring 5 will be slow, making it difficult to measure the molten resin in the bath.

As a means to eliminate these inconveniences, check ring 5
Is there a way to reduce the fitting gap between the outer circumferential surface of the heating cylinder 1 and the inner circumferential surface of the heating cylinder 1, or to reduce the operating stroke of the check ring 5? There is a limit because the resin flow path becomes narrow and the metering time increases due to increased flow resistance.

These methods naturally have their limits, and there is a desire for a method of forcibly and quickly pressing the check ring 5 against the screw front surface 12 to stop the flow of molten resin. There is a valve disclosed in Japanese Patent No. 50-140979, which has a structure in which a valve rod fitted inside a screw head is forcibly operated by electromagnetic force.

Although this is reliable as a backflow prevention operation,
It is not uncommon for the temperature inside the heating cylinder to exceed 300°C, and the heat resistance temperature of an electromagnetic coil is generally around 120°C. Therefore, implementing this technology requires special heat insulation treatment and requires a particularly small size. An electromagnetic coil is required,
Furthermore, since the electromagnetic coil is located inside the screw and rotates integrally with the screw, wiring is troublesome, making it difficult to realize and practical. There wasn't.

[Means for Solving the Problems 1] In order to solve such problems, the inner circumferential surface of the check bow ring and the assembly are engaged between the shafts via an engaging member, and the check ring For assembly, a molten resin flow hole is arranged between the inner circumferential surface and the outer circumferential surface of the shaft, and a permanent magnet is placed in the direction of the axis of the screw, facing the rear area of the non-magnetic check ring and the front area of the screw body. At the same time, the N poles and S poles were arranged in a spaced manner so as to be alternately located in each circumferential direction.

[Function] During metering (normal rotation), the reverse ring is pressed against the rear end face of the screw by the high resin pressure from the screw body, and the check ring is arranged in the rear area and the front area of the screw. The permanent magnet generates the same magnetism and maintains that state, and when the measurement of the molten resin is completed and injection starts,
At the same time as the rotation of the screw body stops, the pressure gradient between the screw body side and the space side at the front of the screw head becomes smaller, the permanent magnet generates different magnetism, and the check ring is quickly (pressed) against the front part of the screw. Therefore, backflow of molten resin can be completely prevented.

[Example] Figures 1 to 5 show an example of the check ring according to the present invention, and Figure 1 is an operation diagram of the check ring at the forward limit, and Figure 1 (a) is When injection is completed, Figure 1(b) shows the time when metering starts, Figure 2 is an operation diagram of the check ring at the backward limit, and Figure 2(a) shows the state before the end of metering. ) shows the start of injection, FIG. 3 is a side view taken along the ■-■ arrow in FIG. 1(b), FIG. 4 is a side view taken along the TV-IV arrow in FIG. 1(b),
FIG. 5 shows another embodiment similar to the present invention.

In the present invention, a screw l bead is assembled via a shaft 4 to the front end of a straight bar-shaped screw body 2 which is rotatably and movably moved forward and backward within a heating cylinder 1 and has a screw flight on its circumferential surface. The screw head 3 and the screw body 2 are provided with a reverse ring 5.

The assembly connecting the inner circumferential surface of the check ring 5, the front surface 12 of the screw body, and the rear end 3a of the screw head is made between the outer circumferential surface of the shaft 4 and the molten resin flows from the screw body 2 side to the screw head when the metering is retracted. 3. Molten resin flow holes 7 are formed for the molten resin to flow and move forward.

In the present invention, the check ring 5 and the screw body 2
A fourth non-magnetic material made of stainless steel (SLIS) is used in the front end region of.

As shown in FIGS. 1 to 4, a large number of permanent magnets 18 magnetized in the axial direction of the screw body 2 are arranged in the circumferential direction at the rear end @11 of the check ring and the front end region 2a of the screw body. They are spaced apart at a constant pitch, and alternately have north and south poles arranged at the same pitch. In recent years, various types of magnets that have high coercive force even when immersed in high melting temperatures have been developed and are commercially available.

The rod-shaped permanent magnet 18 has a resin temperature of 300°C to 40°C.
A samarium-based rare earth magnet mainly made of samarium (Sm) and cobalt (CO), which has a high coercive force even at 0"C, is used. Also, the permanent magnet 18 is connected to the rear end area of the check link 5. When attached to the front end area of the screw body 2, the permanent magnet 18 may be attached by screwing, or by attaching a holding plate so that the working end of the permanent magnet 18 cannot be inserted or removed.

In this embodiment, as shown in FIG. The grooves are carved at a constant angle θ. Further, a protrusion 33 is provided on the inner circumferential surface of the reverse ring 5, and is slidably engaged with the groove 31 described above. When assembling the check ring 5, the shaft 4 is loosely fitted almost coaxially, and when assembling the check ring 5, the inner circumferential surface of the check ring 5 and the outer circumferential surface of the shaft 4 communicate with each other between the front and rear of the check ring 5. Molten resin flow holes 7 are formed.

Also, even if the check ring 5 is pressed against the head rear surface 3a due to the flow resistance of the molten resin and the retreat of the screw body 2, the rear communication from the front communication = 14 via the molten resin flow hole 7: Resin i up to 13! There are 7 of them so that 1 tract is formed.

