JP2957879B2 - Injection mold - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection mold,
In particular, it relates to a method of sealing a cooling medium passage of a mold.

[0002]

2. Description of the Related Art In an injection molding die of a thermoplastic resin, after injection of a molten resin, cooling is performed by flowing cold water or the like into the die, and the resin is solidified and then released. If there is a joint in the passage of the cooling water in this mold, an O-ring (a sealing ring made of a material such as rubber and having a circular cross section) is sandwiched between the mating surfaces to prevent leakage of the cooling water. The method of doing is general.

[0003]

In a mold in which leakage is prevented by such an O-ring, for example, when a thermal shock is applied to the sealing portion by a heating / cooling temperature cycle of injection molding, an O-ring material is required. Degradation is accelerated,
Cooling water may leak out relatively early. An object of the present invention is to provide an injection molding die that can reliably prevent leakage of cooling water even when exposed to such a thermal shock.

[0004]

According to the present invention, a transformation point is formed of a shape memory alloy whose temperature is set below a minimum temperature in a mold use or storage environment, and a memorized shape is larger than an inner diameter of a fluid passage. A cylindrical seal pipe having an outer diameter is prepared. Then, at the time of mold production, the seal pipe is cooled below the transformation point, plastically deformed into a shape that can pass through the fluid passage, and inserted so as to be located at a joint portion in the middle of the passage. Depending on the mold temperature,
The seal pipe is transformed into a memorized cylindrical shape beyond the transformation point and is sealed from the inner surface side of the passage.

[0005]

[Action] A seal pipe that has been plastically deformed by cooling
After moving in the fluid passage to reach the joint,
It transforms into a memorized cylindrical shape beyond the transformation point, and is pressed against its own outer peripheral surface or the inner peripheral surface of the fluid passage.

[0006]

An embodiment will be described with reference to the drawings. 1 and 2, 1 is a molded product, 2 is a fixed mold, 3 is a movable mold,
Reference numeral 4 denotes a first nest fixed to the movable mold 3 and 5 denotes a second nest fixed to the tip of the first nest 4. Second nest 5
Is formed of a material having a higher thermal conductivity than the first insert 3 in order to efficiently cool and solidify the high-temperature molten resin facing the cavity portion of the molded product 1 closer to the injection gate 10. I have. Numerals 30 and 31, 40, 41 and 50 denote fluid passages formed in the movable mold 3, the first nest 4 and the second nest 5, respectively. The upstream side of the passage 30 and the downstream side of the passage 31 are connected to a cooling medium circulating supply device (not shown).

The fluid passage 30 has an L-shape that changes its direction toward the first nest 4 on the way, and communicates with the fluid passage 40. The fluid passage 40 passes near the cavity portion and
To one end of the fluid passage 50 provided in the insert 5. The fluid passage 50 has an inverted U-shape. One end communicates with the above-described fluid passage 40, and the other end is connected to the fluid passage 41 provided in the first nest 4 in parallel with the fluid passage 40. Fluid passage 41
Also passes through the vicinity of the cavity and connects the fluid passage 50 of the second insert 5 to the fluid passage 31 of the movable mold 3. Fluid passage 3
The cooling medium 1 is also L-shaped and is formed back-to-back with the fluid passage 30, and the cooling medium is circulated and supplied to the movable mold 3, the first nest 4, and the second nest 5 by the fluid passages thus communicating with each other. , The mold will be cooled. The inner diameters of the joints between the fluid passages are equal to each other.

Reference numeral 6 denotes a seal pipe made of a shape memory alloy fitted to a joint between the fluid passages of the first nest 4 and the second nest 5. The fluid passages 40 and 41 connected to both ends of the passage 50 are arranged at two joints. FIG. 2 is an enlarged cross-sectional view of a main part of the joint portion.
Shows a state transformed into a stored shape. In forming the seal pipe 6, a martensitic transformation point is set below the minimum temperature in the mold use or storage environment, and the stored shape has an outer diameter slightly larger than the inner diameter of the joint portion of the fluid passage. The shape is cylindrical. That is, when the seal pipe 6 is cooled below the transformation point, it transforms into a martensite phase, and is easily plastically deformed into a shape capable of passing through the fluid passages 40 and 41. It has a thermal characteristic that transforms into a cylindrical shape and returns to the stored cylindrical shape. Transformation characteristics (shape memory characteristics) of such a shape memory alloy are well known, and therefore detailed description is omitted here.

