JPH07329131A - Hot runner mold apparatus - Google Patents

Abstract

PURPOSE:To shorten a molding cycle without bringing about the deficiency of a product by increasing the cooling speed of the resin in the vicinity of the gate of a cavity. CONSTITUTION:The protruding part 61 opposed to the gate 21 of a fixed mold 1 is formed to the cavity forming surface 58a of the core member 58 of a movable mold 2. The wall thickness in the vicinity of the gate 21 in a product can be made sufficiently thin by the protruding part 61. Therefore, the cooling speed of the resin in the vicinity of the gate 21 can be increased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a valve gate type hot runner mold apparatus, which is used, for example, for molding an audio tape cassette half.

[0002]

2. Description of the Related Art A hot runner mold apparatus used for injection molding of a thermoplastic resin always keeps the resin from the sprue and runner to the vicinity of the gate in a molten state in order to enhance the molding efficiency. On the other hand, since the resin filled in the product-shaped cavity must be cooled and solidified, it is necessary to open and close the gate part by some means in the hot runner mold device. The gate opening / closing method includes a valve gate method in which the gate is mechanically opened / closed by a valve, and an open gate method in which the resin in the gate portion is melted or solidified by temperature control by a hot tip. In addition,
The resin filled in the cavity is cooled by passing water through a cooling water passage provided around the cavity.

FIG. 5 shows an example of a conventional valve gate type mold device. In the figure, 81 is a fixed cavity member, 82 is a movable core member, and a product-shaped cavity 83 is formed between the cavity member 81 and the core member 82 when the mold is closed. A gate bush 84 is embedded and fixed in the cavity member 81. The tip portion 85 of the gate bush 84 is slightly projected and exposed to the cavity forming surface 81a of the cavity member 81, and has a gate 86. A valve casing 87 is fitted in the gate bush 84. The valve casing 87 has a resin passage 88 inside and a valve pin 89 that moves up and down in the drawing to open and close the gate 86. A band heater 91 is provided on the outer peripheral side of the valve casing 87. On the other hand, a cooling water passage 92 is formed between the cavity member 81 and the gate bush 84. The gate 86 is formed on the cavity forming surface 82a of the core member 82.
A concave portion 93 is formed at a position facing to. This recess 93
Is intended to reduce resistance to resin flow from the gate 86 into the cavity 83. Note that there is also a conventional mold device in which the cavity forming surface facing the gate is flattened without forming such a recess.

At the time of molding, after closing the mold, the gate 86 is opened as shown by the solid line, and the cavity is opened from this gate 86.
The molten resin is poured into 83. After the resin filled in the cavity 83, that is, the product has cooled and solidified to some extent,
The valve pin 89 closes the gate 86 as shown by the dashed line. Further, after the product is sufficiently cooled and solidified, the mold is opened and the product is taken out. The above steps are repeated, but the gate
The resin in the resin passage 88 up to 86 is always kept in a molten state by the heating of the heater 91.

[0005]

By the way, in the injection molding of a thermoplastic resin, if the product molded in the cavity 83 is taken out before being sufficiently cooled, the product will be cooled with the outside of the mold. It is easily deformed and defective. Especially in the hot runner mold apparatus, since the resin passage 88 up to the vicinity of the gate 86 is kept hot, the cooling of the vicinity of the gate 86 in the cavity 83 is likely to be delayed, but the temperature of each part of the product is uneven, When the product is taken out, it is more likely to cause defects due to uneven cooling. For example, sink marks are likely to occur near the gate 86 in the product. Further, if the mold is opened while the vicinity of the gate 86 in the product is not sufficiently cooled, a defect such as so-called stringing may occur in the mark of the gate. On the other hand, if the cooling time of the product in the mold is lengthened, the molding cycle becomes longer and the productivity decreases.

Moreover, in the above-mentioned conventional mold apparatus, the gate is
Since the concave portion 93 is formed on the cavity forming surface 82a facing the 86, and the product has a considerable thickness even at the gate 86 portion, there is a problem that cooling around the gate 86 is likely to be delayed. Further, as described above, there is a mold device in which the cavity forming surface facing the gate is flat, but nevertheless, the product has a considerable thickness even at the gate portion, and cooling in the vicinity of the gate is likely to be delayed. Since the cavity member 81 side is the surface side of the product, there is a limit to how large the protrusion amount of the tip 85 of the gate bush 84 is.

