JP2861365B2 - Screws for resin molding - Google Patents

Description

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

[Prior Art] FIG. 9 is a longitudinal sectional view of a main part of a most common conventional check ring.

In FIG. 9, the check ring is a small-diameter assembling shaft 4 having a screw head 3 fixed to the front end of the screw body 2.
A cylindrical check ring 5 that is loosely fitted into the heating cylinder 1 so that the outer diameter thereof can prevent leakage of the molten resin between the heating cylinder 1 and the heating cylinder 1 is slidably fitted in the front-rear direction. A direct communication path 7 is provided between the inner peripheral surface of the check ring 5 and the peripheral surface of the mounting shaft 4 so that the molten resin can flow from the screw body 2 side to the front of the screw head 3. doing.

The front end face 9 of the check ring has a projecting portion 10 at a predetermined interval.
Are provided, so that a resin passage extending from the front communication port 14 to the rear communication port 13 via the communication path 7 even when the check ring 5 is pressed against the screw head 3 is formed.

The opening of the communication passage 7 in the rear end face 11 of the check ring is entirely opposed to the front face 12 of the screw body, and when the rear end face 11 of the check ring abuts on the screw front face 12, it is completely closed. Is to be closed.

At the time of retraction of the plasticized measurement of the molten resin (hereinafter, simply referred to as the time of retraction), the check ring 5 is pressed forward by the flow resistance of the molten resin, and the rear communication port 13, the communication path 7, and the front communication port. It is pushed through 14 to the front of the screw head 3.

At the time of injection, the screw body 2 and the screw head 3 move forward integrally, while only the check ring 5 remains and closes the rear communication port 13 to prevent the backflow of the molten resin.

[Problems to be Solved by the Invention] Generally, the non-return ring 5 smoothly moves the molten resin when the screw body 2 is rotated and retracted to extrude the molten resin forward of the screw head 3 during measurement. Although it is necessary to pass the molten resin, it is required to prevent the backflow of the molten resin at the time of injection.

If the operation of the check ring 5 is slow and uncertain, the amount of molten resin to be injected becomes non-uniform. It is the main cause of non-defective products.

The main cause is the viscosity of the molten resin, and the magnitude of the viscosity of the molten resin greatly contributes to the quick operation of the check ring 5. That is, when the viscosity of the molten resin is large, at the time of injection, the molten resin stored in the space in front of the screw head 3 passes through the runner from the nozzle opening at the tip of the injection device (not shown) as the screw body 2 advances. When filling into the cavity of the mold, large flow resistance is generated when passing from the front space of the screw head 3 to the nozzle opening at the tip of the injection device. As a result, it spreads to the screw main body 2 side, and the quick operation of the check ring 5 is induced.

Conversely, if the viscosity of the molten resin is low, the molten resin stored in front of the screw head 3 will be injected when the molten resin is filled into the cavity as the screw body 2 advances, during injection. The flow resistance when passing through the nozzle port at the tip of the device is small, and the molten resin is easily filled into the cavity. For this reason, the molten resin pressure in the space in front of the screw head 3 is unlikely to rise, which also reduces the back pressure acting on the screw body 2 side.

Therefore, if the viscosity of the molten resin is small, the check ring 5
Is slow, and the measurement of the molten resin tends to be uneven.

Means for eliminating these inconveniences include reducing the clearance between the outer peripheral surface of the check ring 5 and the inner peripheral surface of the heating cylinder 1 and reducing the operation stroke of the check ring 5. However, the former has a limit due to the occurrence of galling, and the latter has a limit due to an increase in measuring time due to an increase in flow resistance due to a narrow resin flow path.

These methods have their own limitations, and there is a demand for a method in which the check ring 5 is forcibly and quickly pressed against the screw front surface 12 to stop the flow of the molten resin. Japanese Patent Laid-Open Publication No. Sho 50-140979 discloses a structure in which a valve stem fitted inside a screw head is forcibly operated by electromagnetic force.

Although this is reliable as an operation to prevent backflow, the temperature inside the heating cylinder is rarely over 300 ° C, and the heat-resistant temperature of the electromagnetic coil is generally around 120 ° C. This requires a special thermal insulation treatment and a particularly small electromagnetic coil.
Furthermore, since the electromagnetic coil is inside the screw and rotates integrally with the screw, the wiring becomes troublesome and lacks practicality and practicality, and cannot be an essential solution.

[Means for Solving the Problems] In order to solve such a problem, a plurality of permanent magnets are provided at a rear end area of the check ring made of a non-magnetic material and a front end area of the screw body made of a non-magnetic material. Are arranged in the axial direction of the screw main body, and are arranged so as to be spaced apart such that N poles and S poles are alternately located in each circumferential direction.