The operation of the seal pipe in the mold will be described with reference to the drawings. The upper and lower views of FIG. 3 are plan views of the fluid passage 40 viewed from the movable mold 3 side, and respectively show a state when the seal pipe 6 is inserted and a state when the seal pipe 6 is sealed. At the time of mold production, the seal pipe 6 is cooled to a temperature lower than the transformation point, and the first nest 4 and the second nest 5 are moved to the movable mold 3.
Before fixing the first nest, the insertion operation is performed from the open ends of the first nested fluid passages 40 and 41. At this time, as shown in the upper diagram of FIG. 3, the seal pipe 6 is plastically deformed so as to be able to pass through the fluid passage 40 and is inserted so as to be located at a predetermined joint portion. After a while, the seal pipe 6 adapts to the surrounding mold temperature and rises in temperature, transforming from the martensite phase to the austenite phase. As a result of this transformation, the seal pipe 6 attempts to return to the memorized cylindrical shape as shown in the lower diagram of FIG. 3, and presses the entire inner peripheral surface of the joint portion of the fluid passages 40 and 50. With this shape recovery stress, the outer peripheral surface of the seal pipe 6 is pressed against the inner peripheral surfaces of the fluid passages 40 and 50, and the joint is sealed. Fluid passage 41
The same is done for the joints of 50 and 50,
Leakage of the cooling medium is prevented between the first nest and the second nest.

At the joint of the fluid passage between the movable mold 3 and the first insert 4, since the temperature change by injection molding is relatively small, sealing is performed by sandwiching an O-ring. Therefore, at the time of injection molding after closing the mold (FIG. 1), the cooling medium supplied from the cooling medium circulating supply device (not shown)
Without leaking, the movable mold 3 passes through the first nest 4 to reach the second nest 5, and after making a round in the second nest 5,
It returns to the cooling medium circulating supply device again through the first insert 4 and the movable mold 3, is cooled to a predetermined temperature, and is again returned to the second insert 5.
Supplied to. In this way, the cooling medium circulates through the second insert 5 formed of a material having a high thermal conductivity, the molten resin filled in the cavity is efficiently solidified, and the mold is opened and the molded article 1 is released. Will be

In this embodiment, the case where the joint portion between the inserts is sealed has been described. In addition, when the mold is cut out and the fluid passage is interrupted on the way, the dimension longer than this section length is used. The present invention can also be applied to a case where a seal pipe is prepared and transferred to a section that is interrupted, and both openings of the fluid passage are relay-sealed. Further, in addition to applications such as sealing of a joint portion, the present invention can also be used for applications where a hole that interferes with a fluid passage is erroneously formed during mold processing and the interference hole is closed and repaired. That is,
In the same manner as in the embodiment, a seal pipe having a size sufficient to cover the hole can be inserted into the portion of the hole that interferes to restore the shape, and the hole that has been opened in the fluid passage can be repaired and sealed.

[0012]

As described above, due to the shape memory characteristic that transforms at a lower temperature than during use and storage, the seal pipe is deformed and inserted, and the recovery stress to the memory shape is jointed as the pressure contact force to the inner peripheral surface of the fluid passage. Since the mating portion is sealed, leakage of the cooling water can be reliably prevented without deterioration even if the joint is exposed to a thermal shock in a range exceeding the transformation temperature. In addition, since the seal pipe can be moved to a portion to be sealed through the formed fluid passage, it is possible to avoid a situation in which the mold is divided and processed only for the purpose of sealing, and the degree of freedom of the mold design can be reduced. Is improved. Furthermore, in the case where a hole is accidentally made in the side wall of the fluid passage, the seal pipe can be inserted and repaired and sealed easily, so that the time for repairing the mold can be shortened.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view at the time of injection molding, showing an embodiment of an injection molding die of the present invention.

FIG. 2 is an enlarged sectional view of a main part during injection molding.

FIG. 3 is a plan view illustrating the operation of the seal pipe.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Molded product 2 Fixed mold 3 Moving mold 4 First insert 5 Second insert 30, 31, 40, 41, 50 Fluid passage 6 Seal pipe

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) B29C 45/26-45/44 B29C 33/00-33/76 B29C 45/73

Claims (2)

(57) [Claims] A fluid passage for cooling a molded product is formed in a mold, and when a seam portion present in the middle of the fluid passage is sealed from an inner surface side of the passage, a transformation point is set in a mold use or storage environment. A seal pipe made of a shape memory alloy set to be lower than the lowest temperature below and having a memorized shape having a cylindrical shape having an outer diameter larger than the inner diameter of the fluid passage is prepared. Cool the pipe below the transformation point, insert it so as to be plastically deformed into a shape that can pass through the fluid passage so as to be located at the seam,
An injection molding die, wherein the sealing pipe is transformed into a memorized cylindrical shape by exceeding a transformation point of the seal pipe depending on a surrounding mold temperature, and the joint portion is sealed. 2. A fluid passage for cooling a molded product is formed in a mold, and when an interference hole opened in a side wall of the fluid passage is closed from an inner surface side of the passage, a transformation point is determined in a use or storage environment of the mold. A seal pipe made of a shape memory alloy set at a temperature lower than the minimum temperature and having a stored shape that is a cylindrical shape having an outer diameter larger than the inner diameter of the fluid passage is prepared. Cooled below the transformation point, plastically deformed into a shape that can pass through the fluid passage and inserted so as to be located in the interference hole, and then, beyond the transformation point of the seal pipe, depending on the surrounding mold temperature. The injection molding die is characterized by being transformed into a stored cylindrical shape and sealing the interference hole.