The present invention is intended to solve such a problem, and provides a hot runner mold apparatus capable of quickly cooling the vicinity of the gate in the cavity and shortening the molding cycle without causing product defects. The purpose is to provide.

[0008]

In order to achieve the above-mentioned object, the present invention provides a plurality of mutually movable mold bodies which form a cavity therein when the mold is closed, and a plurality of mold bodies formed in the mold body. In a hot runner mold device, which is provided with a gate opening / closing mechanism for opening / closing a gate that opens, and which keeps resin in a resin passage communicating with the gate in the mold always in a molten state, the wall surface of the mold facing the gate A convex portion is formed on the surface.

[0009]

In the hot runner mold apparatus of the present invention, the molten resin is injected into the cavity from the gate with the mold closed and the gate opened. Then, after the resin filled in the cavity, that is, the product is cooled and solidified to some extent, the gate is closed. Further, after the product is sufficiently cooled and solidified, the mold is opened and the product is taken out. Although the above steps are repeated, the resin in the resin passage up to the gate is always kept in a molten state. At the time of the molding, since the wall surface of the mold body facing the gate has a convex portion and the product is thin at the gate portion, the resin in the vicinity of the gate in the cavity is quickly cooled.

[0010]

EXAMPLE A first example of the hot runner mold apparatus of the present invention will be described below with reference to FIGS. The hot runner mold apparatus of this embodiment is of the valve gate type. In FIG. 2, 1 is a fixed die, 2 is a movable die, and these fixed die 1 and movable die 2 which are die bodies move vertically with respect to each other to open and close, and a plurality of product shapes are formed when the die is closed. The cavity 3 is formed inside.

The fixed mold 1 includes a fixed-side mold plate 4, fixed-side receiving plates 5 and 6 attached to the back surface (upper surface in the drawing) of the fixed-side mold plate 4, and an upper surface of the fixed-side receiving plate 6. It comprises a fixed side mounting plate 8 mounted via a spacer block 7 and mounted on a fixed side platen of an injection molding machine, a manifold 9 provided between the fixed side mounting plate 8 and the fixed side receiving plate 6, and the like. There is. The fixed-side template 4 is
A plurality of cavity members 12 that respectively form the surface, that is, the outer surface of a product are embedded and fixed in a frame plate 11. A locating ring 13 is fixed to the outer surface of the fixed-side mounting plate 8, and a sprue bush 14 located on the inner peripheral side of the locating ring 13 and connected to the nozzle of the injection molding machine penetrates through the locating ring 13. The sprue 15 is fixed and the inside of this sprue bush 14 is a resin passage.
It has become. The lower end of the sprue bush 14 in the drawing is connected to the manifold 9. A runner 16 which is a resin passage communicating with the sprue 15 is formed in the manifold 9. The manifold 9 has a heater 17 built therein. Further, a plurality of gate bushes 22 each having a gate 21 opening to each cavity 3 are embedded and fixed in the cavity member 12 of the stationary mold plate 4. As shown in FIG. 1, the gate 21 is formed on the tip end portion 23 of the gate bush 22 which is slightly projected and exposed on the cavity forming surface 12a of the cavity member 12. Also, this gate bush 22
A cooling water passage 24, which is a cooling fluid passage, is formed between the cavity member 12 and the cavity member 12.
A pair of O-rings 25 and 26 are provided with the 24 in between. Further, as shown in FIG. 2, a cooling water passage 27, which is a cooling fluid passage and surrounds the cavity 3, is formed in the cavity member 12 and the like.

