JP2002292692A - Injection mold - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an injection mold easy in the maintenance of a gas venting device. SOLUTION: The injection mold is equipped with a piece for forming at least a part of a mold cavity, a gas venting means for venting the gas generated when a molten polymeric raw material is injected in the mold cavity, and a holding means for holding the gas venting means from the direction crossing the mounting direction of the gas venting means at a right angle. The gas venting means is formed into the piece coming into contact with the parting line of the mold and, concretely, the opening part into the mold cavity is closed by a porous metal plate and a groove, in which the locking projected part of the holding member for constituting the holding means is fitted, is formed at least to the outer peripheral side surface opposed to the holding means.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mold for injection molding, and more particularly, to a method of filling a mold with air and molten polymer material when the molten polymer material is injected into the mold. The present invention relates to an injection mold that includes a gas release device that can efficiently discharge generated gas to the outside, and that can easily be attached and detached.

[0002]

2. Description of the Related Art In general, in injection molding, a heated and compressed molten polymer material is filled into a mold cavity at high pressure,
It consists of a process of holding and cooling in a mold and then removing it.

[0003] In this series of processes, when a high-pressure molten polymer material is filled into a mold cavity, the molten polymer material is generated at the end of the resin flow or at a portion where the branched molten polymer material joins. The gas which accumulates becomes hot due to adiabatic compression at the end of the flow of the resin, resulting in molding defects called weld lines and appearance defects called burning on the surface of the molded product.

[0004] Since the molten polymer raw material itself is in response to a cost reduction request from a production plant, the amount of gas generated from the molten polymer raw material tends to increase, so that for a mold or a molding machine, It tends to be even worse.

[0005] Usually, as a method of degassing a mold for injection molding, a depth of 0.02 to 0.0
A slit of about 3 mm is inserted, and a gas is discharged from the portion to the outside of the mold. A porous chamber metal is buried in a flow end portion or a portion where a branched molten polymer material joins,
A method of discharging gas from the piece to the outside of the mold and a method of using an ejector pin are employed.

The method using the ejector pin includes:
By the slope provided at the tip of the ejector pin, a gas vent groove is formed in the direction opposite to the resin filling direction,
Until the resin reaches the ejector pin, gas is exhausted through the gas vent groove.When the resin reaches the ejector pin, the ejector pin is lowered by the flow pressure of the resin to close the gas vent groove. As an improved method, as disclosed in JP-A-8-39626, a member in which a gas venting device is formed in a female screw hole provided in a deep wall surface of an insertion hole communicating with a gas venting path provided in a mold body. An “injection mold” has been proposed in which one end is fixed in a male screw shape and maintenance is taken into consideration.

[0007]

However, although the amount of gas generated from the molten polymer raw material tends to increase, the depth at which it is installed on the parting surface of the mold is 0.02 to 0.03.
In the method of discharging gas from a slit groove of about mm or a metal in a porous chamber, gas accumulated inside a mold during high-speed injection molding cannot be discharged efficiently in a short time.

[0008] Further, in the degassing method using the ejector pin, it is necessary to install the ejector pin in the degassing portion, and there is a problem that the installation causes a concave surface on the product surface. In addition, in these degassing methods, since the insert is press-fitted into the insertion hole, if the insert is attached to the mold once, it is impossible to remove the insert again. Therefore, even if the gas is solidified in the small holes or dust is clogged up during repeated molding and maintenance is required, maintenance cannot be performed easily and the gas release effect is significantly reduced. Was caused.

The above-mentioned Japanese Patent Application Laid-Open No. H8-3 taking maintenance into consideration
In the prior art method disclosed in Japanese Patent No. 9626, a groove such as a screwdriver hole for fixing to the surface of a degassing portion is transferred to a molded product. Cannot be used, which causes a problem that the range of use is restricted.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems of the prior art and to provide an injection shaping mold in which maintenance of a degassing device is easy.

[0011]

In order to achieve the above object, an injection mold according to the present invention comprises a piece forming at least a part of a mold cavity, and a molten polymer raw material in the mold cavity. And a holding means for holding the gas removing means from a direction perpendicular to the mounting direction of the gas removing means.

In the injection molding die of the present invention, the degassing means may be formed in a die in contact with a parting line of the die, or may be mounted in a direction in which the die is opened and closed. And may be formed on the piece.

Further, the injection mold according to the present invention may have a structure in which the degassing means has an opening into the mold cavity closed with a porous metal plate. A structure may be used in which a groove is formed on an outer peripheral side surface facing the holding means, into which an engaging protrusion of a holding member constituting the holding means is fitted. The cross-sectional shape may be a trapezoid.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view of an injection molding die as an embodiment, and FIG. 2 is an enlarged cross-sectional view of a portion surrounded by a circle II in FIG.