[Operation] Permanent magnets are arranged in the axial direction of the screw so as to face the rear area of the check ring and the front area of the screw, and are arranged so that N poles and S poles are alternately located in each circumferential direction. With
A convex claw is provided at the front end of the check ring, and is engaged with a recess formed at the rear of the screw head. by this,
During weighing (forward rotation), the check ring rotates together with the screw body, and the permanent magnets arranged in the rear area of the check ring and the screw front area generate the same magnetism. When the injection of the molten resin is completed after the molten resin has been measured and the injection is started, the permanent magnet generates heteromagnetism at the same time as the rotation of the screw body is stopped, and the check ring is quickly pressed against the screw front. Therefore, the backflow of the molten resin can be completely prevented.

1 to 8 show an embodiment of a check ring according to the present invention. FIG. 1 is a front view of a main part at the time of measurement, and FIG. 2 is an arrow II-II in FIG. FIG. 3 is a front view of a main part when weighing is completed, FIG. 4 is a partially cut front view taken along arrow IV-IV of FIG. 3, and FIG. 5 is VV of FIG. FIG. 6 is a side view taken along the line VI-VI in FIG. 1, FIG. 7 is an operation view showing release from the operation of the check ring, and FIG. 8 is a view showing the start of injection from the end of metering. FIG.

According to the present invention, a screw head 3 is mounted on a front end of a straight rod-shaped screw main body 2 provided with a screw flight on a peripheral surface which is rotatably mounted in a heating cylinder 1 and capable of moving forward and backward. A check ring 5 is provided between the screw head 3 and the screw main body 2.

Between the inner peripheral surface of the check ring 5 and the outer peripheral surface of the assembling shaft 4 connecting the screw body front surface 12 and the screw head rear end 3a,
A communication passage 7 is formed for the molten resin to flow from the screw body 1 to the front of the screw head 3 and move when the measurement is retracted.

In the present invention, a non-magnetic material of stainless steel (SUS) is used for the front end regions of the check ring 5 and the screw body 2.

In the rear end area of the check ring and the front end area of the screw body, as shown in FIGS. 1 to 4, a plurality of permanent magnets 18 magnetized in the axial direction of the screw body 2 have a constant pitch in the circumferential direction. They are spaced apart from each other, and are alternately arranged at the same pitch with N poles and S poles. In recent years, various types having a high coercive force even when a magnet is immersed in a high-temperature molten resin have been developed and marketed.

As the rod-shaped permanent magnet 18, a samarium-based rare earth magnet mainly composed of samarium (Sm) and cobalt (Co) having a high coercive force even at a molten resin temperature of 300 ° C to 400 ° C is used. Further, the permanent magnet 18 is screwed in when it is attached to the rear end area of the check ring 5 and the front end area of the screw body 2, but the working end of the permanent magnet 18 cannot be inserted or pulled out by attaching a holding plate. May be.

On both sides of the front end face 9 of the check ring, a pair of convex claws 17 are provided. 5 permanent magnets arranged in the circumferential direction of the rear end area and the front end area of the screw body 2
A claw engaging portion 19 having a groove width obtained by adding the width of the protruding claw 17 to the length of one pitch of 18 is engraved. It is slidably engaged left and right.

On the front end face 9 of the check ring, a pair of the above-mentioned convex nails is provided.
Apart from 17, several projecting portions 10 are provided at predetermined intervals, and when the check ring 5 is pressed against the screw head 3, the check ring 5 is moved from the front communication port 14 to the rear communication port 13 through the communication path 7. A resin passage leading to is formed.

The opening of the communication passage 7 in the rear end face 11 of the check ring is entirely opposed to the front face 12 of the screw body, and when the rear end face 11 of the check ring abuts on the screw front face 12, it is completely closed. Is to be closed.

Particularly, in the present invention, a state in which the check ring 5 is pressed against the screw body 2 side and the communication passage 7 is closed from the state where the communication path 7 is closed will be described with reference to FIG. When the injection of the resin is completed, as shown in FIG. 7 (a), the screw 2 is in the state of the forward limit, and FIG.
In the case of shifting from the injection completion state to the measurement start state shown in FIG. 7 (b), as shown in FIG.
When the screw body 2 rapidly starts rotating from a state in which the screw body 2 comes into contact with the right end side 20 of the claw engaging portion, the measurement of the molten resin is started, and the molten resin between the screw head rear end 3a and the check ring front end 9 is formed. The pressure P acts on the projected area A on the right end side 20 of the claw engaging portion, and the check ring 5 is relatively moved relative to the screw head 2 in a direction opposite to the rotation direction of the screw 2 by P (Kg / cm ² ) × A (cm
² ) Pressed with a force of = F (Kg).