Further, the fixed mold 1 includes the gate 21.
A valve device 31 which is a gate opening / closing mechanism for opening and closing the is provided. Here, the configuration of the valve device 31 is mainly shown in FIG.
It will be described based on. A plurality of tubular valve casings 32 are fixed to the fixed side receiving plates 5 and 6 in a penetrating state. The lower end of the valve casing 32 shown in the drawing is
The gate bushes 22 are fitted in the respective gate bushes 22. Also,
The valve casing 32 has a flange portion 33, which contacts the lower surface of the manifold 9 in the drawing and is fixed to the fixed side receiving plate 6, in the upper portion of the drawing. On the other hand, the lower part of the outer peripheral side of the valve casing 32 is covered with a band heater 34, and the band heater 34 is covered with a cylindrical heater cover 35 from the outer peripheral side. An outer cylinder 36 is provided on the outer peripheral side. The band heater 34 is electrically connected to an external power supply circuit via a cord 37, and has a sensor 38 on the inner peripheral side. Further, in the valve casing 32, a guide bush 39 is coaxially fitted and fixed in the upper portion of the drawing, and a valve pin holder 40 is fitted in the lower portion of the drawing. This valve pin holder 40
Is fixed from below by a tubular pressing member 41 screwed into the lower portion of the valve casing 32. The final branch passage of the runner 16 of the manifold 8 communicates with the gate 21 through the valve casing 32 and the resin passage 42 in the retainer 41. Then, each of the valve casings 32
A valve pin 43 is supported therein so as to be movable in the vertical direction in the figure, that is, in the axial direction. The valve pins 43 are slidably pierced and supported in the guide bush 39 and the valve pin holder 40. Also, each valve pin 43
Are pierced through a through hole 44 formed in the manifold 9 in the vertical direction in the drawing and are respectively connected to a plurality of hydraulic cylinder devices 45 (illustrated in FIG. 2) provided on the fixed side mounting plate 8. It is driven by the device 45. The lower end of the valve pin 43 in the drawing is removably fitted into the gate 21 to close the gate 21.

On the other hand, as shown in FIG.
Is a movable side template 51, a movable side receiving board 52 attached to the back surface (lower surface in the drawing) of the movable side template 51, and a spacer block 53 attached to the lower surface of the movable side receiving board 52 via a spacer block 53 for injection. It comprises a movable side mounting plate 54 which is mounted on the movable side platen of the molding machine. Along with this, between the movable side mounting plate 54 and the movable side receiving plate 52, there is provided a projecting plate 55 which moves up and down relative to these, and the projecting pin 56 is mounted on the projecting plate 55. Is fixed. These protruding pins 56 are provided on the movable side receiving plate 52.
Further, the movable side mold plate 51 is slidably penetrated and the tip is positioned so as to face the cavity 3. The movable side mold plate 51 is a frame plate 57 in which a plurality of core members 58 respectively forming the back surface, that is, the inner surface of the product are embedded and fixed. Further, in the core member 58 or the like, a cooling water passage 59, which is a cooling fluid passage that surrounds the cavity 3, is formed.

Then, as shown in FIG. 1, the core member is
The gate 2 is formed on the cavity forming surface (wall surface) 58a of 58.
A spherical convex portion 61 is integrally formed at a position opposed to 1.

Next, the operation of the above configuration will be described. At the time of molding, the fixed mold 1 and the movable mold 2 are closed, and as shown by the solid line in FIG. 1, the valve pin 43 is raised by the cylinder device 45 to open the gate 21 from the nozzle of the injection molding machine. Inject the molten resin. This resin is from sprue 15 to runner 16 of manifold 9.
And through the valve casing 32 and into the cavity 3 from the opened gate 21. After that, when the resin filled in the cavity 3 is cooled and solidified to some extent, the valve pins 43 are lowered by the cylinder device 45 and the valve pins 43 are fitted into the gates 21 to close the gates 21. Further, after the resin filled in the cavity 3, that is, the product is sufficiently cooled and solidified, the fixed mold 1 and the movable mold 2 are opened, and the product is taken out. At this time, the ejection pin 56 ejects the product to release it.

While the above molding operation is repeated, the heating of the heater 17 during that time causes the manifold 9 to be heated.
The resin in the runner 16 is always kept in a molten state, and the resin in the resin passage 42 of the valve casing 32 is always kept in a molten state by heating the heater 34. On the other hand, the resin in the cavity 3 is positively cooled by the water passing through the cooling water passages 24, 27 and 59 surrounding the cavity 3. The cooling fluid is not limited to water, but oil or the like may be used.