In FIG. 1, reference numeral 1 denotes a fixed-side mounting plate that holds a fixed-side template 2, and 3 denotes a fixed-side core (fixed piece) that is held by the template 2. A mold is configured. Reference numeral 15 denotes a gate portion, which is formed by attaching the spool bush 8 through the mounting plate 1 and the template 2, and passing through the inside thereof, as shown in FIG.
A molten resin as a molten polymer material is injected and injected at a high pressure from above.

Reference numeral 4 denotes a movable-side mounting plate on which the movable-side mold plate 5 is held. Reference numeral 6 denotes a movable-side core (movable piece) held by the mold plate 5, and these constitute a movable-side mold. Have been. Reference numeral 7 denotes a spacer block interposed between the mounting plate 4 and the template 5. Reference numeral 9 denotes an ejector pin attached to upper and lower ejector plates 23 and 24.

An injection molding cavity 10 is formed between the fixed piece 3 and the movable piece 6. Degassing devices 40 and 50 as degassing means are provided to the movable piece 6 and the fixed piece 3 in the vicinity of the cavity 10 where the molten resin branched in the cavity 10 merges or near the molten resin flow end. Are provided. In addition, P.
L. Indicates a parting line.

Here, a series of injection molding steps will be briefly described with reference to FIG. Before being used for molding, the resin pellets as the polymer raw material are dried in advance in the material dryer by heating a heater in a material dryer (not shown). Thereafter, the resin pellets are supplied from the inside of the material dryer to the hopper 31 on the molding machine, and are melted in the heating cylinder 32 by heating of the heater.

The molten resin retreats (to the right in the figure) by reverse rotation of the screw 33, and is kneaded and weighed. Thereafter, by the forward rotation of the screw 33, the molten resin advances (to the left in the figure), is injected into the mold, and is filled into the injection molding cavity 10 between the fixed piece 3 and the movable piece 6. You.

After cooling for a predetermined time, the movable mold 36 moves to the left in the figure together with the molded product, and thereafter the molded product is separated from the movable mold 36 by the ejector pins 9. again,
The movable mold 36 moves to the right in the figure, merges with the fixed mold 35, and repeats the kneading, weighing, pouring, and filling operations.

Returning to FIG. 2, the degassing device of the present invention will be described. The degassing device according to the present invention enables the degassing device to be attached to and detached from the mold for maintenance in the opening and closing direction of the mold, and to fix and hold the degassing device in a direction perpendicular to the mold opening and closing direction. The feature is that it can be performed. With this configuration,
The cavity surface of the degassing device can be formed smoothly, without affecting the shape of the molded product, and the degassing device can be easily attached and detached.

In the injection mold according to the embodiment, a gas venting device for releasing gas such as gas generated when the cavity 10 is filled is fixed in order to increase the gas venting effect. It is preferable that the mold is provided in a mold near a portion where the branched molten resin in the cavity 10 between the piece 3 and the movable piece 6 joins or a molten resin flowing end portion. As this degassing device, for example, a commercially available device such as a sintered vent manufactured by MISUMI Corporation or a porous metal manufactured by Kubota Corporation is used. This kind of porous metal is
Since it can be formed flush with the surface on which the cavity 10 is formed without forming irregularities transferred to the molded article, it is suitable for a gas venting device. The degassing device may have a small hole, or may degas from a gap using the force of a spring such as a degassing pin.

At an appropriate position of the movable piece 6 constituting the mold, for example, at a position corresponding to the vicinity of the portion where the molten resin joins,
A fitting hole 27 for mounting the degassing device 40 in the mold opening and closing direction is formed. The movable piece 6 has a mounting hole 25 which constitutes a holding means for holding the gas release device 40 in a direction perpendicular to the fitting hole 27, that is, in a direction perpendicular to the mold opening and closing direction. It is formed to penetrate toward the portion 61. Further, the movable piece 6 is provided with the fitting hole 27.
Subsequently, an exhaust port 26 is formed as a gas venting means penetrating into the movable piece bottom wall 62.

The mounting hole 25 is provided with the degassing device 4.
A holding member 28 that constitutes holding means for holding 0 is provided. The holding member 28 is formed with an engagement projection 29 that fits into a groove 43 formed in a gas release device 40 described later.

The degassing device 40 includes an opening 41 which is open to the cavity 10 side of the movable piece 6, a porous metal plate 42 which is press-fitted into the opening 41 and closely fixed thereto, and the holding member 28.
An annular groove 43 formed so as to be held and fixed at a predetermined position in the fitting hole 27, and an exhaust port 44 serving as a gas venting means for allowing gas to escape out of the mold. The opening portion 41 of the upper surface 45 of the degassing device 40 is closed by tightly fixing the porous metal plate 42, and the entire upper surface 45 is formed flush. Further, the exhaust port 44 is provided in the exhaust hole 2 formed in the movable piece 6.
The gas is discharged to the outside of the mold through the passage 21 through an exhaust passage 21 serving as a closed gas releasing means in the mold through the passage 6. In the present embodiment, the degassing device is configured to be attached to the movable piece as described above, but the present invention is not limited to this. It may be provided in any part of the mold facing the cavity 10 in the vicinity of the resin flow end or the like.