(2) Further, at the time when the screw body 2 starts retreating while rotating with the start of the measurement, as shown in FIG. 7 (b), the resin pressure on the screw body 2 side with the check ring 5 as the boundary. Is greater than the resin pressure on the screw head 3 side, so that the check ring 5 is pushed from the screw body 2 side to the screw head 3 side.

By the synergistic action of (1) and (2) described above, the closing of the molten resin passage by the check ring 5 at the time of transition from the completion of injection to the start of measurement and at the time of transition from the completion of measurement to the start of injection can be performed smoothly.

Further, if the operation of the check ring 5, which has been a problem in the past, is slow and uncertain, the amount of molten resin to be injected becomes non-uniform. The fact that the present invention has completely solved the problem that the performance of the above has been reduced and many defective products have occurred has been described with reference to FIG.

That is, when the measurement of the molten resin is completed, FIG.
As shown in the figure, the screw 2 is in the retracted state,
When shifting from the state before the end of the measurement in FIG. 8 (a) to the injection start state shown in FIG. 8 (b), the convex pawl 17 as shown in FIG. When the screw main body 2 completes the measurement and stops suddenly from the state in which it comes into contact with the non-return ring 5a due to the magnetic force of the permanent magnet 18 due to the different magnetism.
Is drawn to the screw front surface 12, and the communication port 7 is closed.

In the present invention, the case where a SUS material having a non-magnetic material is used in the front portion of the check ring 5 and the screw body 2 has been described. However, the use of an aluminum (Al) alloy, ceramics, and other non-magnetic materials has been described. Is also good.

Further, in the present invention, the permanent magnets 18 are arranged at the rear end area of the check ring 5 and the front end area of the screw 2, but are arranged at the front end area of the check ring 5 and the rear end area of the screw head 3. A configuration may be adopted.

[Effects of the Invention] As is clear from the above description, a plurality of permanent magnets are provided at the rear end area of the check ring made of a non-magnetic material and at the front end area of the screw body made of a non-magnetic material. The check ring substantially completes the metering retraction operation prior to the injection operation by arranging the check ring in such a manner that the N-pole and the S-pole are alternately arranged in each circumferential direction. At the same time, there is no backflow of the molten resin, and therefore, there is no variation in the injection amount due to the backflow, so that a fixed amount of the molten resin can be accurately injected, and the product yield is greatly improved.

[Brief description of the drawings]

1 to 8 show an embodiment of a check ring according to the present invention. FIG. 1 is a front view of a main part at the time of weighing, and FIG.
FIG. 3 is a partially cutaway front view taken along the line II-II of FIG. 3, FIG. 3 is a front view of the main part at the time of completion of weighing, FIG. FIG. 1 is a side view taken along the line V-V of FIG. 1, and FIG.
FIG. 7 is an operation view showing release from operation of the check ring, FIG. 8 is an operation view showing the start of injection from the end of metering, and FIG. 9 is a conventional check. FIG. 2 shows a vertical sectional view of a main part of a ring. 1 ... heating cylinder, 2 ... screw body, 3 ... screw head, 3a ... rear end of screw head, 4 ... assembly shaft, 5 ... check ring, 7 ... communication passage, 9 ... ... front end face of check ring, 10 ... protruding part, 11 ... rear end face of check ring, 12 ... screw front face, 13 ... rear communication port, 14 ... front communication port, 17 ... convex Claw, 18: permanent magnet, 19: claw engaging part, 20: right end of claw engaging part, 20a: left end of claw engaging part.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-1-272430 (JP, A) JP-A-60-171119 (JP, A) JP-A-60-142918 (JP, U) (58) Field (Int.Cl. ⁶ , DB name) B29C 45/45-45/84

Claims (1)

(57) [Claims] A screw head is mounted on a front end surface of a screw body rotatably mounted in a heating cylinder and capable of moving forward and backward through a small-diameter mounting shaft. A check ring having a convex claw engaged with a concave groove formed in the circumferential portion is slidably fitted in a front-rear direction between a rear end surface of the screw head and a front end surface of the screw body. In the mounted resin molding screw, a plurality of permanent magnets are disposed in the axial direction of the screw main body in a rear end area of the check ring made of a non-magnetic substance and a front end area of the screw main body made of a non-magnetic substance. In addition, a resin molding screw is characterized in that N-poles and S-poles are arranged so as to be alternately arranged in each circumferential direction.