At the time of molding as described above, since the protrusion 61 is provided on the cavity forming surface 58a of the core member 58 at a position facing the gate 21, the tip end portion of the gate bush 22 protruding from the cavity forming surface 12a of the cavity member 12 is formed. Together with 23, the product at the gate 21 can be made sufficiently thin. Therefore, the resin in the vicinity of the gate 21 in the cavity 3 can be quickly cooled. As a result, the molding cycle can be shortened without causing defects such as sink marks in the vicinity of the gate 21 in the product.

FIG. 3 shows a second embodiment of the present invention. The parts corresponding to those in the first embodiment are designated by the same reference numerals, and the description thereof will be omitted. The same applies to the third embodiment described later. In the second embodiment, the gate bush 22 is not exposed on the cavity forming surface 12a of the cavity member 12 and the gate 66 is formed on the cavity member 12 itself.
Then, near the gate 66, the cavity forming surface
12a is flat. On the other hand, a convex portion 67 is also integrally formed at a position facing the gate 66 on the cavity forming surface 58a of the core member 58, and the convex portion 67 has a truncated cone shape. The function and effect are similar to those of the first embodiment.

FIG. 4 shows a third embodiment of the present invention.
In the third embodiment, the protrusion pin 71 for releasing the molded product from the mold is used to form the convex portion facing the gate 21. That is, the cylindrical protruding pin 71
Is located opposite to the gate 21, and even in the mold closed state,
The tip portion 72 slightly projects from the cavity forming surface 58a of the core member 58 to the fixed mold 1 side. That is, the tip portion 72 of the protrusion pin 71 becomes a convex portion. The function and effect are similar to those of the first embodiment, but the protrusions 71 are used to form the protrusions, so that the core member 58 can be easily processed in manufacturing the mold.

The present invention is not limited to the above embodiment, and various modifications can be made. For example,
The shape of the convex portion formed on the movable cavity forming surface facing the gate is not limited to the spherical shape, the truncated cone shape, and the cylindrical shape.
Various types such as a pyramid shape, a truncated pyramid shape, or a conical shape are possible. Further, in the mold apparatus of the above-described embodiment, the gate opening / closing mechanism is a valve device that mechanically opens / closes the gate, but the gate opening / closing mechanism melts or solidifies the resin in the gate portion by controlling the temperature by the hot tip. It may be an open gate type or the like.

[0021]

According to the present invention, in the hot runner mold apparatus, since the convex portion is formed on the wall surface of the mold body facing the gate, the molded product can be made sufficiently thin at the gate portion. As a result, the resin in the vicinity of the gate in the cavity can be cooled quickly, so that the molding cycle can be shortened without causing defects in the product.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view showing a first embodiment of a hot runner mold device of the present invention.

FIG. 2 is a sectional view of the same as above.

FIG. 3 is a sectional view showing a second embodiment of the hot runner die apparatus of the present invention.

FIG. 4 is a sectional view showing a third embodiment of the hot runner die apparatus of the present invention.

FIG. 5 is a cross-sectional view showing an example of a conventional hot runner mold device.

[Explanation of symbols]

 1 Fixed type (mold body) 2 Movable type (mold body) 3 Cavity 15 Sprue (resin passage) 16 Runner (resin passage) 21 Gate 31 Valve device (gate opening / closing mechanism) 42 Resin passage 61 Convex portion 66 Gate 67 Convex portion 72 Tip of protruding pin (projection)

Claims (1)

[Claims] 1. A mold body comprising: a plurality of mutually movable mold bodies that form a cavity therein when the mold is closed; and a gate opening / closing mechanism that opens and closes a gate formed in the mold body and opening to the cavity. In the hot runner mold device, which is provided in the mold and always keeps the resin in the resin passage communicating with the gate in a molten state, the hot runner mold device is characterized in that a convex portion is formed on the wall surface of the mold body facing the gate. .