The mounting of the degassing device 40 on the movable piece 6 is performed as follows. First, the porous metal plate 4 is
2 is press-fitted and tightly fixed, and the degassing device 40 is fitted into the fitting hole 27 formed in the movable piece 6. Subsequently, the engaging projection 29 of the holding member 28 inserted from the mounting hole 25 moves forward (moves rightward in the drawing), and is fitted into the annular groove 43 of the degassing device 40. As a result, the degassing device 40 is positioned so as to be flush with the movable piece 6 along (partly in contact with) the parting line as shown in the figure, and is fixed and held at that position.

Contrary to the mounting described above, the degassing device 40 is detached from the movable piece 6 as follows. First, the holding member 28 is retracted in the mounting hole 25 by using a dedicated jig (not shown) or the like, and the engaging projection 29 is pulled out from the annular groove 43, and the engagement between the degassing device 40 and the holding device 28 is performed. Release the state. Thereafter, a special jig or the like is inserted into the degassing device 40 from the exhaust hole 26 side, and the degassing device 4 is inserted.
0 may be pushed out of the fitting hole 27.

The holding member 28 has a circular or square cross section, and may be advanced / retracted in the mounting hole 25 by a dedicated jig or the like, or may be provided with a screw mechanism having a circular cross section to advance / retreat. You may do so. Further, the cross-sectional shape of the annular groove 43 of the engagement protrusion 29 may be square as shown in FIG. 2, or may be a trapezoid that tapers toward the bottom of the annular groove 43. The mounting hole 25 and the holding member 28
It is preferable to apply a sealing member such as an O-ring or the like so as not to allow gas to escape.

The degassing device 50 has the same shape as the degassing device 40 described above, and a description thereof will be omitted.

In the present embodiment, the case where two gas venting devices are provided is disclosed. However, the number is not limited to this, and any number of gas venting devices may be provided.

[0031]

As described above, in the injection mold of the present invention, the degassing device is detachable in the mold opening / closing direction, and the degassing device is held and fixed from the side of the piece. Since it is configured, it is easy to attach and detach, and no irregularities are formed on the molded product. Further, when the gas venting device is clogged, the gas venting device can be easily replaced to remove the clogging, maintenance is easy, and the gas venting state can always be maintained in good condition. Therefore, product yield and productivity can be improved.

[Brief description of the drawings]

FIG. 1 is a sectional view of an injection mold provided with a degassing device of the present invention.

FIG. 2 is an enlarged sectional view of the degassing device in FIG.

FIG. 3 is a schematic view of an injection molding apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fixed-side mounting plate 2 Fixed-side mold plate 3 Fixed-side core (piece) 4 Movable-side mounting plate 5 Movable-side mold plate 6 Movable-side core (piece) 7 Spacer block 8 Spool bush 9 Ejector pin 10 Cavity 15 Gate part 19, Reference Signs List 21 Exhaust passage 23, 24 Ejector plate 25 Mounting hole 26 Exhaust hole 27 Fitting hole 28 Holding member 29 Engagement projection 31 Hopper 32 Heating cylinder 33 Screw 34 Injection cylinder 35 Fixed mold 36 Movable mold 40, 50 Gas Punching device 41 Opening 42 Porous metal plate 43 Annular groove 44 Exhaust port 45 (Gas removing device) Top surface 61 (Movable piece) Side wall 62 (Movable piece) Bottom wall L. Parting line

Claims (7)

[Claims] 1. A piece forming at least a part of a mold cavity, a gas releasing means for discharging gas generated when a molten polymer material is injected into the mold cavity, and mounting of the gas releasing means. And a holding means for holding the gas venting means from a direction perpendicular to the direction. 2. The injection molding die according to claim 1, wherein said degassing means is formed in a die contacting a parting line of said die. 3. The gas venting means is mounted in a direction in which the mold is opened and closed.
The mold for injection molding according to 1. 4. The injection molding die according to claim 1, wherein said degassing means is formed on said piece. 5. The injection molding apparatus according to claim 1, wherein said gas venting means has an opening into said mold cavity closed by a porous metal plate. Mold. 6. The gas venting means is characterized in that at least an outer peripheral surface facing the holding means is formed with a groove into which an engaging projection of a holding member constituting the holding means is fitted. Item 6. The injection mold according to any one of Items 1 to 5. 7. The injection mold according to claim 6, wherein the engaging protrusion and the groove have a trapezoidal cross section.