The opening of the molten resin flow hole 7 in the rear end surface of the check link C] 1 faces the front surface 12 of the screw body over its entire area, and the rear end surface 11 of the check ring C or the front surface 1 of the screw
When it comes into contact with 2, it is completely closed.

In particular, in the present invention, from the state where the check ring 5 is pressed against the screw body 2 side and the molten resin flow hole 7 is blocked,
The state in which this blockage is released will be explained using FIG. 1. When the injection of Nagifu resin is completed, the screw 2 is at the forward limit as shown in FIG. 1(a), and as shown in FIG. ) When transitioning from the injection completion state to the metering start condition shown in FIG. Depending on the pressure P, the rear end surface 11 of the check ring or the screw body 2
It is pressed from the side toward the screw head 3 side. For this purpose, it is easy to do two steps.

Furthermore, the process from before the end of metering to the start of injection will be explained with reference to FIG.

That is, as shown in FIG. 2(a), the screw 2 is in the retraction limit state, and the state transitions from the state before the end of metering in FIG. 2(a'l) to the injection start state shown in FIG. 2(b). When the screw body 2 completes metering and suddenly stops,
The resin is no longer supplied from the screw body 2 side to the screw head 3 side, and the resin pressure in the heating cylinder 1 is rapidly equalized. At this time, the 6R force caused by the different magnetism of the permanent magnet 18 forces the reverse upward ring 5 onto the screw front surface 12.
, and the molten resin communication hole 7 is closed.

For this reason, if the check ring 5 operates slowly and unreliably, which has been a problem in the past, the amount of molten resin injected will be uneven, resulting in a short shot or overback of the product, resulting in injection failure. The present invention completely solves the problem of deteriorating the performance of the device and producing many defective products.

As mentioned above, the assembly is done by installing the shaft 41 and the shaft 31 51j,
A protrusion 33 is provided on the inner peripheral surface of the check ring 5, and a groove 3]
The protrusion 33 is engaged, and the check ring 5 is brought into contact with the rear end 3a of the screw head to remove the molten resin.
, After completing 1 in total, attach the reverse ring 5 to the front surface 12 of the screw body.
A groove 31 is formed on the inner circumferential surface of the check ring 5 as shown in FIG.
For assembly, a protrusion 33 may be provided on the outer peripheral surface of the shaft 4.

In the present invention, a case has been described in which SUS material with a non-magnetic material is used for the check ring 5 and the front part of the screw body 2, but aluminum (Aff) alloy, ceramics, or other non-magnetic material may be used. Good too.

[Effects of the Invention] As is clear from the above explanation, the inner circumferential surface of the check ring and the assembly are engaged between the shafts via an engaging member, and the inner circumferential surface of the reverse check ring and the assembly are A molten resin flow hole is arranged between the outer peripheral surface of the shaft, and a permanent magnet is arranged in the axial direction of the screw, facing the rear area of the non-magnetic check knob and the front area of the screw. N in each circumferential direction.
By arranging the poles and south poles so that they are alternately spaced apart, the non-return link acts substantially simultaneously with the completion of the metering retraction operation prior to the injection operation, so there is no backflow of molten resin. Therefore, since there is no variation in the injection amount due to backflow, it is possible to accurately inject a constant amount of molten resin, and the product yield is greatly improved.

[Brief explanation of drawings]

1 to 5 show one embodiment of the check ring according to the present invention, FIG. 1 is an operation diagram of the check ring at the forward limit, and FIG. 1(a) is at the time of completion of injection. Figure 1 (b) shows the time at the start of metering, Figure 2 is an operation diagram of the check ring at the retraction limit, Figure 2 (a) shows before the end of metering, and Figure 2 (b) shows the start of injection. Fig. 3 shows the time of Fig. 1(b) III-II.
4 shows a side view taken along arrows IV--IV of FIG. 1(b), and FIG. 5 shows another embodiment similar to the present invention. Further, FIGS. 6 and 7 show a conventional example, in which section 6 is a sectional view showing the overall structure of the injection molding machine, and FIG. 7 is a partially cutaway front view of the tip of the screw. 1... Heating cylinder, 2... Screw body, 3... Screw head, 3a... Rear end of screw head, 4... Shaft for assembly, 5- ---Reverse check lens, 7 --- Molten resin flow hole, 9 --- Front end surface of check ring, 10 --- Projection, 11 ---・Rear end surface of check ring, 12...
・Front side of the screw body, 13... Rear communication port,
14...Front communication port, 18...Permanent magnet, 31...Groove, 33...Protrusion. Patent applicant Ube Industries, Ltd. (a) At the completion of injection (a) Before the end of measurement (b) At the start of injection

Claims (1)

[Claims] The screw head is attached to the front end of the screw body, which is rotatably attached to the heating cylinder so that it can move forward and backward, and the screw head is attached to the front end of the screw head via a small diameter assembly shaft, and the screw front side of the screw body. In the check ring fitted so as to be slidable in the front-rear direction, the inner peripheral surface of the check ring and the assembly shaft are engaged with each other via an engagement member, and the inner peripheral surface of the check ring and the assembly are assembled. A molten resin flow hole is arranged between the outer peripheral surfaces of the shaft, and a permanent magnet is arranged in the axial direction of the screw, facing the rear area of the non-magnetic check ring and the front area of the screw body. A check ring for a resin molded screw, characterized in that N poles and S poles are spaced apart and arranged alternately in the circumferential direction.